proc — process information pseudo-filesystem
The proc filesystem is a
pseudo-filesystem which provides an interface to kernel data
structures. It is commonly mounted at /proc. Most of it is read-only, but some
files allow kernel variables to be changed.
The proc filesystem
supports the following mount options:
hidepid=n
(since Linux 3.3)This option controls who can access the
information in /proc/[pid] directories. The
argument, n, is one of
the following values:
0Everybody may access all
/proc/[pid]directories. This is the traditional behavior, and the default if this mount option is not specified.1Users may not access files and subdirectories inside any
/proc/[pid]directories but their own (the/proc/[pid]directories themselves remain visible). Sensitive files such as/proc/[pid]/cmdlineand/proc/[pid]/statusare now protected against other users. This makes it impossible to learn whether any user is running a specific program (so long as the program doesn't otherwise reveal itself by its behavior).2As for mode 1, but in addition the
/proc/[pid]directories belonging to other users become invisible. This means that/proc/[pid]entries can no longer be used to discover the PIDs on the system. This doesn't hide the fact that a process with a specific PID value exists (it can be learned by other means, for example, by "kill -0 $PID"), but it hides a process's UID and GID, which could otherwise be learned by employing stat(2) on a/proc/[pid]directory. This greatly complicates an attacker's task of gathering information about running processes (e.g., discovering whether some daemon is running with elevated privileges, whether another user is running some sensitive program, whether other users are running any program at all, and so on).
gid=gid
(since Linux 3.3)Specifies the ID of a group whose members are
authorized to learn process information otherwise
prohibited by hidepid
(i.e., users in this group behave as though
/proc was mounted with
hidepid=0).
This group should be used instead of approaches such
as putting nonroot users into the sudoers(5) file.
The following list describes many of the files and
directories under the /proc
hierarchy.
/proc/[pid]There is a numerical subdirectory for each running process; the subdirectory is named by the process ID. Each such subdirectory contains the following pseudo-files and directories.
/proc/[pid]/attrThe files in this directory provide an API for security modules. The contents of this directory are files that can be read and written in order to set security-related attributes. This directory was added to support SELinux, but the intention was that the API be general enough to support other security modules. For the purpose of explanation, examples of how SELinux uses these files are provided below.
This directory is present only if the kernel was
configured with CONFIG_SECURITY.
/proc/[pid]/attr/current (since Linux
2.6.0)The contents of this file represent the current security attributes of the process.
In SELinux, this file is used to get the security
context of a process. Prior to Linux 2.6.11, this
file could not be used to set the security context (a
write was always denied), since SELinux limited
process security transitions to execve(2) (see the
description of /proc/[pid]/attr/exec, below).
Since Linux 2.6.11, SELinux lifted this restriction
and began supporting "set" operations via writes to
this node if authorized by policy, although use of
this operation is only suitable for applications that
are trusted to maintain any desired separation
between the old and new security contexts. Prior to
Linux 2.6.28, SELinux did not allow threads within a
multi-threaded process to set their security context
via this node as it would yield an inconsistency
among the security contexts of the threads sharing
the same memory space. Since Linux 2.6.28, SELinux
lifted this restriction and began supporting "set"
operations for threads within a multithreaded process
if the new security context is bounded by the old
security context, where the bounded relation is
defined in policy and guarantees that the new
security context has a subset of the permissions of
the old security context. Other security modules may
choose to support "set" operations via writes to this
node.
/proc/[pid]/attr/exec (since Linux
2.6.0)This file represents the attributes to assign to the process upon a subsequent execve(2).
In SELinux, this is needed to support role/domain
transitions, and execve(2) is the
preferred point to make such transitions because it
offers better control over the initialization of the
process in the new security label and the inheritance
of state. In SELinux, this attribute is reset on
execve(2) so that
the new program reverts to the default behavior for
any execve(2) calls
that it may make. In SELinux, a process can set only
its own /proc/[pid]/attr/exec
attribute.
/proc/[pid]/attr/fscreate (since
Linux 2.6.0)This file represents the attributes to assign to files created by subsequent calls to open(2), mkdir(2), symlink(2), and mknod(2)
SELinux employs this file to support creation of a
file (using the aforementioned system calls) in a
secure state, so that there is no risk of
inappropriate access being obtained between the time
of creation and the time that attributes are set. In
SELinux, this attribute is reset on execve(2), so that
the new program reverts to the default behavior for
any file creation calls it may make, but the
attribute will persist across multiple file creation
calls within a program unless it is explicitly reset.
In SELinux, a process can set only its own
/proc/[pid]/attr/fscreate
attribute.
/proc/[pid]/attr/prev (since Linux
2.6.0)This file contains the security context of the
process before the last execve(2); that is,
the previous value of /proc/[pid]/attr/current.
/proc/[pid]/attr/keycreate (since
Linux 2.6.18)If a process writes a security context into this
file, all subsequently created keys (add_key(2)) will be
labeled with this context. For further information,
see the kernel source file Documentation/keys.txt.
/proc/[pid]/attr/socketcreate (since
Linux 2.6.18)If a process writes a security context into this file, all subsequently created sockets will be labeled with this context.
/proc/[pid]/auxv (since
2.6.0-test7)This contains the contents of the ELF interpreter information passed to the process at exec time. The format is one unsigned long ID plus one unsigned long value for each entry. The last entry contains two zeros. See also getauxval(3).
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/cgroup (since Linux
2.6.24)See cgroups(7).
/proc/[pid]/clear_refs (since Linux
2.6.22)This is a write-only file, writable only by owner of the process.
The following values may be written to the file:
- 1 (since Linux 2.6.22)
Reset the PG_Referenced and ACCESSED/YOUNG bits for all the pages associated with the process. (Before kernel 2.6.32, writing any nonzero value to this file had this effect.)
- 2 (since Linux 2.6.32)
Reset the PG_Referenced and ACCESSED/YOUNG bits for all anonymous pages associated with the process.
- 3 (since Linux 2.6.32)
Reset the PG_Referenced and ACCESSED/YOUNG bits for all file-mapped pages associated with the process.
Clearing the PG_Referenced and ACCESSED/YOUNG bits
provides a method to measure approximately how much
memory a process is using. One first inspects the
values in the "Referenced" fields for the VMAs shown
in /proc/[pid]/smaps to
get an idea of the memory footprint of the process.
One then clears the PG_Referenced and ACCESSED/YOUNG
bits and, after some measured time interval, once
again inspects the values in the "Referenced" fields
to get an idea of the change in memory footprint of
the process during the measured interval. If one is
interested only in inspecting the selected mapping
types, then the value 2 or 3 can be used instead of
1.
A further value can be written to affect a different bit:
- 4 (since Linux 3.11)
Clear the soft-dirty bit for all the pages associated with the process. This is used (in conjunction with
/proc/[pid]/pagemap) by the check-point restore system to discover which pages of a process have been dirtied since the file/proc/[pid]/clear_refswas written to.
Writing any value to /proc/[pid]/clear_refs other than
those listed above has no effect.
The /proc/[pid]/clear_refs file is
present only if the CONFIG_PROC_PAGE_MONITOR kernel
configuration option is enabled.
/proc/[pid]/cmdlineThis read-only file holds the complete command line for the process, unless the process is a zombie. In the latter case, there is nothing in this file: that is, a read on this file will return 0 characters. The command-line arguments appear in this file as a set of strings separated by null bytes ('\0'), with a further null byte after the last string.
/proc/[pid]/comm (since Linux
2.6.33)This file exposes the process's comm value—that is, the
command name associated with the process. Different
threads in the same process may have different
comm values, accessible
via /proc/[pid]/task/[tid]/comm. A
thread may modify its comm value, or that of any of other
thread in the same thread group (see the discussion
of CLONE_THREAD in
clone(2)), by
writing to the file /proc/self/task/[tid]/comm. Strings
longer than TASK_COMM_LEN (16) characters are
silently truncated.
This file provides a superset of the prctl(2)
PR_SET_NAME and
PR_GET_NAME operations,
and is employed by pthread_setname_np(3)
when used to rename threads other than the
caller.
/proc/[pid]/coredump_filter (since
Linux 2.6.23)See core(5).
/proc/[pid]/cpuset (since Linux
2.6.12)See cpuset(7).
/proc/[pid]/cwdThis is a symbolic link to the current working directory of the process. To find out the current working directory of process 20, for instance, you can do this:
$ cd /proc/20/cwd; /bin/pwd
Note that the pwd command is often a shell built-in, and might not work properly. In bash(1), you may use pwd −P.
In a multithreaded process, the contents of this symbolic link are not available if the main thread has already terminated (typically by calling pthread_exit(3)).
Permission to dereference or read (readlink(2)) this
symbolic link is governed by a ptrace access mode
PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/environThis file contains the environment for the process. The entries are separated by null bytes ('\0'), and there may be a null byte at the end. Thus, to print out the environment of process 1, you would do:
$ strings /proc/1/environ
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/exeUnder Linux 2.2 and later, this file is a symbolic
link containing the actual pathname of the executed
command. This symbolic link can be dereferenced
normally; attempting to open it will open the
executable. You can even type /proc/[pid]/exe to run another copy
of the same executable that is being run by process
[pid]. If the pathname has been unlinked, the
symbolic link will contain the string '(deleted)'
appended to the original pathname. In a multithreaded
process, the contents of this symbolic link are not
available if the main thread has already terminated
(typically by calling pthread_exit(3)).
Permission to dereference or read (readlink(2)) this
symbolic link is governed by a ptrace access mode
PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the
binary which was executed, and appears as a symbolic
link. A readlink(2) call on
this file under Linux 2.0 returns a string in the
format:
[device]:inode
For example, [0301]:1502 would be inode 1502 on device major 03 (IDE, MFM, etc. drives) minor 01 (first partition on the first drive).
find(1) with the
−inum option can be
used to locate the file.
/proc/[pid]/fd/This is a subdirectory containing one entry for each file which the process has open, named by its file descriptor, and which is a symbolic link to the actual file. Thus, 0 is standard input, 1 standard output, 2 standard error, and so on.
For file descriptors for pipes and sockets, the entries will be symbolic links whose content is the file type with the inode. A readlink(2) call on this file returns a string in the format:
type:[inode]
For example, socket:[2248868] will
be a socket and its inode is 2248868. For sockets,
that inode can be used to find more information in
one of the files under /proc/net/.
For file descriptors that have no corresponding inode (e.g., file descriptors produced by epoll_create(2), eventfd(2), inotify_init(2), signalfd(2), and timerfd(2)), the entry will be a symbolic link with contents of the form
anon_inode:<file-type>
In some cases, the file-type is
surrounded by square brackets.
For example, an epoll file descriptor will have a
symbolic link whose content is the string anon_inode:[eventpoll].
In a multithreaded process, the contents of this directory are not available if the main thread has already terminated (typically by calling pthread_exit(3)).
Programs that will take a filename as a
command-line argument, but will not take input from
standard input if no argument is supplied, or that
write to a file named as a command-line argument, but
will not send their output to standard output if no
argument is supplied, can nevertheless be made to use
standard input or standard out using /proc/[pid]/fd. For example,
assuming that −i is
the flag designating an input file and −o is the flag designating an
output file:
$ foobar −i /proc/self/fd/0 −o /proc/self/fd/1 ...
and you have a working filter.
/proc/self/fd/N is
approximately the same as /dev/fd/N in some UNIX and
UNIX-like systems. Most Linux MAKEDEV scripts
symbolically link /dev/fd to /proc/self/fd, in fact.
Most systems provide symbolic links /dev/stdin, /dev/stdout, and /dev/stderr, which respectively
link to the files 0,
1, and 2 in /proc/self/fd. Thus the example
command above could be written as:
$ foobar −i /dev/stdin −o /dev/stdout ...
Permission to dereference or read (readlink(2)) the
symbolic links in this directory is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/fdinfo/ (since Linux
2.6.22)This is a subdirectory containing one entry for each file which the process has open, named by its file descriptor. The files in this directory are readable only by the owner of the process. The contents of each file can be read to obtain information about the corresponding file descriptor. The content depends on the type of file referred to by the corresponding file descriptor.
For regular files and directories, we see something like:
$ cat /proc/12015/fdinfo/4 pos: 1000 flags: 01002002 mnt_id: 21
The fields are as follows:
posThis is a decimal number showing the file offset.
flagsThis is an octal number that displays the file access mode and file status flags (see open(2)). If the close-on-exec file descriptor flag is set, then
flagswill also include the valueO_CLOEXEC.Before Linux 3.1, this field incorrectly displayed the setting of
O_CLOEXECat the time the file was opened, rather than the current setting of the close-on-exec flag.
mnt_idThis field, present since Linux 3.15, is the ID of the mount point containing this file. See the description of/proc/[pid]/mountinfo.
For eventfd file descriptors (see eventfd(2)), we see (since Linux 3.8) the following fields:
pos: 0 flags: 02 mnt_id: 10 eventfd-count: 40
eventfd-count is the
current value of the eventfd counter, in
hexadecimal.
For epoll file descriptors (see epoll(7)), we see (since Linux 3.8) the following fields:
pos: 0 flags: 02 mnt_id: 10 tfd: 9 events: 19 data: 74253d2500000009 tfd: 7 events: 19 data: 74253d2500000007
Each of the lines beginning tfd describes one of the file
descriptors being monitored via the epoll file
descriptor (see epoll_ctl(2) for
some details). The tfd
field is the number of the file descriptor. The
events field is a
hexadecimal mask of the events being monitored for
this file descriptor. The data field is the data value
associated with this file descriptor.
For signalfd file descriptors (see signalfd(2)), we see (since Linux 3.8) the following fields:
pos: 0 flags: 02 mnt_id: 10 sigmask: 0000000000000006
sigmask is the
hexadecimal mask of signals that are accepted via
this signalfd file descriptor. (In this example, bits
2 and 3 are set, corresponding to the signals
SIGINT and SIGQUIT; see signal(7).)
For inotify file descriptors (see inotify(7)), we see (since Linux 3.8) the following fields:
pos: 0 flags: 00 mnt_id: 11 inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73 inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73
Each of the lines beginning with "inotify" displays information about one file or directory that is being monitored. The fields in this line are as follows:
wdA watch descriptor number (in decimal).
inoThe inode number of the target file (in hexadecimal).
sdevThe ID of the device where the target file resides (in hexadecimal).
maskThe mask of events being monitored for the target file (in hexadecimal).
If the kernel was built with exportfs support, the
path to the target file is exposed as a file handle,
via three hexadecimal fields: fhandle-bytes,
fhandle-type, and
f_handle.
For fanotify file descriptors (see fanotify(7)), we see (since Linux 3.8) the following fields:
pos: 0 flags: 02 mnt_id: 11 fanotify flags:0 event-flags:88002 fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73
The fourth line displays information defined when the fanotify group was created via fanotify_init(2):
flagsThe
flagsargument given to fanotify_init(2) (expressed in hexadecimal).event-flagsThe
event_f_flagsargument given to fanotify_init(2) (expressed in hexadecimal).
Each additional line shown in the file contains information about one of the marks in the fanotify group. Most of these fields are as for inotify, except:
mflagsThe flags associated with the mark (expressed in hexadecimal).
maskThe events mask for this mark (expressed in hexadecimal).
ignored_maskThe mask of events that are ignored for this mark (expressed in hexadecimal).
For details on these fields, see fanotify_mark(2).
/proc/[pid]/io (since kernel
2.6.20)This file contains I/O statistics for the process, for example:
# cat /proc/3828/io rchar: 323934931 wchar: 323929600 syscr: 632687 syscw: 632675 read_bytes: 0 write_bytes: 323932160 cancelled_write_bytes: 0
The fields are as follows:
rchar: characters readThe number of bytes which this task has caused to be read from storage. This is simply the sum of bytes which this process passed to read(2) and similar system calls. It includes things such as terminal I/O and is unaffected by whether or not actual physical disk I/O was required (the read might have been satisfied from pagecache).
wchar: characters writtenThe number of bytes which this task has caused, or shall cause to be written to disk. Similar caveats apply here as with
rchar.syscr: read syscallsAttempt to count the number of read I/O operations—that is, system calls such as read(2) and pread(2).
syscw: write syscallsAttempt to count the number of write I/O operations—that is, system calls such as write(2) and pwrite(2).
read_bytes: bytes readAttempt to count the number of bytes which this process really did cause to be fetched from the storage layer. This is accurate for block-backed filesystems.
write_bytes: bytes writtenAttempt to count the number of bytes which this process caused to be sent to the storage layer.
cancelled_write_bytes:The big inaccuracy here is truncate. If a process writes 1MB to a file and then deletes the file, it will in fact perform no writeout. But it will have been accounted as having caused 1MB of write. In other words: this field represents the number of bytes which this process caused to not happen, by truncating pagecache. A task can cause "negative" I/O too. If this task truncates some dirty pagecache, some I/O which another task has been accounted for (in its
write_bytes) will not be happening.
Note: In the current
implementation, things are a bit racy on 32-bit
systems: if process A reads process B's /proc/[pid]/io while process B is
updating one of these 64-bit counters, process A
could see an intermediate result.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/gid_map (since Linux
3.5)See user_namespaces(7).
/proc/[pid]/limits (since Linux
2.6.24)This file displays the soft limit, hard limit, and units of measurement for each of the process's resource limits (see getrlimit(2)). Up to and including Linux 2.6.35, this file is protected to allow reading only by the real UID of the process. Since Linux 2.6.36, this file is readable by all users on the system.
/proc/[pid]/map_files/ (since kernel
3.3)This subdirectory contains entries corresponding to memory-mapped files (see mmap(2)). Entries are named by memory region start and end address pair (expressed as hexadecimal numbers), and are symbolic links to the mapped files themselves. Here is an example, with the output wrapped and reformatted to fit on an 80-column display:
# ls -l /proc/self/map_files/ lr−−−−−−−−. 1 root root 64 Apr 16 21:31 3252e00000−3252e20000 −> /usr/lib64/ld-2.15.so ...
Although these entries are present for memory
regions that were mapped with the MAP_FILE flag, the way anonymous
shared memory (regions created with the MAP_ANON | MAP_SHARED
flags) is implemented in Linux means that such
regions also appear on this directory. Here is an
example where the target file is the deleted
/dev/zero one:
lrw−−−−−−−. 1 root root 64 Apr 16 21:33 7fc075d2f000−7fc075e6f000 −> /dev/zero (deleted)
This directory appears only if the CONFIG_CHECKPOINT_RESTORE kernel
configuration option is enabled. Privilege
(CAP_SYS_ADMIN) is
required to view the contents of this directory.
/proc/[pid]/mapsA file containing the currently mapped memory regions and their access permissions. See mmap(2) for some further information about memory mappings.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
The format of the file is:
address perms offset dev inode pathname 00400000-00452000 r-xp 00000000 08:02 173521 /usr/bin/dbus-daemon 00651000-00652000 r--p 00051000 08:02 173521 /usr/bin/dbus-daemon 00652000-00655000 rw-p 00052000 08:02 173521 /usr/bin/dbus-daemon 00e03000-00e24000 rw-p 00000000 00:00 0 [heap] 00e24000-011f7000 rw-p 00000000 00:00 0 [heap] ... 35b1800000-35b1820000 r-xp 00000000 08:02 135522 /usr/lib64/ld-2.15.so 35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522 /usr/lib64/ld-2.15.so 35b1a20000-35b1a21000 rw-p 00020000 08:02 135522 /usr/lib64/ld-2.15.so 35b1a21000-35b1a22000 rw-p 00000000 00:00 0 35b1c00000-35b1dac000 r-xp 00000000 08:02 135870 /usr/lib64/libc-2.15.so 35b1dac000-35b1fac000 ---p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so 35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so 35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870 /usr/lib64/libc-2.15.so ... f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0 [stack:986] ... 7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0 [stack] 7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0 [vdso]
The address field is
the address space in the process that the mapping
occupies. The perms
field is a set of permissions:
r = read w = write x = execute s = shared p = private (copy on write)
The offset field is
the offset into the file/whatever; dev is the device (major:minor);
inode is the inode on
that device. 0 indicates that no inode is associated
with the memory region, as would be the case with BSS
(uninitialized data).
The pathname field
will usually be the file that is backing the mapping.
For ELF files, you can easily coordinate with the
offset field by looking
at the Offset field in the ELF program headers
(readelf
−l).
There are additional helpful pseudo-paths:
[stack]The initial process's (also known as the main thread's) stack.
[stack:<tid>](since Linux 3.4)A thread's stack (where the
<tid>is a thread ID). It corresponds to the/proc/[pid]/task/[tid]/path.[vdso]The virtual dynamically linked shared object.
[heap]The process's heap.
If the pathname field
is blank, this is an anonymous mapping as obtained
via the mmap(2) function.
There is no easy way to coordinate this back to a
process's source, short of running it through
gdb(1), strace(1), or
similar.
Under Linux 2.0, there is no field giving pathname.
/proc/[pid]/memThis file can be used to access the pages of a process's memory through open(2), read(2), and lseek(2).
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check;
see ptrace(2).
/proc/[pid]/mountinfo (since Linux
2.6.26)This file contains information about mount points
in the process's mount namespace (see mount_namespaces(7)).
It supplies various information (e.g., propagation
state, root of mount for bind mounts, identifier for
each mount and its parent) that is missing from the
(older) /proc/[pid]/mounts file, and fixes
various other problems with that file (e.g.,
nonextensibility, failure to distinguish per-mount
versus per-superblock options).
The file contains lines of the form:
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 − ext3 /dev/root rw,errors=continue (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
The numbers in parentheses are labels for the descriptions below:
- (1)
mount ID: a unique ID for the mount (may be reused after umount(2)).
- (2)
parent ID: the ID of the parent mount (or of self for the top of the mount tree).
- (3)
major:minor: the value of
st_devfor files on this filesystem (see stat(2)).- (4)
root: the pathname of the directory in the filesystem which forms the root of this mount.
- (5)
mount point: the pathname of the mount point relative to the process's root directory.
- (6)
mount options: per-mount options.
- (7)
optional fields: zero or more fields of the form "tag[:value]"; see below.
- (8)
separator: the end of the optional fields is marked by a single hyphen.
- (9)
filesystem type: the filesystem type in the form "type[.subtype]".
- (10)
mount source: filesystem-specific information or "none".
- (11)
super options: per-superblock options.
Currently, the possible optional fields are
shared, master, propagate_from, and unbindable. See mount_namespaces(7)
for a description of these fields. Parsers should
ignore all unrecognized optional fields.
For more information on mount propagation see:
Documentation/filesystems/sharedsubtree.txt
in the Linux kernel source tree.
/proc/[pid]/mounts (since Linux
2.4.19)This file lists all the filesystems currently mounted in the process's mount namespace (see mount_namespaces(7)). The format of this file is documented in fstab(5).
Since kernel version 2.6.15, this file is
pollable: after opening the file for reading, a
change in this file (i.e., a filesystem mount or
unmount) causes select(2) to mark
the file descriptor as having an exceptional
condition, and poll(2) and
epoll_wait(2) mark
the file as having a priority event (POLLPRI). (Before Linux 2.6.30, a
change in this file was indicated by the file
descriptor being marked as readable for select(2), and
being marked as having an error condition for
poll(2) and
epoll_wait(2).)
/proc/[pid]/mountstats (since Linux
2.6.17)This file exports information (statistics, configuration information) about the mount points in the process's mount namespace (see mount_namespaces(7)). Lines in this file have the form:
device /dev/sda7 mounted on /home with fstype ext3 [statistics] ( 1 ) ( 2 ) (3 ) (4)
The fields in each line are:
- (1)
The name of the mounted device (or "nodevice" if there is no corresponding device).
- (2)
The mount point within the filesystem tree.
- (3)
The filesystem type.
- (4)
Optional statistics and configuration information. Currently (as at Linux 2.6.26), only NFS filesystems export information via this field.
This file is readable only by the owner of the process.
/proc/[pid]/net " (since Linux 2.6.25)" See the
description of /proc/net.
/proc/[pid]/ns/ (since Linux
3.0)This is a subdirectory containing one entry for each namespace that supports being manipulated by setns(2). For more information, see namespaces(7).
/proc/[pid]/numa_maps (since Linux
2.6.14)See numa(7).
/proc/[pid]/oom_adj (since Linux
2.6.11)This file can be used to adjust the score used to
select which process should be killed in an
out-of-memory (OOM) situation. The kernel uses this
value for a bit-shift operation of the process's
oom_score value: valid
values are in the range −16 to +15, plus the
special value −17, which disables OOM-killing
altogether for this process. A positive score
increases the likelihood of this process being killed
by the OOM-killer; a negative score decreases the
likelihood.
The default value for this file is 0; a new
process inherits its parent's oom_adj setting. A process must be
privileged (CAP_SYS_RESOURCE) to update this
file.
Since Linux 2.6.36, use of this file is deprecated
in favor of /proc/[pid]/oom_score_adj.
/proc/[pid]/oom_score (since Linux
2.6.11)This file displays the current score that the kernel gives to this process for the purpose of selecting a process for the OOM-killer. A higher score means that the process is more likely to be selected by the OOM-killer. The basis for this score is the amount of memory used by the process, with increases (+) or decreases (−) for factors including:
whether the process creates a lot of children using fork(2) (+);
whether the process has been running a long time, or has used a lot of CPU time (−);
whether the process has a low nice value (i.e., > 0) (+);
whether the process is privileged (−); and
whether the process is making direct hardware access (−).
The oom_score also
reflects the adjustment specified by the oom_score_adj or oom_adj setting for the process.
/proc/[pid]/oom_score_adj (since
Linux 2.6.36)This file can be used to adjust the badness heuristic used to select which process gets killed in out-of-memory conditions.
The badness heuristic assigns a value to each candidate task ranging from 0 (never kill) to 1000 (always kill) to determine which process is targeted. The units are roughly a proportion along that range of allowed memory the process may allocate from, based on an estimation of its current memory and swap use. For example, if a task is using all allowed memory, its badness score will be 1000. If it is using half of its allowed memory, its score will be 500.
There is an additional factor included in the badness score: root processes are given 3% extra memory over other tasks.
The amount of "allowed" memory depends on the context in which the OOM-killer was called. If it is due to the memory assigned to the allocating task's cpuset being exhausted, the allowed memory represents the set of mems assigned to that cpuset (see cpuset(7)). If it is due to a mempolicy's node(s) being exhausted, the allowed memory represents the set of mempolicy nodes. If it is due to a memory limit (or swap limit) being reached, the allowed memory is that configured limit. Finally, if it is due to the entire system being out of memory, the allowed memory represents all allocatable resources.
The value of oom_score_adj is added to the
badness score before it is used to determine which
task to kill. Acceptable values range from
−1000 (OOM_SCORE_ADJ_MIN) to +1000
(OOM_SCORE_ADJ_MAX). This allows user space to
control the preference for OOM-killing, ranging from
always preferring a certain task or completely
disabling it from OOM killing. The lowest possible
value, −1000, is equivalent to disabling
OOM-killing entirely for that task, since it will
always report a badness score of 0.
Consequently, it is very simple for user space to
define the amount of memory to consider for each
task. Setting a oom_score_adj value of +500, for
example, is roughly equivalent to allowing the
remainder of tasks sharing the same system, cpuset,
mempolicy, or memory controller resources to use at
least 50% more memory. A value of −500, on the
other hand, would be roughly equivalent to
discounting 50% of the task's allowed memory from
being considered as scoring against the task.
For backward compatibility with previous kernels,
/proc/[pid]/oom_adj can
still be used to tune the badness score. Its value is
scaled linearly with oom_score_adj.
Writing to /proc/[pid]/oom_score_adj or
/proc/[pid]/oom_adj
will change the other with its scaled value.
/proc/[pid]/pagemap (since Linux
2.6.25)This file shows the mapping of each of the process's virtual pages into physical page frames or swap area. It contains one 64-bit value for each virtual page, with the bits set as follows:
63If set, the page is present in RAM.
62If set, the page is in swap space
- 61 (since Linux 3.5)
The page is a file-mapped page or a shared anonymous page.
- 60-56 (since Linux 3.11)
Zero
- 55 (Since Linux 3.11)
PTE is soft-dirty (see the kernel source file
Documentation/vm/soft-dirty.txt).- 54-0
If the page is present in RAM (bit 63), then these bits provide the page frame number, which can be used to index
/proc/kpageflagsand/proc/kpagecount. If the page is present in swap (bit 62), then bits 4-0 give the swap type, and bits 54-5 encode the swap offset.
Before Linux 3.11, bits 60-55 were used to encode the base-2 log of the page size.
To employ /proc/[pid]/pagemap efficiently,
use /proc/[pid]/maps to
determine which areas of memory are actually mapped
and seek to skip over unmapped regions.
The /proc/[pid]/pagemap file is present
only if the CONFIG_PROC_PAGE_MONITOR kernel
configuration option is enabled.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/personality (since Linux
2.6.28)This read-only file exposes the process's execution domain, as set by personality(2). The value is displayed in hexadecimal notation.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check;
see ptrace(2).
/proc/[pid]/rootUNIX and Linux support the idea of a per-process
root of the filesystem, set by the chroot(2) system
call. This file is a symbolic link that points to the
process's root directory, and behaves in the same way
as exe, and fd/*.
In a multithreaded process, the contents of this symbolic link are not available if the main thread has already terminated (typically by calling pthread_exit(3)).
Permission to dereference or read (readlink(2)) this
symbolic link is governed by a ptrace access mode
PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/[pid]/seccomp (from Linux 2.6.12 to
2.6.22)Read/set the seccomp mode for the process. If this file contains the value zero, seccomp mode is not enabled. Writing the value 1 to this file (irreversibly) places the process in seccomp mode: the only permitted system calls are read(2), write(2), _exit(2), and sigreturn(2). This file went away in Linux 2.6.23, when it was replaced by a prctl(2)-based mechanism.
/proc/[pid]/setgroups (since Linux
3.19)See user_namespaces(7).
/proc/[pid]/smaps (since Linux
2.6.14)This file shows memory consumption for each of the process's mappings. (The pmap(1) command displays similar information, in a form that may be easier for parsing.) For each mapping there is a series of lines such as the following:
00400000-0048a000 r-xp 00000000 fd:03 960637 /bin/bash Size: 552 kB Rss: 460 kB Pss: 100 kB Shared_Clean: 452 kB Shared_Dirty: 0 kB Private_Clean: 8 kB Private_Dirty: 0 kB Referenced: 460 kB Anonymous: 0 kB AnonHugePages: 0 kB Swap: 0 kB KernelPageSize: 4 kB MMUPageSize: 4 kB Locked: 0 kB
The first of these lines shows the same
information as is displayed for the mapping in
/proc/[pid]/maps. The
remaining lines show the size of the mapping, the
amount of the mapping that is currently resident in
RAM ("Rss"), the process' proportional share of this
mapping ("Pss"), the number of clean and dirty shared
pages in the mapping, and the number of clean and
dirty private pages in the mapping. "Referenced"
indicates the amount of memory currently marked as
referenced or accessed. "Anonymous" shows the amount
of memory that does not belong to any file. "Swap"
shows how much would-be-anonymous memory is also
used, but out on swap.
The "KernelPageSize" entry is the page size used by the kernel to back a VMA. This matches the size used by the MMU in the majority of cases. However, one counter-example occurs on PPC64 kernels whereby a kernel using 64K as a base page size may still use 4K pages for the MMU on older processors. To distinguish, this patch reports "MMUPageSize" as the page size used by the MMU.
The "Locked" indicates whether the mapping is locked in memory or not.
"VmFlags" field represents the kernel flags associated with the particular virtual memory area in two letter encoded manner. The codes are the following:
rd - readable
wr - writable
ex - executable
sh - shared
mr - may read
mw - may write
me - may execute
ms - may share
gd - stack segment grows down
pf - pure PFN range
dw - disabled write to the mapped file
lo - pages are locked in memory
io - memory mapped I/O area
sr - sequential read advise provided
rr - random read advise provided
dc - do not copy area on fork
de - do not expand area on remapping
ac - area is accountable
nr - swap space is not reserved for the area
ht - area uses huge tlb pages
nl - non-linear mapping
ar - architecture specific flag
dd - do not include area into core dump
sd - soft-dirty flag
mm - mixed map area
hg - huge page advise flag
nh - no-huge page advise flag
mg - mergeable advise flag
The /proc/[pid]/smaps file is present
only if the CONFIG_PROC_PAGE_MONITOR kernel
configuration option is enabled.
/proc/[pid]/stack (since Linux
2.6.29)This file provides a symbolic trace of the
function calls in this process's kernel stack. This
file is provided only if the kernel was built with
the CONFIG_STACKTRACE
configuration option.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check;
see ptrace(2).
/proc/[pid]/statStatus information about the process. This is used
by ps(1). It is defined in
the kernel source file fs/proc/array.c.
The fields, in order, with their proper scanf(3) format
specifiers, are listed below. Whether or not certain
of these fields display valid information is governed
by a ptrace access mode PTRACE_MODE_READ_FSCREDS |
PTRACE_MODE_NOAUDIT
check (refer to ptrace(2)). If the
check denies access, then the field value is
displayed as 0. The affected fields are indicated
with the marking [PT].
- (1)
pid%dThe process ID.
- (2)
comm%sThe filename of the executable, in parentheses. This is visible whether or not the executable is swapped out.
- (3)
state%cOne of the following characters, indicating process state:
RRunning
SSleeping in an interruptible wait
DWaiting in uninterruptible disk sleep
ZZombie
TStopped (on a signal) or (before Linux 2.6.33) trace stopped
tTracing stop (Linux 2.6.33 onward)
WPaging (only before Linux 2.6.0)
XDead (from Linux 2.6.0 onward)
xDead (Linux 2.6.33 to 3.13 only)
KWakekill (Linux 2.6.33 to 3.13 only)
WWaking (Linux 2.6.33 to 3.13 only)
PParked (Linux 3.9 to 3.13 only)
- (4)
ppid%dThe PID of the parent of this process.
- (5)
pgrp%dThe process group ID of the process.
- (6)
session%dThe session ID of the process.
- (7)
tty_nr%dThe controlling terminal of the process. (The minor device number is contained in the combination of bits 31 to 20 and 7 to 0; the major device number is in bits 15 to 8.)
- (8)
tpgid%dThe ID of the foreground process group of the controlling terminal of the process.
- (9)
flags%uThe kernel flags word of the process. For bit meanings, see the PF_* defines in the Linux kernel source file
include/linux/sched.h. Details depend on the kernel version.The format for this field was %lu before Linux 2.6.
- (10)
minflt%luThe number of minor faults the process has made which have not required loading a memory page from disk.
- (11)
cminflt%luThe number of minor faults that the process's waited-for children have made.
- (12)
majflt%luThe number of major faults the process has made which have required loading a memory page from disk.
- (13)
cmajflt%luThe number of major faults that the process's waited-for children have made.
- (14)
utime%luAmount of time that this process has been scheduled in user mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)). This includes guest time,guest_time(time spent running a virtual CPU, see below), so that applications that are not aware of the guest time field do not lose that time from their calculations.- (15)
stime%luAmount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).- (16)
cutime%ldAmount of time that this process's waited-for children have been scheduled in user mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)). (See also times(2).) This includes guest time,cguest_time(time spent running a virtual CPU, see below).- (17)
cstime%ldAmount of time that this process's waited-for children have been scheduled in kernel mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).- (18)
priority%ld(Explanation for Linux 2.6) For processes running a real-time scheduling policy (
policybelow; see sched_setscheduler(2)), this is the negated scheduling priority, minus one; that is, a number in the range −2 to −100, corresponding to real-time priorities 1 to 99. For processes running under a non-real-time scheduling policy, this is the raw nice value (setpriority(2)) as represented in the kernel. The kernel stores nice values as numbers in the range 0 (high) to 39 (low), corresponding to the user-visible nice range of −20 to 19.Before Linux 2.6, this was a scaled value based on the scheduler weighting given to this process.
- (19)
nice%ldThe nice value (see setpriority(2)), a value in the range 19 (low priority) to −20 (high priority).
- (20)
num_threads%ldNumber of threads in this process (since Linux 2.6). Before kernel 2.6, this field was hard coded to 0 as a placeholder for an earlier removed field.
- (21)
itrealvalue%ldThe time in jiffies before the next
SIGALRMis sent to the process due to an interval timer. Since kernel 2.6.17, this field is no longer maintained, and is hard coded as 0.- (22)
starttime%lluThe time the process started after system boot. In kernels before Linux 2.6, this value was expressed in jiffies. Since Linux 2.6, the value is expressed in clock ticks (divide by
sysconf(_SC_CLK_TCK)).The format for this field was %lu before Linux 2.6.
- (23)
vsize%luVirtual memory size in bytes.
- (24)
rss%ldResident Set Size: number of pages the process has in real memory. This is just the pages which count toward text, data, or stack space. This does not include pages which have not been demand-loaded in, or which are swapped out.
- (25)
rsslim%luCurrent soft limit in bytes on the rss of the process; see the description of
RLIMIT_RSSin getrlimit(2).- (26)
startcode%lu [PT]The address above which program text can run.
- (27)
endcode%lu [PT]The address below which program text can run.
- (28)
startstack%lu [PT]The address of the start (i.e., bottom) of the stack.
- (29)
kstkesp%lu [PT]The current value of ESP (stack pointer), as found in the kernel stack page for the process.
- (30)
kstkeip%lu [PT]The current EIP (instruction pointer).
- (31)
signal%luThe bitmap of pending signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/statusinstead.- (32)
blocked%luThe bitmap of blocked signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/statusinstead.- (33)
sigignore%luThe bitmap of ignored signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/statusinstead.- (34)
sigcatch%luThe bitmap of caught signals, displayed as a decimal number. Obsolete, because it does not provide information on real-time signals; use
/proc/[pid]/statusinstead.- (35)
wchan%lu [PT]This is the "channel" in which the process is waiting. It is the address of a location in the kernel where the process is sleeping. The corresponding symbolic name can be found in
/proc/[pid]/wchan.- (36)
nswap%luNumber of pages swapped (not maintained).
- (37)
cnswap%luCumulative
nswapfor child processes (not maintained).- (38)
exit_signal%d (since Linux 2.1.22)Signal to be sent to parent when we die.
- (39)
processor%d (since Linux 2.2.8)CPU number last executed on.
- (40)
rt_priority%u (since Linux 2.5.19)Real-time scheduling priority, a number in the range 1 to 99 for processes scheduled under a real-time policy, or 0, for non-real-time processes (see sched_setscheduler(2)).
- (41)
policy%u (since Linux 2.5.19)Scheduling policy (see sched_setscheduler(2)). Decode using the SCHED_* constants in
linux/sched.h.The format for this field was %lu before Linux 2.6.22.
- (42)
delayacct_blkio_ticks%llu (since Linux 2.6.18)Aggregated block I/O delays, measured in clock ticks (centiseconds).
- (43)
guest_time%lu (since Linux 2.6.24)Guest time of the process (time spent running a virtual CPU for a guest operating system), measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).- (44)
cguest_time%ld (since Linux 2.6.24)Guest time of the process's children, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).- (45)
start_data%lu (since Linux 3.3) [PT]Address above which program initialized and uninitialized (BSS) data are placed.
- (46)
end_data%lu (since Linux 3.3) [PT]Address below which program initialized and uninitialized (BSS) data are placed.
- (47)
start_brk%lu (since Linux 3.3) [PT]Address above which program heap can be expanded with brk(2).
- (48)
arg_start%lu (since Linux 3.5) [PT]Address above which program command-line arguments (
argv) are placed.- (49)
arg_end%lu (since Linux 3.5) [PT]Address below program command-line arguments (
argv) are placed.- (50)
env_start%lu (since Linux 3.5) [PT]Address above which program environment is placed.
- (51)
env_end%lu (since Linux 3.5) [PT]Address below which program environment is placed.
- (52)
exit_code%d (since Linux 3.5) [PT]The thread's exit status in the form reported by waitpid(2).
/proc/[pid]/statmProvides information about memory usage, measured in pages. The columns are:
size (1) total program size (same as VmSize in/proc/[pid]/status) resident (2) resident set size (same as VmRSS in/proc/[pid]/status) share (3) shared pages (i.e., backed by a file) text (4) text (code) lib (5) library (unused in Linux 2.6) data (6) data + stack dt (7) dirty pages (unused in Linux 2.6)
/proc/[pid]/statusProvides much of the information in /proc/[pid]/stat and /proc/[pid]/statm in a format
that's easier for humans to parse. Here's an
example:
$ cat /proc/$$/status Name: bash Umask: 0022 State: S (sleeping) Tgid: 17248 Ngid: 0 Pid: 17248 PPid: 17200 TracerPid: 0 Uid: 1000 1000 1000 1000 Gid: 100 100 100 100 FDSize: 256 Groups: 16 33 100 NStgid: 17248 NSpid: 17248 NSpgid: 17248 NSsid: 17200 VmPeak: 9136 kB VmSize: 7896 kB VmLck: 0 kB VmPin: 0 kB VmHWM: 7572 kB VmRSS: 6316 kB VmData: 5224 kB VmStk: 88 kB VmExe: 572 kB VmLib: 1708 kB VmPMD: 4 kB VmPTE: 20 kB VmSwap: 0 kB Threads: 1 SigQ: 0/3067 SigPnd: 0000000000000000 ShdPnd: 0000000000000000 SigBlk: 0000000000010000 SigIgn: 0000000000384004 SigCgt: 000000004b813efb CapInh: 0000000000000000 CapPrm: 0000000000000000 CapEff: 0000000000000000 CapBnd: ffffffffffffffff CapAmb: 0000000000000000 Seccomp: 0 Cpus_allowed: 00000001 Cpus_allowed_list: 0 Mems_allowed: 1 Mems_allowed_list: 0 voluntary_ctxt_switches: 150 nonvoluntary_ctxt_switches: 545
The fields are as follows:
Name: Command run by this process.
Umask: Process umask, expressed in octal with a leading zero. (Since Linux 4.7.)
State: Current state of the process. One of "R (running)", "S (sleeping)", "D (disk sleep)", "T (stopped)", "T (tracing stop)", "Z (zombie)", or "X (dead)".
Tgid: Thread group ID (i.e., Process ID).
Ngid: NUMA group ID (0 if none; since Linux 3.13).
Pid: Thread ID (see gettid(2)).
PPid: PID of parent process.
TracerPid: PID of process tracing this process (0 if not being traced).
Uid,Gid: Real, effective, saved set, and filesystem UIDs (GIDs).
FDSize: Number of file descriptor slots currently allocated.
Groups: Supplementary group list.
NStgidThread group ID (i.e., PID) in each of the PID namespaces of which[pid]is a member. The leftmost entry shows the value with respect to the PID namespace of the reading process, followed by the value in successively nested inner namespaces. (Since Linux 4.1.)
NSpidThread ID in each of the PID namespaces of which[pid]is a member. The fields are ordered as forNStgid. (Since Linux 4.1.)
NSpgidProcess group ID in each of the PID namespaces of which[pid]is a member. The fields are ordered as forNStgid. (Since Linux 4.1.)
NSsiddescendant namespace session ID hierarchy Session ID in each of the PID namespaces of which[pid]is a member. The fields are ordered as forNStgid. (Since Linux 4.1.)
VmPeak: Peak virtual memory size.
VmSize: Virtual memory size.
VmLck: Locked memory size (see mlock(3)).
VmPin: Pinned memory size (since Linux 3.2). These are pages that can't be moved because something needs to directly access physical memory.
VmHWM: Peak resident set size ("high water mark").
VmRSS: Resident set size.
VmData,VmStk,VmExe: Size of data, stack, and text segments.
VmLib: Shared library code size.
VmPTE: Page table entries size (since Linux 2.6.10).
VmPMD: Size of second-level page tables (since Linux 4.0).
VmSwap: Swapped-out virtual memory size by anonymous private pages; shmem swap usage is not included (since Linux 2.6.34).
Threads: Number of threads in process containing this thread.
SigQ: This field contains two slash-separated numbers that relate to queued signals for the real user ID of this process. The first of these is the number of currently queued signals for this real user ID, and the second is the resource limit on the number of queued signals for this process (see the description ofRLIMIT_SIGPENDINGin getrlimit(2)).
SigPnd,ShdPnd: Number of signals pending for thread and for process as a whole (see pthreads(7) and signal(7)).
SigBlk,SigIgn,SigCgt: Masks indicating signals being blocked, ignored, and caught (see signal(7)).
CapInh,CapPrm,CapEff: Masks of capabilities enabled in inheritable, permitted, and effective sets (see capabilities(7)).
CapBnd: Capability Bounding set (since Linux 2.6.26, see capabilities(7)).
CapAmb: Ambient capability set (since Linux 4.3, see capabilities(7)).
Seccomp: Seccomp mode of the process (since Linux 3.8, see seccomp(2)). 0 meansSECCOMP_MODE_DISABLED; 1 meansSECCOMP_MODE_STRICT; 2 meansSECCOMP_MODE_FILTER. This field is provided only if the kernel was built with theCONFIG_SECCOMPkernel configuration option enabled.
Cpus_allowed: Mask of CPUs on which this process may run (since Linux 2.6.24, see cpuset(7)).
Cpus_allowed_list: Same as previous, but in "list format" (since Linux 2.6.26, see cpuset(7)).
Mems_allowed: Mask of memory nodes allowed to this process (since Linux 2.6.24, see cpuset(7)).
Mems_allowed_list: Same as previous, but in "list format" (since Linux 2.6.26, see cpuset(7)).
voluntary_ctxt_switches,nonvoluntary_ctxt_switches: Number of voluntary and involuntary context switches (since Linux 2.6.23).
/proc/[pid]/syscall (since Linux
2.6.27)This file exposes the system call number and argument registers for the system call currently being executed by the process, followed by the values of the stack pointer and program counter registers. The values of all six argument registers are exposed, although most system calls use fewer registers.
If the process is blocked, but not in a system call, then the file displays −1 in place of the system call number, followed by just the values of the stack pointer and program counter. If process is not blocked, then the file contains just the string "running".
This file is present only if the kernel was
configured with CONFIG_HAVE_ARCH_TRACEHOOK.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check;
see ptrace(2).
/proc/[pid]/task (since Linux
2.6.0-test6)This is a directory that contains one subdirectory
for each thread in the process. The name of each
subdirectory is the numerical thread ID ([tid]) of the thread
(see gettid(2)). Within
each of these subdirectories, there is a set of files
with the same names and contents as under the
/proc/[pid]
directories. For attributes that are shared by all
threads, the contents for each of the files under the
task/[tid]
subdirectories will be the same as in the
corresponding file in the parent /proc/[pid] directory (e.g., in a
multithreaded process, all of the task/[tid]/cwd files
will have the same value as the /proc/[pid]/cwd file in the parent
directory, since all of the threads in a process
share a working directory). For attributes that are
distinct for each thread, the corresponding files
under task/[tid] may have
different values (e.g., various fields in each of the
task/[tid]/status
files may be different for each thread).
In a multithreaded process, the contents of the
/proc/[pid]/task
directory are not available if the main thread has
already terminated (typically by calling pthread_exit(3)).
/proc/[pid]/timers (since Linux
3.10)A list of the POSIX timers for this process. Each timer is listed with a line that starts with the string "ID:". For example:
ID: 1 signal: 60/00007fff86e452a8 notify: signal/pid.2634 ClockID: 0 ID: 0 signal: 60/00007fff86e452a8 notify: signal/pid.2634 ClockID: 1
The lines shown for each timer have the following meanings:
IDThe ID for this timer. This is not the same as the timer ID returned by timer_create(2); rather, it is the same kernel-internal ID that is available via the
si_timeridfield of thesiginfo_tstructure (see sigaction(2)).signalThis is the signal number that this timer uses to deliver notifications followed by a slash, and then the
sigev_valuevalue supplied to the signal handler. Valid only for timers that notify via a signal.notifyThe part before the slash specifies the mechanism that this timer uses to deliver notifications, and is one of "thread", "signal", or "none". Immediately following the slash is either the string "tid" for timers with
SIGEV_THREAD_IDnotification, or "pid" for timers that notify by other mechanisms. Following the "." is the PID of the process (or the kernel thread ID of the thread) that will be delivered a signal if the timer delivers notifications via a signal.ClockIDThis field identifies the clock that the timer uses for measuring time. For most clocks, this is a number that matches one of the user-space
CLOCK_*constants exposed via<time.h>CLOCK_PROCESS_CPUTIME_IDtimers display with a value of -6 in this field.CLOCK_THREAD_CPUTIME_IDtimers display with a value of -2 in this field.
This file is available only when the kernel was
configured with CONFIG_CHECKPOINT_RESTORE.
/proc/[pid]/timerslack_ns (since
Linux 4.6)This file exposes the process's "current" timer
slack value, expressed in nanoseconds. The file is
writable, allowing the process's timer slack value to
be changed. Writing 0 to this file resets the
"current" timer slack to the "default" timer slack
value. For further details, see the discussion of
PR_SET_TIMERSLACK in
prctl(2).
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check;
see ptrace(2).
/proc/[pid]/uid_map,
/proc/[pid]/gid_map (since Linux
3.5)See user_namespaces(7).
/proc/[pid]/wchan (since Linux
2.6.0)The symbolic name corresponding to the location in the kernel where the process is sleeping.
Permission to access this file is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS check; see
ptrace(2).
/proc/apmAdvanced power management version and battery
information when CONFIG_APM is defined at kernel
compilation time.
/proc/buddyinfoThis file contains information which is used for diagnosing memory fragmentation issues. Each line starts with the identification of the node and the name of the zone which together identify a memory region This is then followed by the count of available chunks of a certain order in which these zones are split. The size in bytes of a certain order is given by the formula:
(2^order) * PAGE_SIZE
The binary buddy allocator algorithm inside the kernel will split one chunk into two chunks of a smaller order (thus with half the size) or combine two contiguous chunks into one larger chunk of a higher order (thus with double the size) to satisfy allocation requests and to counter memory fragmentation. The order matches the column number, when starting to count at zero.
For example on a x86_64 system:
Node 0, zone DMA 1 1 1 0 2 1 1 0 1 1 3 Node 0, zone DMA32 65 47 4 81 52 28 13 10 5 1 404 Node 0, zone Normal 216 55 189 101 84 38 37 27 5 3 587
In this example, there is one node containing
three zones and there are 11 different chunk sizes.
If the page size is 4 kilobytes, then the first zone
called DMA (on x86 the
first 16 megabyte of memory) has 1 chunk of 4
kilobytes (order 0) available and has 3 chunks of 4
megabytes (order 10) available.
If the memory is heavily fragmented, the counters for higher order chunks will be zero and allocation of large contiguous areas will fail.
Further information about the zones can be found
in /proc/zoneinfo.
/proc/busContains subdirectories for installed busses.
/proc/bus/pccardSubdirectory for PCMCIA devices when CONFIG_PCMCIA is set at kernel
compilation time.
/proc/bus/pccard/drivers/proc/bus/pciContains various bus subdirectories and pseudo-files containing information about PCI busses, installed devices, and device drivers. Some of these files are not ASCII.
/proc/bus/pci/devicesInformation about PCI devices. They may be accessed through lspci(8) and setpci(8).
/proc/cgroups (since Linux
2.6.24)See cgroups(7).
/proc/cmdlineArguments passed to the Linux kernel at boot time. Often done via a boot manager such as lilo(8) or grub(8).
/proc/config.gz (since Linux
2.6)This file exposes the configuration options that
were used to build the currently running kernel, in
the same format as they would be shown in the
.config
file that resulted when configuring the kernel (using
make xconfig,
make config,
or similar). The file contents are compressed; view
or search them using zcat(1) and
zgrep(1). As long as no
changes have been made to the following file, the
contents of /proc/config.gz are the same as
those provided by :
cat /lib/modules/$(uname −r)/build/.config
/proc/config.gz is
provided only if the kernel is configured with
CONFIG_IKCONFIG_PROC.
/proc/cryptoA list of the ciphers provided by the kernel
crypto API. For details, see the kernel Linux Kernel Crypto API
documentation available under the kernel source
directory Documentation/DocBook. (That
documentation can be built using a command such as
make htmldocs
in the root directory of the kernel source tree.)
/proc/cpuinfoThis is a collection of CPU and system
architecture dependent items, for each supported
architecture a different list. Two common entries are
processor which gives
CPU number and bogomips;
a system constant that is calculated during kernel
initialization. SMP machines have information for
each CPU. The lscpu(1) command
gathers its information from this file.
/proc/devicesText listing of major numbers and device groups. This can be used by MAKEDEV scripts for consistency with the kernel.
/proc/diskstats (since Linux
2.5.69)This file contains disk I/O statistics for each
disk device. See the Linux kernel source file
Documentation/iostats.txt for
further information.
/proc/dmaThis is a list of the registered ISA DMA (direct memory access)
channels in use.
/proc/driverEmpty subdirectory.
/proc/execdomainsList of the execution domains (ABI personalities).
/proc/fbFrame buffer information when CONFIG_FB is defined during kernel
compilation.
/proc/filesystemsA text listing of the filesystems which are supported by the kernel, namely filesystems which were compiled into the kernel or whose kernel modules are currently loaded. (See also filesystems(5).) If a filesystem is marked with "nodev", this means that it does not require a block device to be mounted (e.g., virtual filesystem, network filesystem).
Incidentally, this file may be used by mount(8) when no filesystem is specified and it didn't manage to determine the filesystem type. Then filesystems contained in this file are tried (excepted those that are marked with "nodev").
/proc/fsContains subdirectories that in turn contain files with information about (certain) mounted filesystems.
/proc/ideThis directory exists on systems with the IDE bus. There are directories for each IDE channel and attached device. Files include:
cache buffer size in KB capacity number of sectors driver driver version geometry physical and logical geometry identify in hexadecimal media media type model manufacturer's model number settings drive settings smart_thresholds in hexadecimal smart_values in hexadecimal
The hdparm(8) utility provides access to this information in a friendly format.
/proc/interruptsThis is used to record the number of interrupts per CPU per IO device. Since Linux 2.6.24, for the i386 and x86_64 architectures, at least, this also includes interrupts internal to the system (that is, not associated with a device as such), such as NMI (nonmaskable interrupt), LOC (local timer interrupt), and for SMP systems, TLB (TLB flush interrupt), RES (rescheduling interrupt), CAL (remote function call interrupt), and possibly others. Very easy to read formatting, done in ASCII.
/proc/iomemI/O memory map in Linux 2.4.
/proc/ioportsThis is a list of currently registered Input-Output port regions that are in use.
/proc/kallsyms (since Linux
2.5.71)This holds the kernel exported symbol definitions
used by the modules(X)
tools to dynamically link and bind loadable modules.
In Linux 2.5.47 and earlier, a similar file with
slightly different syntax was named ksyms.
/proc/kcoreThis file represents the physical memory of the
system and is stored in the ELF core file format.
With this pseudo-file, and an unstripped kernel
(/usr/src/linux/vmlinux) binary, GDB
can be used to examine the current state of any
kernel data structures.
The total length of the file is the size of physical memory (RAM) plus 4KB.
/proc/kmsgThis file can be used instead of the syslog(2) system call to read kernel messages. A process must have superuser privileges to read this file, and only one process should read this file. This file should not be read if a syslog process is running which uses the syslog(2) system call facility to log kernel messages.
Information in this file is retrieved with the dmesg(1) program.
/proc/kpagecount (since Linux
2.6.25)This file contains a 64-bit count of the number of
times each physical page frame is mapped, indexed by
page frame number (see the discussion of /proc/[pid]/pagemap).
The /proc/kpagecount
file is present only if the CONFIG_PROC_PAGE_MONITOR kernel
configuration option is enabled.
/proc/kpageflags (since Linux
2.6.25)This file contains 64-bit masks corresponding to
each physical page frame; it is indexed by page frame
number (see the discussion of /proc/[pid]/pagemap). The bits are
as follows:
0 - KPF_LOCKED 1 - KPF_ERROR 2 - KPF_REFERENCED 3 - KPF_UPTODATE 4 - KPF_DIRTY 5 - KPF_LRU 6 - KPF_ACTIVE 7 - KPF_SLAB 8 - KPF_WRITEBACK 9 - KPF_RECLAIM 10 - KPF_BUDDY 11 - KPF_MMAP (since Linux 2.6.31) 12 - KPF_ANON (since Linux 2.6.31) 13 - KPF_SWAPCACHE (since Linux 2.6.31) 14 - KPF_SWAPBACKED (since Linux 2.6.31) 15 - KPF_COMPOUND_HEAD (since Linux 2.6.31) 16 - KPF_COMPOUND_TAIL (since Linux 2.6.31) 16 - KPF_HUGE (since Linux 2.6.31) 18 - KPF_UNEVICTABLE (since Linux 2.6.31) 19 - KPF_HWPOISON (since Linux 2.6.31) 20 - KPF_NOPAGE (since Linux 2.6.31) 21 - KPF_KSM (since Linux 2.6.32) 22 - KPF_THP (since Linux 3.4)
For further details on the meanings of these bits,
see the kernel source file Documentation/vm/pagemap.txt.
Before kernel 2.6.29, KPF_WRITEBACK, KPF_RECLAIM, KPF_BUDDY, and KPF_LOCKED did not report
correctly.
The /proc/kpageflags
file is present only if the CONFIG_PROC_PAGE_MONITOR kernel
configuration option is enabled.
/proc/ksyms (Linux
1.1.23-2.5.47)See /proc/kallsyms.
/proc/loadavgThe first three fields in this file are load average figures giving the number of jobs in the run queue (state R) or waiting for disk I/O (state D) averaged over 1, 5, and 15 minutes. They are the same as the load average numbers given by uptime(1) and other programs. The fourth field consists of two numbers separated by a slash (/). The first of these is the number of currently runnable kernel scheduling entities (processes, threads). The value after the slash is the number of kernel scheduling entities that currently exist on the system. The fifth field is the PID of the process that was most recently created on the system.
/proc/locksThis file shows current file locks (flock(2) and fcntl(2)) and leases (fcntl(2)).
/proc/malloc (only up to and including Linux
2.2)This file is present only if CONFIG_DEBUG_MALLOC was defined
during compilation.
/proc/meminfoThis file reports statistics about memory usage on the system. It is used by free(1) to report the amount of free and used memory (both physical and swap) on the system as well as the shared memory and buffers used by the kernel. Each line of the file consists of a parameter name, followed by a colon, the value of the parameter, and an option unit of measurement (e.g., "kB"). The list below describes the parameter names and the format specifier required to read the field value. Except as noted below, all of the fields have been present since at least Linux 2.6.0. Some fields are displayed only if the kernel was configured with various options; those dependencies are noted in the list.
MemTotal%luTotal usable RAM (i.e., physical RAM minus a few reserved bits and the kernel binary code).
MemFree%luThe sum of
LowFree+HighFree.MemAvailable%lu (since Linux 3.14)An estimate of how much memory is available for starting new applications, without swapping.
Buffers%luRelatively temporary storage for raw disk blocks that shouldn't get tremendously large (20MB or so).
Cached%luIn-memory cache for files read from the disk (the page cache). Doesn't include
SwapCached.SwapCached%luMemory that once was swapped out, is swapped back in but still also is in the swap file. (If memory pressure is high, these pages don't need to be swapped out again because they are already in the swap file. This saves I/O.)
Active%luMemory that has been used more recently and usually not reclaimed unless absolutely necessary.
Inactive%luMemory which has been less recently used. It is more eligible to be reclaimed for other purposes.
Active(anon)%lu (since Linux 2.6.28)[To be documented.]
Inactive(anon)%lu (since Linux 2.6.28)[To be documented.]
Active(file)%lu (since Linux 2.6.28)[To be documented.]
Inactive(file)%lu (since Linux 2.6.28)[To be documented.]
Unevictable%lu (since Linux 2.6.28)(From Linux 2.6.28 to 2.6.30,
CONFIG_UNEVICTABLE_LRUwas required.) [To be documented.]Mlocked%lu (since Linux 2.6.28)(From Linux 2.6.28 to 2.6.30,
CONFIG_UNEVICTABLE_LRUwas required.) [To be documented.]HighTotal%lu(Starting with Linux 2.6.19,
CONFIG_HIGHMEMis required.) Total amount of highmem. Highmem is all memory above ~860MB of physical memory. Highmem areas are for use by user-space programs, or for the page cache. The kernel must use tricks to access this memory, making it slower to access than lowmem.HighFree%lu(Starting with Linux 2.6.19,
CONFIG_HIGHMEMis required.) Amount of free highmem.LowTotal%lu(Starting with Linux 2.6.19,
CONFIG_HIGHMEMis required.) Total amount of lowmem. Lowmem is memory which can be used for everything that highmem can be used for, but it is also available for the kernel's use for its own data structures. Among many other things, it is where everything fromSlabis allocated. Bad things happen when you're out of lowmem.LowFree%lu(Starting with Linux 2.6.19,
CONFIG_HIGHMEMis required.) Amount of free lowmem.MmapCopy%lu (since Linux 2.6.29)(
CONFIG_MMUis required.) [To be documented.]SwapTotal%luTotal amount of swap space available.
SwapFree%luAmount of swap space that is currently unused.
Dirty%luMemory which is waiting to get written back to the disk.
Writeback%luMemory which is actively being written back to the disk.
AnonPages%lu (since Linux 2.6.18)Non-file backed pages mapped into user-space page tables.
Mapped%luFiles which have been mapped into memory (with mmap(2)), such as libraries.
Shmem%lu (since Linux 2.6.32)[To be documented.]
Slab%luIn-kernel data structures cache.
SReclaimable%lu (since Linux 2.6.19)Part of
Slab, that might be reclaimed, such as caches.SUnreclaim%lu (since Linux 2.6.19)Part of
Slab, that cannot be reclaimed on memory pressure.KernelStack%lu (since Linux 2.6.32)Amount of memory allocated to kernel stacks.
PageTables%lu (since Linux 2.6.18)Amount of memory dedicated to the lowest level of page tables.
Quicklists%lu (since Linux 2.6.27)(
CONFIG_QUICKLISTis required.) [To be documented.]NFS_Unstable%lu (since Linux 2.6.18)NFS pages sent to the server, but not yet committed to stable storage.
Bounce%lu (since Linux 2.6.18)Memory used for block device "bounce buffers".
WritebackTmp%lu (since Linux 2.6.26)Memory used by FUSE for temporary writeback buffers.
CommitLimit%lu (since Linux 2.6.10)This is the total amount of memory currently available to be allocated on the system, expressed in kilobytes. This limit is adhered to only if strict overcommit accounting is enabled (mode 2 in
/proc/sys/vm/overcommit_memory). The limit is calculated according to the formula described under/proc/sys/vm/overcommit_memory. For further details, see the kernel source fileDocumentation/vm/overcommit-accounting.Committed_AS%luThe amount of memory presently allocated on the system. The committed memory is a sum of all of the memory which has been allocated by processes, even if it has not been "used" by them as of yet. A process which allocates 1GB of memory (using malloc(3) or similar), but touches only 300MB of that memory will show up as using only 300MB of memory even if it has the address space allocated for the entire 1GB.
This 1GB is memory which has been "committed" to by the VM and can be used at any time by the allocating application. With strict overcommit enabled on the system (mode 2 in
/proc/sys/vm/overcommit_memory), allocations which would exceed theCommitLimitwill not be permitted. This is useful if one needs to guarantee that processes will not fail due to lack of memory once that memory has been successfully allocated.VmallocTotal%luTotal size of vmalloc memory area.
VmallocUsed%luAmount of vmalloc area which is used.
VmallocChunk%luLargest contiguous block of vmalloc area which is free.
HardwareCorrupted%lu (since Linux 2.6.32)(
CONFIG_MEMORY_FAILUREis required.) [To be documented.]AnonHugePages%lu (since Linux 2.6.38)(
CONFIG_TRANSPARENT_HUGEPAGEis required.) Non-file backed huge pages mapped into user-space page tables.CmaTotal%lu (since Linux 3.1)Total CMA (Contiguous Memory Allocator) pages. (
CONFIG_CMAis required.)CmaFree%lu (since Linux 3.1)Free CMA (Contiguous Memory Allocator) pages. (
CONFIG_CMAis required.)HugePages_Total%lu(
CONFIG_HUGETLB_PAGEis required.) The size of the pool of huge pages.HugePages_Free%lu(
CONFIG_HUGETLB_PAGEis required.) The number of huge pages in the pool that are not yet allocated.HugePages_Rsvd%lu (since Linux 2.6.17)(
CONFIG_HUGETLB_PAGEis required.) This is the number of huge pages for which a commitment to allocate from the pool has been made, but no allocation has yet been made. These reserved huge pages guarantee that an application will be able to allocate a huge page from the pool of huge pages at fault time.HugePages_Surp%lu (since Linux 2.6.24)(
CONFIG_HUGETLB_PAGEis required.) This is the number of huge pages in the pool above the value in/proc/sys/vm/nr_hugepages. The maximum number of surplus huge pages is controlled by/proc/sys/vm/nr_overcommit_hugepages.Hugepagesize%lu(
CONFIG_HUGETLB_PAGEis required.) The size of huge pages.DirectMap4k%lu (since Linux 2.6.27)Number of bytes of RAM linearly mapped by kernel in 4kB pages. (x86.)
DirectMap4M%lu (since Linux 2.6.27)Number of bytes of RAM linearly mapped by kernel in 4MB pages. (x86 with
CONFIG_X86_64orCONFIG_X86_PAEenabled.)DirectMap2M%lu (since Linux 2.6.27)Number of bytes of RAM linearly mapped by kernel in 2MB pages. (x86 with neither
CONFIG_X86_64norCONFIG_X86_PAEenabled.)DirectMap1G%lu (since Linux 2.6.27)(x86 with
CONFIG_X86_64andCONFIG_X86_DIRECT_GBPAGESenabled.)
/proc/modulesA text list of the modules that have been loaded by the system. See also lsmod(8).
/proc/mountsBefore kernel 2.4.19, this file was a list of all
the filesystems currently mounted on the system. With
the introduction of per-process mount namespaces in
Linux 2.4.19 (see mount_namespaces(7)),
this file became a link to /proc/self/mounts, which lists the
mount points of the process's own mount namespace.
The format of this file is documented in fstab(5).
/proc/mtrrMemory Type Range Registers. See the Linux kernel
source file Documentation/mtrr.txt for
details.
/proc/netThis directory contains various files and subdirectories containing information about the networking layer. The files contain ASCII structures and are, therefore, readable with cat(1). However, the standard netstat(8) suite provides much cleaner access to these files.
With the advent of network namespaces, various
information relating to the network stack is
virtualized (see namespaces(7)).
Thus, since Linux 2.6.25, /proc/net is a symbolic link to the
directory /proc/self/net, which contains the
same files and directories as listed below. However,
these files and directories now expose information
for the network namespace of which the process is a
member.
/proc/net/arpThis holds an ASCII readable dump of the kernel ARP table used for address resolutions. It will show both dynamically learned and preprogrammed ARP entries. The format is:
IP addressHW typeFlagsHW addressMaskDevice192.168.0.500x10x200:50:BF:25:68:F3*eth0192.168.0.2500x10xc00:00:00:00:00:00*eth0
Here "IP address" is the IPv4 address of the
machine and the "HW type" is the hardware type of the
address from RFC 826. The flags are the internal
flags of the ARP structure (as defined in
/usr/include/linux/if_arp.h)
and the "HW address" is the data link layer mapping
for that IP address if it is known.
/proc/net/devThe dev pseudo-file contains network device status information. This gives the number of received and sent packets, the number of errors and collisions and other basic statistics. These are used by the ifconfig(8) program to report device status. The format is:
InterfaceReceiveTransmitbytespacketserrsdropfifoframecompressedmulticastbytespacketserrsdropfifocollscarriercompressedlo:277677011307000000277677011307000000eth0:121564527510000001782404432400042700ppp0:162227055521000003541305669000000tap0:771481000000771481000000
/proc/net/dev_mcastDefined in /usr/src/linux/net/core/dev_mcast.c:
indxinterface_namedmi_udmi_gdmi_address2eth01001005e0000013eth11001005e0000014eth21001005e000001
/proc/net/igmpInternet Group Management Protocol. Defined in
/usr/src/linux/net/core/igmp.c.
/proc/net/rarpThis file uses the same format as the arp file and contains the current
reverse mapping database used to provide rarp(8) reverse address
lookup services. If RARP is not configured into the
kernel, this file will not be present.
/proc/net/rawHolds a dump of the RAW socket table. Much of the information is not of use apart from debugging. The "sl" value is the kernel hash slot for the socket, the "local_address" is the local address and protocol number pair. "St" is the internal status of the socket. The "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of kernel memory usage. The "tr", "tm−>when", and "rexmits" fields are not used by RAW. The "uid" field holds the effective UID of the creator of the socket.
/proc/net/snmpThis file holds the ASCII data needed for the IP, ICMP, TCP, and UDP management information bases for an SNMP agent.
/proc/net/tcpHolds a dump of the TCP socket table. Much of the information is not of use apart from debugging. The "sl" value is the kernel hash slot for the socket, the "local_address" is the local address and port number pair. The "rem_address" is the remote address and port number pair (if connected). "St" is the internal status of the socket. The "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of kernel memory usage. The "tr", "tm−>when", and "rexmits" fields hold internal information of the kernel socket state and are useful only for debugging. The "uid" field holds the effective UID of the creator of the socket.
/proc/net/udpHolds a dump of the UDP socket table. Much of the information is not of use apart from debugging. The "sl" value is the kernel hash slot for the socket, the "local_address" is the local address and port number pair. The "rem_address" is the remote address and port number pair (if connected). "St" is the internal status of the socket. The "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of kernel memory usage. The "tr", "tm−>when", and "rexmits" fields are not used by UDP. The "uid" field holds the effective UID of the creator of the socket. The format is:
sllocal_addressrem_addresssttx_queue rx_queuetr rexmitstm−>whenuid1:01642C89:02010C642C89:03FF0100000000:0000000101:000071BA0000000001:00000000:080100000000:00000A00000000:0000000000:000000006F00010001:00000000:020100000000:00000A00000000:0000000000:00000000000000000
/proc/net/unixLists the UNIX domain sockets present within the system and their status. The format is:
Num |
RefCount |
Protocol |
Flags |
Type |
St |
Path |
0: |
00000002 |
00000000 |
00000000 |
0001 |
03 |
|
1: |
00000001 |
00000000 |
00010000 |
0001 |
01 |
/dev/printer |
The fields are as follows:
Num:the kernel table slot number.
RefCount:the number of users of the socket.
Protocol:currently always 0.
Flags:the internal kernel flags holding the status of the socket.
Type:the socket type. For
SOCK_STREAMsockets, this is 0001; forSOCK_DGRAMsockets, it is 0002; and forSOCK_SEQPACKETsockets, it is 0005.St:the internal state of the socket.
Path:the bound path (if any) of the socket. Sockets in the abstract namespace are included in the list, and are shown with a
Paththat commences with the character '@'.
/proc/net/netfilter/nfnetlink_queueThis file contains information about netfilter userspace queueing, if used. Each line represents a queue. Queues that have not been subscribed to by userspace are not shown.
1 4207 0 2 65535 0 0 0 1 (1) (2) (3)(4) (5) (6) (7) (8)
The fields in each line are:
- (1)
The ID of the queue. This matches what is specified in the
−−queue−numor−−queue−balanceoptions to the iptables(8) NFQUEUE target. See iptables-extensions(8) for more information.- (2)
The netlink port ID subscribed to the queue.
- (3)
The number of packets currently queued and waiting to be processed by the application.
- (4)
The copy mode of the queue. It is either 1 (metadata only) or 2 (also copy payload data to userspace).
- (5)
Copy range; that is, how many bytes of packet payload should be copied to userspace at most.
- (6)
queue dropped. Number of packets that had to be dropped by the kernel because too many packets are already waiting for userspace to send back the mandatory accept/drop verdicts.
- (7)
queue user dropped. Number of packets that were dropped within the netlink subsystem. Such drops usually happen when the corresponding socket buffer is full; that is, userspace is not able to read messages fast enough.
- (8)
sequence number. Every queued packet is associated with a (32-bit) monotonically-increasing sequence number. This shows the ID of the most recent packet queued.
The last number exists only for compatibility reasons and is always 1.
/proc/partitionsContains the major and minor numbers of each partition as well as the number of 1024-byte blocks and the partition name.
/proc/pciThis is a listing of all PCI devices found during kernel initialization and their configuration.
This file has been deprecated in favor of a new
/proc interface for PCI
(/proc/bus/pci). It
became optional in Linux 2.2 (available with
CONFIG_PCI_OLD_PROC set
at kernel compilation). It became once more
nonoptionally enabled in Linux 2.4. Next, it was
deprecated in Linux 2.6 (still available with
CONFIG_PCI_LEGACY_PROC
set), and finally removed altogether since Linux
2.6.17.
/proc/profile (since Linux
2.4)This file is present only if the kernel was booted
with the profile=1
command-line option. It exposes kernel profiling
information in a binary format for use by
readprofile(1). Writing
(e.g., an empty string) to this file resets the
profiling counters; on some architectures, writing a
binary integer "profiling multiplier" of size
sizeof(int)
sets the profiling interrupt frequency.
/proc/scsiA directory with the scsi mid-level pseudo-file and
various SCSI low-level driver directories, which
contain a file for each SCSI host in this system, all
of which give the status of some part of the SCSI IO
subsystem. These files contain ASCII structures and
are, therefore, readable with cat(1).
You can also write to some of the files to reconfigure the subsystem or switch certain features on or off.
/proc/scsi/scsiThis is a listing of all SCSI devices known to the
kernel. The listing is similar to the one seen during
bootup. scsi currently supports only the add-single-device
command which allows root to add a hotplugged device
to the list of known devices.
The command
echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi
will cause host scsi1 to scan on SCSI channel 0 for a device on ID 5 LUN 0. If there is already a device known on this address or the address is invalid, an error will be returned.
/proc/scsi/[drivername][drivername] can
currently be NCR53c7xx, aha152x, aha1542, aha1740,
aic7xxx, buslogic, eata_dma, eata_pio, fdomain,
in2000, pas16, qlogic, scsi_debug, seagate, t128,
u15-24f, ultrastore, or wd7000. These directories
show up for all drivers that registered at least one
SCSI HBA. Every directory contains one file per
registered host. Every host-file is named after the
number the host was assigned during
initialization.
Reading these files will usually show driver and host configuration, statistics, and so on.
Writing to these files allows different things on
different hosts. For example, with the latency and nolatency commands, root can switch
on and off command latency measurement code in the
eata_dma driver. With the lockup and unlock commands, root can control
bus lockups simulated by the scsi_debug driver.
/proc/selfThis directory refers to the process accessing the
/proc filesystem, and
is identical to the /proc directory named by the
process ID of the same process.
/proc/slabinfoInformation about kernel caches. Since Linux
2.6.16 this file is present only if the CONFIG_SLAB kernel configuration
option is enabled. The columns in /proc/slabinfo are:
cache-name num-active-objs total-objs object-size num-active-slabs total-slabs num-pages-per-slab
See slabinfo(5) for details.
/proc/statkernel/system statistics. Varies with architecture. Common entries include:
- cpu 3357 0 4313 1362393
The amount of time, measured in units of USER_HZ (1/100ths of a second on most architectures, use
sysconf(_SC_CLK_TCK)to obtain the right value), that the system spent in various states:
user(1) Time spent in user mode.
nice(2) Time spent in user mode with low priority (nice).
system(3) Time spent in system mode.
idle(4) Time spent in the idle task. This value should be USER_HZ times the second entry in the
/proc/uptimepseudo-file.iowait(since Linux 2.5.41)(5) Time waiting for I/O to complete.
irq(since Linux 2.6.0-test4)(6) Time servicing interrupts.
softirq(since Linux 2.6.0-test4)(7) Time servicing softirqs.
steal(since Linux 2.6.11)(8) Stolen time, which is the time spent in other operating systems when running in a virtualized environment
guest(since Linux 2.6.24)(9) Time spent running a virtual CPU for guest operating systems under the control of the Linux kernel.
guest_nice(since Linux 2.6.33)(10) Time spent running a niced guest (virtual CPU for guest operating systems under the control of the Linux kernel).
- page 5741 1808
The number of pages the system paged in and the number that were paged out (from disk).
- swap 1 0
The number of swap pages that have been brought in and out.
- intr 1462898
This line shows counts of interrupts serviced since boot time, for each of the possible system interrupts. The first column is the total of all interrupts serviced including unnumbered architecture specific interrupts; each subsequent column is the total for that particular numbered interrupt. Unnumbered interrupts are not shown, only summed into the total.
- disk_io: (2,0):(31,30,5764,1,2) (3,0):...
(major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written)
(Linux 2.4 only)
- ctxt 115315
The number of context switches that the system underwent.
- btime 769041601
boot time, in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
- processes 86031
Number of forks since boot.
- procs_running 6
Number of processes in runnable state. (Linux 2.5.45 onward.)
- procs_blocked 2
Number of processes blocked waiting for I/O to complete. (Linux 2.5.45 onward.)
/proc/swapsSwap areas in use. See also swapon(8).
/proc/sysThis directory (present since 1.3.57) contains a
number of files and subdirectories corresponding to
kernel variables. These variables can be read and
sometimes modified using the /proc filesystem, and the
(deprecated) sysctl(2) system
call.
String values may be terminated by either '\0' or '\n'.
Integer and long values may be written either in decimal or in hexadecimal notation (e.g. 0x3FFF). When writing multiple integer or long values, these may be separated by any of the following whitespace characters: ' ', '\t', or '\n'. Using other separators leads to the error EINVAL.
/proc/sys/abi (since Linux
2.4.10)This directory may contain files with application
binary information. See the Linux kernel source file
Documentation/sysctl/abi.txt for
more information.
/proc/sys/debugThis directory may be empty.
/proc/sys/devThis directory contains device-specific
information (e.g., dev/cdrom/info). On some systems, it
may be empty.
/proc/sys/fsThis directory contains the files and subdirectories for kernel variables related to filesystems.
/proc/sys/fs/binfmt_miscDocumentation for files in this directory can be
found in the Linux kernel sources in Documentation/binfmt_misc.txt.
/proc/sys/fs/dentry-state (since
Linux 2.2)This file contains information about the status of
the directory cache (dcache). The file contains six
numbers, nr_dentry,
nr_unused, age_limit (age in seconds),
want_pages (pages
requested by system) and two dummy values.
nr_dentryis the number of allocated dentries (dcache entries). This field is unused in Linux 2.2.
nr_unusedis the number of unused dentries.
age_limitis the age in seconds after which dcache entries can be reclaimed when memory is short.
want_pagesis nonzero when the kernel has called shrink_dcache_pages() and the dcache isn't pruned yet.
/proc/sys/fs/dir-notify-enableThis file can be used to disable or enable the
dnotify interface
described in fcntl(2) on a
system-wide basis. A value of 0 in this file disables
the interface, and a value of 1 enables it.
/proc/sys/fs/dquot-maxThis file shows the maximum number of cached disk quota entries. On some (2.4) systems, it is not present. If the number of free cached disk quota entries is very low and you have some awesome number of simultaneous system users, you might want to raise the limit.
/proc/sys/fs/dquot-nrThis file shows the number of allocated disk quota entries and the number of free disk quota entries.
/proc/sys/fs/epoll (since Linux
2.6.28)This directory contains the file max_user_watches, which can be used
to limit the amount of kernel memory consumed by the
epoll interface. For
further details, see epoll(7).
/proc/sys/fs/file-maxThis file defines a system-wide limit on the
number of open files for all processes. System calls
that fail when encountering this limit fail with the
error ENFILE. (See
also setrlimit(2), which
can be used by a process to set the per-process
limit, RLIMIT_NOFILE,
on the number of files it may open.) If you get lots
of error messages in the kernel log about running out
of file handles (look for "VFS: file-max limit
<number> reached"), try increasing this
value:
echo 100000 > /proc/sys/fs/file-max
Privileged processes (CAP_SYS_ADMIN) can override the
file-max
limit.
/proc/sys/fs/file-nrThis (read-only) file contains three numbers: the
number of allocated file handles (i.e., the number of
files presently opened); the number of free file
handles; and the maximum number of file handles
(i.e., the same value as /proc/sys/fs/file-max). If the
number of allocated file handles is close to the
maximum, you should consider increasing the maximum.
Before Linux 2.6, the kernel allocated file handles
dynamically, but it didn't free them again. Instead
the free file handles were kept in a list for
reallocation; the "free file handles" value indicates
the size of that list. A large number of free file
handles indicates that there was a past peak in the
usage of open file handles. Since Linux 2.6, the
kernel does deallocate freed file handles, and the
"free file handles" value is always zero.
/proc/sys/fs/inode-max (only present until
Linux 2.2)This file contains the maximum number of in-memory
inodes. This value should be 3-4 times larger than
the value in file-max, since
stdin, stdout and network sockets also need
an inode to handle them. When you regularly run out
of inodes, you need to increase this value.
Starting with Linux 2.4, there is no longer a static limit on the number of inodes, and this file is removed.
/proc/sys/fs/inode-nrThis file contains the first two values from
inode-state.
/proc/sys/fs/inode-stateThis file contains seven numbers: nr_inodes, nr_free_inodes, preshrink, and four dummy values
(always zero).
nr_inodes is the
number of inodes the system has allocated.
nr_free_inodes
represents the number of free inodes.
preshrink is nonzero
when the nr_inodes >
inode-max
and the system needs to prune the inode list instead
of allocating more; since Linux 2.4, this field is a
dummy value (always zero).
/proc/sys/fs/inotify (since Linux
2.6.13)This directory contains files max_queued_events, max_user_instances, and max_user_watches, that can be used
to limit the amount of kernel memory consumed by the
inotify interface. For
further details, see inotify(7).
/proc/sys/fs/lease-break-timeThis file specifies the grace period that the kernel grants to a process holding a file lease (fcntl(2)) after it has sent a signal to that process notifying it that another process is waiting to open the file. If the lease holder does not remove or downgrade the lease within this grace period, the kernel forcibly breaks the lease.
/proc/sys/fs/leases-enableThis file can be used to enable or disable file leases (fcntl(2)) on a system-wide basis. If this file contains the value 0, leases are disabled. A nonzero value enables leases.
/proc/sys/fs/mqueue (since Linux
2.6.6)This directory contains files msg_max, msgsize_max, and queues_max, controlling the
resources used by POSIX message queues. See mq_overview(7) for
details.
/proc/sys/fs/nr_open (since Linux
2.6.25)This file imposes ceiling on the value to which
the RLIMIT_NOFILE
resource limit can be raised (see getrlimit(2)). This
ceiling is enforced for both unprivileged and
privileged process. The default value in this file is
1048576. (Before Linux 2.6.25, the ceiling for
RLIMIT_NOFILE was
hard-coded to the same value.)
/proc/sys/fs/overflowgid and
/proc/sys/fs/overflowuidThese files allow you to change the value of the fixed UID and GID. The default is 65534. Some filesystems support only 16-bit UIDs and GIDs, although in Linux UIDs and GIDs are 32 bits. When one of these filesystems is mounted with writes enabled, any UID or GID that would exceed 65535 is translated to the overflow value before being written to disk.
/proc/sys/fs/pipe-max-size (since
Linux 2.6.35)The value in this file defines an upper limit for
raising the capacity of a pipe using the fcntl(2)
F_SETPIPE_SZ operation.
This limit applies only to unprivileged processes.
The default value for this file is 1,048,576. The
value assigned to this file may be rounded upward, to
reflect the value actually employed for a convenient
implementation. To determine the rounded-up value,
display the contents of this file after assigning a
value to it. The minimum value that can be assigned
to this file is the system page size.
/proc/sys/fs/protected_hardlinks
(since Linux 3.6)When the value in this file is 0, no restrictions are placed on the creation of hard links (i.e., this is the historical behavior before Linux 3.6). When the value in this file is 1, a hard link can be created to a target file only if one of the following conditions is true:
The caller has the
CAP_FOWNERcapability.The filesystem UID of the process creating the link matches the owner (UID) of the target file (as described in credentials(7), a process's filesystem UID is normally the same as its effective UID).
All of the following conditions are true:
the target is a regular file;
the target file does not have its set-user-ID mode bit enabled;
the target file does not have both its set-group-ID and group-executable mode bits enabled; and
the caller has permission to read and write the target file (either via the file's permissions mask or because it has suitable capabilities).
The default value in this file is 0. Setting the
value to 1 prevents a longstanding class of security
issues caused by hard-link-based time-of-check,
time-of-use races, most commonly seen in
world-writable directories such as /tmp. The common method of
exploiting this flaw is to cross privilege boundaries
when following a given hard link (i.e., a root
process follows a hard link created by another user).
Additionally, on systems without separated
partitions, this stops unauthorized users from
"pinning" vulnerable set-user-ID and set-group-ID
files against being upgraded by the administrator, or
linking to special files.
/proc/sys/fs/protected_symlinks
(since Linux 3.6)When the value in this file is 0, no restrictions are placed on following symbolic links (i.e., this is the historical behavior before Linux 3.6). When the value in this file is 1, symbolic links are followed only in the following circumstances:
the filesystem UID of the process following the link matches the owner (UID) of the symbolic link (as described in credentials(7), a process's filesystem UID is normally the same as its effective UID);
the link is not in a sticky world-writable directory; or
the symbolic link and its parent directory have the same owner (UID)
A system call that fails to follow a symbolic link
because of the above restrictions returns the error
EACCES in errno.
The default value in this file is 0. Setting the value to 1 avoids a longstanding class of security issues based on time-of-check, time-of-use races when accessing symbolic links.
/proc/sys/fs/suid_dumpable (since
Linux 2.6.13)The value in this file is assigned to a process's "dumpable" flag in the circumstances described in prctl(2). In effect, the value in this file determines whether core dump files are produced for set-user-ID or otherwise protected/tainted binaries. Three different integer values can be specified:
- 0 (default)
This provides the traditional (pre-Linux 2.6.13) behavior. A core dump will not be produced for a process which has changed credentials (by calling seteuid(2), setgid(2), or similar, or by executing a set-user-ID or set-group-ID program) or whose binary does not have read permission enabled.
- 1 ("debug")
All processes dump core when possible. The core dump is owned by the filesystem user ID of the dumping process and no security is applied. This is intended for system debugging situations only. Ptrace is unchecked.
- 2 ("suidsafe")
Any binary which normally would not be dumped (see "0" above) is dumped readable by root only. This allows the user to remove the core dump file but not to read it. For security reasons core dumps in this mode will not overwrite one another or other files. This mode is appropriate when administrators are attempting to debug problems in a normal environment.
Additionally, since Linux 3.6,
/proc/sys/kernel/core_patternmust either be an absolute pathname or a pipe command, as detailed in core(5). Warnings will be written to the kernel log ifcore_patterndoes not follow these rules, and no core dump will be produced.
/proc/sys/fs/super-maxThis file controls the maximum number of
superblocks, and thus the maximum number of mounted
filesystems the kernel can have. You need increase
only super-max if you need
to mount more filesystems than the current value in
super-max
allows you to.
/proc/sys/fs/super-nrThis file contains the number of filesystems currently mounted.
/proc/sys/kernelThis directory contains files controlling a range of kernel parameters, as described below.
/proc/sys/kernel/acctThis file contains three numbers: highwater, lowwater, and frequency. If BSD-style process
accounting is enabled, these values control its
behavior. If free space on filesystem where the log
lives goes below lowwater percent, accounting
suspends. If free space gets above highwater percent, accounting
resumes. frequency
determines how often the kernel checks the amount of
free space (value is in seconds). Default values are
4, 2 and 30. That is, suspend accounting if 2% or
less space is free; resume it if 4% or more space is
free; consider information about amount of free space
valid for 30 seconds.
/proc/sys/kernel/auto_msgmni (Linux 2.6.27
to 3.18)From Linux 2.6.27 to 3.18, this file was used to
control recomputing of the value in /proc/sys/kernel/msgmni upon the
addition or removal of memory or upon IPC namespace
creation/removal. Echoing "1" into this file enabled
msgmni automatic
recomputing (and triggered a recomputation of
msgmni based on the
current amount of available memory and number of IPC
namespaces). Echoing "0" disabled automatic
recomputing. (Automatic recomputing was also disabled
if a value was explicitly assigned to /proc/sys/kernel/msgmni.) The
default value in auto_msgmni was 1.
Since Linux 3.19, the content of this file has no
effect (because msgmni
defaults to near the maximum value possible), and
reads from this file always return the value "0".
/proc/sys/kernel/cap_last_cap (since
Linux 3.2)See capabilities(7).
/proc/sys/kernel/cap-bound (from Linux 2.2
to 2.6.24)This file holds the value of the kernel capability bounding set (expressed as a signed decimal number). This set is ANDed against the capabilities permitted to a process during execve(2). Starting with Linux 2.6.25, the system-wide capability bounding set disappeared, and was replaced by a per-thread bounding set; see capabilities(7).
/proc/sys/kernel/core_patternSee core(5).
/proc/sys/kernel/core_pipe_limitSee core(5).
/proc/sys/kernel/core_uses_pidSee core(5).
/proc/sys/kernel/ctrl-alt-delThis file controls the handling of Ctrl-Alt-Del from the keyboard. When the value in this file is 0, Ctrl-Alt-Del is trapped and sent to the init(1) program to handle a graceful restart. When the value is greater than zero, Linux's reaction to a Vulcan Nerve Pinch (tm) will be an immediate reboot, without even syncing its dirty buffers. Note: when a program (like dosemu) has the keyboard in "raw" mode, the ctrl-alt-del is intercepted by the program before it ever reaches the kernel tty layer, and it's up to the program to decide what to do with it.
/proc/sys/kernel/dmesg_restrict
(since Linux 2.6.37)The value in this file determines who can see
kernel syslog contents. A value of 0 in this file
imposes no restrictions. If the value is 1, only
privileged users can read the kernel syslog. (See
syslog(2) for more
details.) Since Linux 3.4, only users with the
CAP_SYS_ADMIN
capability may change the value in this file.
/proc/sys/kernel/domainname and
/proc/sys/kernel/hostnamecan be used to set the NIS/YP domainname and the hostname of your box in exactly the same way as the commands domainname(1) and hostname(1), that is:
# echo 'darkstar' > /proc/sys/kernel/hostname # echo 'mydomain' > /proc/sys/kernel/domainname
has the same effect as
# hostname 'darkstar' # domainname 'mydomain'
Note, however, that the classic darkstar.frop.org has the hostname "darkstar" and DNS (Internet Domain Name Server) domainname "frop.org", not to be confused with the NIS (Network Information Service) or YP (Yellow Pages) domainname. These two domain names are in general different. For a detailed discussion see the hostname(1) man page.
/proc/sys/kernel/hotplugThis file contains the path for the hotplug policy
agent. The default value in this file is /sbin/hotplug.
/proc/sys/kernel/htab-reclaim(PowerPC only) If this file is set to a nonzero
value, the PowerPC htab (see kernel file Documentation/powerpc/ppc_htab.txt)
is pruned each time the system hits the idle
loop.
/proc/sys/kernel/kptr_restrict (since
Linux 2.6.38)The value in this file determines whether kernel
addresses are exposed via /proc files and other interfaces. A
value of 0 in this file imposes no restrictions. If
the value is 1, kernel pointers printed using the
%pK format
specifier will be replaced with zeros unless the user
has the CAP_SYSLOG
capability. If the value is 2, kernel pointers
printed using the %pK format specifier
will be replaced with zeros regardless of the user's
capabilities. The initial default value for this file
was 1, but the default was changed to 0 in Linux
2.6.39. Since Linux 3.4, only users with the
CAP_SYS_ADMIN
capability can change the value in this file.
/proc/sys/kernel/l2cr(PowerPC only) This file contains a flag that controls the L2 cache of G3 processor boards. If 0, the cache is disabled. Enabled if nonzero.
/proc/sys/kernel/modprobeThis file contains the path for the kernel module
loader. The default value is /sbin/modprobe. The file is present
only if the kernel is built with the CONFIG_MODULES (CONFIG_KMOD in Linux 2.6.26 and
earlier) option enabled. It is described by the Linux
kernel source file Documentation/kmod.txt (present
only in kernel 2.4 and earlier).
/proc/sys/kernel/modules_disabled
(since Linux 2.6.31)A toggle value indicating if modules are allowed
to be loaded in an otherwise modular kernel. This
toggle defaults to off (0), but can be set true (1).
Once true, modules can be neither loaded nor
unloaded, and the toggle cannot be set back to false.
The file is present only if the kernel is built with
the CONFIG_MODULES
option enabled.
/proc/sys/kernel/msgmax (since Linux
2.2)This file defines a system-wide limit specifying the maximum number of bytes in a single message written on a System V message queue.
/proc/sys/kernel/msgmni (since Linux
2.4)This file defines the system-wide limit on the
number of message queue identifiers. See also
/proc/sys/kernel/auto_msgmni.
/proc/sys/kernel/msgmnb (since Linux
2.2)This file defines a system-wide parameter used to
initialize the msg_qbytes setting for subsequently
created message queues. The msg_qbytes setting specifies the
maximum number of bytes that may be written to the
message queue.
/proc/sys/kernel/ngroups_max (since
Linux 2.6.4)This is a read-only file that displays the upper limit on the number of a process's group memberships.
/proc/sys/kernel/ostype and
/proc/sys/kernel/osreleaseThese files give substrings of /proc/version.
/proc/sys/kernel/overflowgid and
/proc/sys/kernel/overflowuidThese files duplicate the files /proc/sys/fs/overflowgid and
/proc/sys/fs/overflowuid.
/proc/sys/kernel/panicThis file gives read/write access to the kernel
variable panic_timeout.
If this is zero, the kernel will loop on a panic; if
nonzero, it indicates that the kernel should
autoreboot after this number of seconds. When you use
the software watchdog device driver, the recommended
setting is 60.
/proc/sys/kernel/panic_on_oops (since
Linux 2.5.68)This file controls the kernel's behavior when an
oops or BUG is encountered. If this file contains 0,
then the system tries to continue operation. If it
contains 1, then the system delays a few seconds (to
give klogd time to record the oops output) and then
panics. If the /proc/sys/kernel/panic file is also
nonzero, then the machine will be rebooted.
/proc/sys/kernel/pid_max (since Linux
2.5.34)This file specifies the value at which PIDs wrap
around (i.e., the value in this file is one greater
than the maximum PID). PIDs greater than this value
are not allocated; thus, the value in this file also
acts as a system-wide limit on the total number of
processes and threads. The default value for this
file, 32768, results in the same range of PIDs as on
earlier kernels. On 32-bit platforms, 32768 is the
maximum value for pid_max. On 64-bit systems,
pid_max can be set to
any value up to 2^22 (PID_MAX_LIMIT, approximately 4
million).
/proc/sys/kernel/powersave-nap (PowerPC
only)This file contains a flag. If set, Linux-PPC will use the "nap" mode of powersaving, otherwise the "doze" mode will be used.
/proc/sys/kernel/printkSee syslog(2).
/proc/sys/kernel/pty (since Linux
2.6.4)This directory contains two files relating to the number of UNIX 98 pseudoterminals (see pts(4)) on the system.
/proc/sys/kernel/pty/maxThis file defines the maximum number of pseudoterminals.
/proc/sys/kernel/pty/nrThis read-only file indicates how many pseudoterminals are currently in use.
/proc/sys/kernel/randomThis directory contains various parameters
controlling the operation of the file /dev/random. See random(4) for
further information.
/proc/sys/kernel/random/uuid (since
Linux 2.4)Each read from this read-only file returns a randomly generated 128-bit UUID, as a string in the standard UUID format.
/proc/sys/kernel/randomize_va_space
(since Linux 2.6.12)Select the address space layout randomization (ASLR) policy for the system (on architectures that support ASLR). Three values are supported for this file:
0Turn ASLR off. This is the default for architectures that don't support ASLR, and when the kernel is booted with the
norandmapsparameter.1Make the addresses of mmap(2) allocations, the stack, and the VDSO page randomized. Among other things, this means that shared libraries will be loaded at randomized addresses. The text segment of PIE-linked binaries will also be loaded at a randomized address. This value is the default if the kernel was configured with
CONFIG_COMPAT_BRK.2(Since Linux 2.6.25) Also support heap randomization. This value is the default if the kernel was not configured with
CONFIG_COMPAT_BRK.
/proc/sys/kernel/real-root-devThis file is documented in the Linux kernel source
file Documentation/initrd.txt.
/proc/sys/kernel/reboot-cmd (Sparc
only)This file seems to be a way to give an argument to the SPARC ROM/Flash boot loader. Maybe to tell it what to do after rebooting?
/proc/sys/kernel/rtsig-max(Only in kernels up to and including 2.6.7; see setrlimit(2)) This file can be used to tune the maximum number of POSIX real-time (queued) signals that can be outstanding in the system.
/proc/sys/kernel/rtsig-nr(Only in kernels up to and including 2.6.7.) This file shows the number POSIX real-time signals currently queued.
/proc/sys/kernel/sched_rr_timeslice_ms
(since Linux 3.9)/proc/sys/kernel/sched_rt_period_us
(Since Linux 2.6.25)See sched(7).
/proc/sys/kernel/sched_rt_runtime_us
(Since Linux 2.6.25)See sched(7).
/proc/sys/kernel/sem (since Linux
2.4)This file contains 4 numbers defining limits for System V IPC semaphores. These fields are, in order:
SEMMSLThe maximum semaphores per semaphore set.
SEMMNSA system-wide limit on the number of semaphores in all semaphore sets.
SEMOPMThe maximum number of operations that may be specified in a semop(2) call.
SEMMNIA system-wide limit on the maximum number of semaphore identifiers.
/proc/sys/kernel/sg-big-buffThis file shows the size of the generic SCSI
device (sg) buffer. You can't tune it just yet, but
you could change it at compile time by editing
include/scsi/sg.h and
changing the value of SG_BIG_BUFF. However, there
shouldn't be any reason to change this value.
/proc/sys/kernel/shm_rmid_forced
(since Linux 3.1)If this file is set to 1, all System V shared memory segments will be marked for destruction as soon as the number of attached processes falls to zero; in other words, it is no longer possible to create shared memory segments that exist independently of any attached process.
The effect is as though a shmctl(2)
IPC_RMID is performed
on all existing segments as well as all segments
created in the future (until this file is reset to
0). Note that existing segments that are attached to
no process will be immediately destroyed when this
file is set to 1. Setting this option will also
destroy segments that were created, but never
attached, upon termination of the process that
created the segment with shmget(2).
Setting this file to 1 provides a way of ensuring
that all System V shared memory segments are counted
against the resource usage and resource limits (see
the description of RLIMIT_AS in getrlimit(2)) of at
least one process.
Because setting this file to 1 produces behavior that is nonstandard and could also break existing applications, the default value in this file is 0. Only set this file to 1 if you have a good understanding of the semantics of the applications using System V shared memory on your system.
/proc/sys/kernel/shmall (since Linux
2.2)This file contains the system-wide limit on the total number of pages of System V shared memory.
/proc/sys/kernel/shmmax (since Linux
2.2)This file can be used to query and set the
run-time limit on the maximum (System V IPC) shared
memory segment size that can be created. Shared
memory segments up to 1GB are now supported in the
kernel. This value defaults to SHMMAX.
/proc/sys/kernel/shmmni (since Linux
2.4)This file specifies the system-wide maximum number of System V shared memory segments that can be created.
/proc/sys/kernel/sysctl_writes_strict
(since Linux 3.16)The value in this file determines how the file
offset affects the behavior of updating entries in
files under /proc/sys.
The file has three possible values:
- −1
This provides legacy handling, with no printk warnings. Each write(2) must fully contain the value to be written, and multiple writes on the same file descriptor will overwrite the entire value, regardless of the file position.
0(default) This provides the same behavior as for −1, but printk warnings are written for processes that perform writes when the file offset is not 0.
1Respect the file offset when writing strings into
/proc/sysfiles. Multiple writes willappendto the value buffer. Anything written beyond the maximum length of the value buffer will be ignored. Writes to numeric/proc/sysentries must always be at file offset 0 and the value must be fully contained in the buffer provided to write(2).
/proc/sys/kernel/sysrqThis file controls the functions allowed to be invoked by the SysRq key. By default, the file contains 1 meaning that every possible SysRq request is allowed (in older kernel versions, SysRq was disabled by default, and you were required to specifically enable it at run-time, but this is not the case any more). Possible values in this file are:
0Disable sysrq completely
1Enable all functions of sysrq
- > 1
Bit mask of allowed sysrq functions, as follows:
- 2
Enable control of console logging level
- 4
Enable control of keyboard (SAK, unraw)
- 8
Enable debugging dumps of processes etc.
- 16
Enable sync command
- 32
Enable remount read-only
- 64
Enable signaling of processes (term, kill, oom-kill)
128Allow reboot/poweroff
256Allow nicing of all real-time tasks
This file is present only if the CONFIG_MAGIC_SYSRQ kernel
configuration option is enabled. For further details
see the Linux kernel source file Documentation/sysrq.txt.
/proc/sys/kernel/versionThis file contains a string such as:
#5 Wed Feb 25 21:49:24 MET 1998
The "#5" means that this is the fifth kernel built from this source base and the date following it indicates the time the kernel was built.
/proc/sys/kernel/threads-max (since
Linux 2.3.11)This file specifies the system-wide limit on the number of threads (tasks) that can be created on the system.
Since Linux 4.1, the value that can be written to
threads-max
is bounded. The minimum value that can be written is
20. The maximum value that can be written is given by
the constant FUTEX_TID_MASK (0x3fffffff). If a
value outside of this range is written to threads-max, the
error EINVAL
occurs.
The value written is checked against the available
RAM pages. If the thread structures would occupy too
much (more than 1/8th) of the available RAM pages,
threads-max
is reduced accordingly.
/proc/sys/kernel/yama/ptrace_scope
(since Linux 3.5)See ptrace(2).
/proc/sys/kernel/zero-paged (PowerPC
only)This file contains a flag. When enabled (nonzero), Linux-PPC will pre-zero pages in the idle loop, possibly speeding up get_free_pages.
/proc/sys/netThis directory contains networking stuff. Explanations for some of the files under this directory can be found in tcp(7) and ip(7).
/proc/sys/net/core/bpf_jit_enableSee bpf(2).
/proc/sys/net/core/somaxconnThis file defines a ceiling value for the
backlog argument of
listen(2); see the
listen(2) manual
page for details.
/proc/sys/procThis directory may be empty.
/proc/sys/sunrpcThis directory supports Sun remote procedure call for network filesystem (NFS). On some systems, it is not present.
/proc/sys/vmThis directory contains files for memory management tuning, buffer and cache management.
/proc/sys/vm/compact_memory (since
Linux 2.6.35)When 1 is written to this file, all zones are
compacted such that free memory is available in
contiguous blocks where possible. The effect of this
action can be seen by examining /proc/buddyinfo.
Only present if the kernel was configured with
CONFIG_COMPACTION.
/proc/sys/vm/drop_caches (since Linux
2.6.16)Writing to this file causes the kernel to drop clean caches, dentries, and inodes from memory, causing that memory to become free. This can be useful for memory management testing and performing reproducible filesystem benchmarks. Because writing to this file causes the benefits of caching to be lost, it can degrade overall system performance.
To free pagecache, use:
echo 1 > /proc/sys/vm/drop_caches
To free dentries and inodes, use:
echo 2 > /proc/sys/vm/drop_caches
To free pagecache, dentries and inodes, use:
echo 3 > /proc/sys/vm/drop_caches
Because writing to this file is a nondestructive operation and dirty objects are not freeable, the user should run sync(1) first.
/proc/sys/vm/legacy_va_layout (since
Linux 2.6.9)If nonzero, this disables the new 32-bit memory-mapping layout; the kernel will use the legacy (2.4) layout for all processes.
/proc/sys/vm/memory_failure_early_kill
(since Linux 2.6.32)Control how to kill processes when an uncorrected memory error (typically a 2-bit error in a memory module) that cannot be handled by the kernel is detected in the background by hardware. In some cases (like the page still having a valid copy on disk), the kernel will handle the failure transparently without affecting any applications. But if there is no other up-to-date copy of the data, it will kill processes to prevent any data corruptions from propagating.
The file has one of the following values:
1:Kill all processes that have the corrupted-and-not-reloadable page mapped as soon as the corruption is detected. Note this is not supported for a few types of pages, like kernel internally allocated data or the swap cache, but works for the majority of user pages.
0:Only unmap the corrupted page from all processes and kill only a process that tries to access it.
The kill is performed using a SIGBUS signal with si_code set to BUS_MCEERR_AO. Processes can handle
this if they want to; see sigaction(2) for
more details.
This feature is active only on architectures/platforms with advanced machine check handling and depends on the hardware capabilities.
Applications can override the memory_failure_early_kill setting
individually with the prctl(2)
PR_MCE_KILL
operation.
Only present if the kernel was configured with
CONFIG_MEMORY_FAILURE.
/proc/sys/vm/memory_failure_recovery
(since Linux 2.6.32)Enable memory failure recovery (when supported by the platform)
1:Attempt recovery.
0:Always panic on a memory failure.
Only present if the kernel was configured with
CONFIG_MEMORY_FAILURE.
/proc/sys/vm/oom_dump_tasks (since
Linux 2.6.25)Enables a system-wide task dump (excluding kernel
threads) to be produced when the kernel performs an
OOM-killing. The dump includes the following
information for each task (thread, process): thread
ID, real user ID, thread group ID (process ID),
virtual memory size, resident set size, the CPU that
the task is scheduled on, oom_adj score (see the
description of /proc/[pid]/oom_adj), and command
name. This is helpful to determine why the OOM-killer
was invoked and to identify the rogue task that
caused it.
If this contains the value zero, this information is suppressed. On very large systems with thousands of tasks, it may not be feasible to dump the memory state information for each one. Such systems should not be forced to incur a performance penalty in OOM situations when the information may not be desired.
If this is set to nonzero, this information is shown whenever the OOM-killer actually kills a memory-hogging task.
The default value is 0.
/proc/sys/vm/oom_kill_allocating_task
(since Linux 2.6.24)This enables or disables killing the OOM-triggering task in out-of-memory situations.
If this is set to zero, the OOM-killer will scan through the entire tasklist and select a task based on heuristics to kill. This normally selects a rogue memory-hogging task that frees up a large amount of memory when killed.
If this is set to nonzero, the OOM-killer simply kills the task that triggered the out-of-memory condition. This avoids a possibly expensive tasklist scan.
If /proc/sys/vm/panic_on_oom is
nonzero, it takes precedence over whatever value is
used in /proc/sys/vm/oom_kill_allocating_task.
The default value is 0.
/proc/sys/vm/overcommit_kbytes (since
Linux 3.14)This writable file provides an alternative to
/proc/sys/vm/overcommit_ratio for
controlling the CommitLimit when /proc/sys/vm/overcommit_memory has
the value 2. It allows the amount of memory
overcommitting to be specified as an absolute value
(in kB), rather than as a percentage, as is done with
overcommit_ratio. This
allows for finer-grained control of CommitLimit on systems with
extremely large memory sizes.
Only one of overcommit_kbytes or overcommit_ratio can have an effect:
if overcommit_kbytes has
a nonzero value, then it is used to calculate
CommitLimit, otherwise
overcommit_ratio is
used. Writing a value to either of these files causes
the value in the other file to be set to zero.
/proc/sys/vm/overcommit_memoryThis file contains the kernel virtual memory accounting mode. Values are:
0: heuristic overcommit (this is the default)
1: always overcommit, never check
2: always check, never overcommit
In mode 0, calls of mmap(2) with
MAP_NORESERVE are not
checked, and the default check is very weak, leading
to the risk of getting a process "OOM-killed". Under
Linux 2.4, any nonzero value implies mode 1.
In mode 2 (available since Linux 2.6), the total
virtual address space that can be allocated
(CommitLimit in
/proc/meminfo) is
calculated as
CommitLimit = (total_RAM - total_huge_TLB) * overcommit_ratio / 100 + total_swap
where:
total_RAMis the total amount of RAM on the system;
total_huge_TLBis the amount of memory set aside for huge pages;
overcommit_ratiois the value in/proc/sys/vm/overcommit_ratio; and
total_swapis the amount of swap space.
For example, on a system with 16GB of physical
RAM, 16GB of swap, no space dedicated to huge pages,
and an overcommit_ratio
of 50, this formula yields a CommitLimit of 24GB.
Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes is
nonzero, then CommitLimit is instead calculated
as:
CommitLimit = overcommit_kbytes + total_swap
/proc/sys/vm/overcommit_ratio (since
Linux 2.6.0)This writable file defines a percentage by which
memory can be overcommitted. The default value in the
file is 50. See the description of /proc/sys/vm/overcommit_memory.
/proc/sys/vm/panic_on_oom (since
Linux 2.6.18)This enables or disables a kernel panic in an out-of-memory situation.
If this file is set to the value 0, the kernel's OOM-killer will kill some rogue process. Usually, the OOM-killer is able to kill a rogue process and the system will survive.
If this file is set to the value 1, then the
kernel normally panics when out-of-memory happens.
However, if a process limits allocations to certain
nodes using memory policies (mbind(2)
MPOL_BIND) or cpusets
(cpuset(7)) and
those nodes reach memory exhaustion status, one
process may be killed by the OOM-killer. No panic
occurs in this case: because other nodes' memory may
be free, this means the system as a whole may not
have reached an out-of-memory situation yet.
If this file is set to the value 2, the kernel always panics when an out-of-memory condition occurs.
The default value is 0. 1 and 2 are for failover of clustering. Select either according to your policy of failover.
/proc/sys/vm/swappinessThe value in this file controls how aggressively the kernel will swap memory pages. Higher values increase aggressiveness, lower values decrease aggressiveness. The default value is 60.
/proc/sysrq-trigger (since Linux
2.4.21)Writing a character to this file triggers the same
SysRq function as typing ALT-SysRq-<character>
(see the description of /proc/sys/kernel/sysrq). This file
is normally writable only by root. For further details see the
Linux kernel source file Documentation/sysrq.txt.
/proc/sysvipcSubdirectory containing the pseudo-files
msg, sem and shm. These files list the System V
Interprocess Communication (IPC) objects
(respectively: message queues, semaphores, and shared
memory) that currently exist on the system, providing
similar information to that available via ipcs(1). These
files have headers and are formatted (one IPC object
per line) for easy understanding. svipc(7) provides
further background on the information shown by these
files.
/proc/thread-self (since Linux
3.17)This directory refers to the thread accessing the
/proc filesystem, and
is identical to the /proc/self/task/[tid] directory
named by the process thread ID ([tid]) of the same
thread.
/proc/timer_list (since Linux
2.6.21)This read-only file exposes a list of all currently pending (high-resolution) timers, all clock-event sources, and their parameters in a human-readable form.
/proc/timer_stats (since Linux
2.6.21)This is a debugging facility to make timer (ab)use in a Linux system visible to kernel and user-space developers. It can be used by kernel and user-space developers to verify that their code does not make undue use of timers. The goal is to avoid unnecessary wakeups, thereby optimizing power consumption.
If enabled in the kernel (CONFIG_TIMER_STATS), but not used,
it has almost zero runtime overhead and a relatively
small data-structure overhead. Even if collection is
enabled at runtime, overhead is low: all the locking
is per-CPU and lookup is hashed.
The /proc/timer_stats file is used both
to control sampling facility and to read out the
sampled information.
The timer_stats functionality is inactive on bootup. A sampling period can be started using the following command:
# echo 1 > /proc/timer_stats
The following command stops a sampling period:
# echo 0 > /proc/timer_stats
The statistics can be retrieved by:
$ cat /proc/timer_stats
While sampling is enabled, each readout from
/proc/timer_stats will
see newly updated statistics. Once sampling is
disabled, the sampled information is kept until a new
sample period is started. This allows multiple
readouts.
Sample output from /proc/timer_stats:
$ cat /proc/timer_stats Timer Stats Version: v0.3 Sample period: 1.764 s Collection: active 255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer) 71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer) 58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer) 4, 1694 gnome-shell mod_delayed_work_on (delayed_work_timer_fn) 17, 7 rcu_sched rcu_gp_kthread (process_timeout) ... 1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn) 1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn) 1029 total events, 583.333 events/sec
The output columns are:
a count of the number of events, optionally (since Linux 2.6.23) followed by the letter 'D' if this is a deferrable timer;
the PID of the process that initialized the timer;
the name of the process that initialized the timer;
the function where the timer was initialized; and
(in parentheses) the callback function that is associated with the timer.
/proc/ttySubdirectory containing the pseudo-files and subdirectories for tty drivers and line disciplines.
/proc/uptimeThis file contains two numbers: the uptime of the system (seconds), and the amount of time spent in idle process (seconds).
/proc/versionThis string identifies the kernel version that is
currently running. It includes the contents of
/proc/sys/kernel/ostype,
/proc/sys/kernel/osrelease and
/proc/sys/kernel/version. For
example:
Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994
/proc/vmstat (since Linux
2.6.0)This file displays various virtual memory statistics. Each line of this file contains a single name-value pair, delimited by white space. Some files are present only if the kernel was configured with suitable options. (In some cases, the options required for particular files have changed across kernel versions, so they are not listed here. Details can be found by consulting the kernel source code.) The following fields may be present:
nr_free_pages(since Linux 2.6.31)nr_alloc_batch(since Linux 3.12)nr_inactive_anon(since Linux 2.6.28)nr_active_anon(since Linux 2.6.28)nr_inactive_file(since Linux 2.6.28)nr_active_file(since Linux 2.6.28)nr_unevictable(since Linux 2.6.28)nr_mlock(since Linux 2.6.28)nr_anon_pages(since Linux 2.6.18)nr_mapped(since Linux 2.6.0)nr_file_pages(since Linux 2.6.18)nr_dirty(since Linux 2.6.0)nr_writeback(since Linux 2.6.0)nr_slab_reclaimable(since Linux 2.6.19)nr_slab_unreclaimable(since Linux 2.6.19)nr_page_table_pages(since Linux 2.6.0)nr_kernel_stack(since Linux 2.6.32)Amount of memory allocated to kernel stacks.
nr_unstable(since Linux 2.6.0)nr_bounce(since Linux 2.6.12)nr_vmscan_write(since Linux 2.6.19)nr_vmscan_immediate_reclaim(since Linux 3.2)nr_writeback_temp(since Linux 2.6.26)nr_isolated_anon(since Linux 2.6.32)nr_isolated_file(since Linux 2.6.32)nr_shmem(since Linux 2.6.32)Pages used by shmem and tmpfs.
nr_dirtied(since Linux 2.6.37)nr_written(since Linux 2.6.37)nr_pages_scanned(since Linux 3.17)numa_hit(since Linux 2.6.18)numa_miss(since Linux 2.6.18)numa_foreign(since Linux 2.6.18)numa_interleave(since Linux 2.6.18)numa_local(since Linux 2.6.18)numa_other(since Linux 2.6.18)workingset_refault(since Linux 3.15)workingset_activate(since Linux 3.15)workingset_nodereclaim(since Linux 3.15)nr_anon_transparent_hugepages(since Linux 2.6.38)nr_free_cma(since Linux 3.7)Number of free CMA (Contiguous Memory Allocator) pages.
nr_dirty_threshold(since Linux 2.6.37)nr_dirty_background_threshold(since Linux 2.6.37)pgpgin(since Linux 2.6.0)pgpgout(since Linux 2.6.0)pswpin(since Linux 2.6.0)pswpout(since Linux 2.6.0)pgalloc_dma(since Linux 2.6.5)pgalloc_dma32(since Linux 2.6.16)pgalloc_normal(since Linux 2.6.5)pgalloc_high(since Linux 2.6.5)pgalloc_movable(since Linux 2.6.23)pgfree(since Linux 2.6.0)pgactivate(since Linux 2.6.0)pgdeactivate(since Linux 2.6.0)pgfault(since Linux 2.6.0)pgmajfault(since Linux 2.6.0)pgrefill_dma(since Linux 2.6.5)pgrefill_dma32(since Linux 2.6.16)pgrefill_normal(since Linux 2.6.5)pgrefill_high(since Linux 2.6.5)pgrefill_movable(since Linux 2.6.23)pgsteal_kswapd_dma(since Linux 3.4)pgsteal_kswapd_dma32(since Linux 3.4)pgsteal_kswapd_normal(since Linux 3.4)pgsteal_kswapd_high(since Linux 3.4)pgsteal_kswapd_movable(since Linux 3.4)pgsteal_direct_dmapgsteal_direct_dma32(since Linux 3.4)pgsteal_direct_normal(since Linux 3.4)pgsteal_direct_high(since Linux 3.4)pgsteal_direct_movable(since Linux 2.6.23)pgscan_kswapd_dmapgscan_kswapd_dma32(since Linux 2.6.16)pgscan_kswapd_normal(since Linux 2.6.5)pgscan_kswapd_highpgscan_kswapd_movable(since Linux 2.6.23)pgscan_direct_dmapgscan_direct_dma32(since Linux 2.6.16)pgscan_direct_normalpgscan_direct_highpgscan_direct_movable(since Linux 2.6.23)pgscan_direct_throttle(since Linux 3.6)zone_reclaim_failed(since linux 2.6.31)pginodesteal(since linux 2.6.0)slabs_scanned(since linux 2.6.5)kswapd_inodesteal(since linux 2.6.0)kswapd_low_wmark_hit_quickly(since 2.6.33)kswapd_high_wmark_hit_quickly(since 2.6.33)pageoutrun(since Linux 2.6.0)allocstall(since Linux 2.6.0)pgrotated(since Linux 2.6.0)drop_pagecache(since Linux 3.15)drop_slab(since Linux 3.15)numa_pte_updates(since Linux 3.8)numa_huge_pte_updates(since Linux 3.13)numa_hint_faults(since Linux 3.8)numa_hint_faults_local(since Linux 3.8)numa_pages_migrated(since Linux 3.8)pgmigrate_success(since Linux 3.8)pgmigrate_fail(since Linux 3.8)compact_migrate_scanned(since Linux 3.8)compact_free_scanned(since Linux 3.8)compact_isolated(since Linux 3.8)compact_stall(since Linux 2.6.35)See the kernel source file
Documentation/vm/transhuge.txt.compact_fail(since Linux 2.6.35)See the kernel source file
Documentation/vm/transhuge.txt.compact_success(since Linux 2.6.35)See the kernel source file
Documentation/vm/transhuge.txt.htlb_buddy_alloc_success(since Linux 2.6.26)htlb_buddy_alloc_fail(since Linux 2.6.26)unevictable_pgs_culled(since Linux 2.6.28)unevictable_pgs_scanned(since Linux 2.6.28)unevictable_pgs_rescued(since Linux 2.6.28)unevictable_pgs_mlocked(since Linux 2.6.28)unevictable_pgs_munlocked(since Linux 2.6.28)unevictable_pgs_cleared(since Linux 2.6.28)unevictable_pgs_stranded(since Linux 2.6.28)thp_fault_alloc(since Linux 2.6.39)See the kernel source file
Documentation/vm/transhuge.txt.thp_fault_fallback(since Linux 2.6.39)See the kernel source file
Documentation/vm/transhuge.txt.thp_collapse_alloc(since Linux 2.6.39)See the kernel source file
Documentation/vm/transhuge.txt.thp_collapse_alloc_failed(since Linux 2.6.39)See the kernel source file
Documentation/vm/transhuge.txt.thp_split(since Linux 2.6.39)See the kernel source file
Documentation/vm/transhuge.txt.thp_zero_page_alloc(since Linux 3.8)See the kernel source file
Documentation/vm/transhuge.txt.thp_zero_page_alloc_failed(since Linux 3.8)See the kernel source file
Documentation/vm/transhuge.txt.balloon_inflate(since Linux 3.18)balloon_deflate(since Linux 3.18)balloon_migrate(since Linux 3.18)nr_tlb_remote_flush(since Linux 3.12)nr_tlb_remote_flush_received(since Linux 3.12)nr_tlb_local_flush_all(since Linux 3.12)nr_tlb_local_flush_one(since Linux 3.12)vmacache_find_calls(since Linux 3.16)vmacache_find_hits(since Linux 3.16)vmacache_full_flushes(since Linux 3.19)
/proc/zoneinfo (since Linux
2.6.13)This file display information about memory zones. This is useful for analyzing virtual memory behavior.
Many strings (i.e., the environment and command line) are in the internal format, with subfields terminated by null bytes ('\0'), so you may find that things are more readable if you use od −c or tr"\000" "\n" to read them. Alternatively, echo `cat <file>` works well.
This manual page is incomplete, possibly inaccurate, and is the kind of thing that needs to be updated very often.
cat(1), dmesg(1), find(1), free(1), ps(1), tr(1), uptime(1), chroot(2), mmap(2), readlink(2), syslog(2), slabinfo(5), hier(7), namespaces(7), time(7), arp(8), hdparm(8), ifconfig(8), init(1), lsmod(8), lspci(8), mount(8), netstat(8), procinfo(8), route(8), sysctl(8)
The Linux kernel source files: Documentation/filesystems/proc.txt
Documentation/sysctl/fs.txt,
Documentation/sysctl/kernel.txt,
Documentation/sysctl/net.txt,
and Documentation/sysctl/vm.txt.
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (C) 1994, 1995 by Daniel Quinlan (quinlanyggdrasil.com) and Copyright (C) 2002-2008 Michael Kerrisk <mtk.manpagesgmail.com> with networking additions from Alan Cox (A.Coxswansea.ac.uk) and scsi additions from Michael Neuffer (neuffermail.uni-mainz.de) and sysctl additions from Andries Brouwer (aebcwi.nl) and System V IPC (as well as various other) additions from Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatting or typesetting system, including intermediate and printed output. This manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this manual; if not, see <http://www.gnu.org/licenses/>. %%%LICENSE_END Modified 1995-05-17 by faithcs.unc.edu Minor changes by aeb and Marty Leisner (leisnersdsp.mc.xerox.com). Modified 1996-04-13, 1996-07-22 by aebcwi.nl Modified 2001-12-16 by rwhronearthlink.net Modified 2002-07-13 by jbeltonshaw.ca Modified 2002-07-22, 2003-05-27, 2004-04-06, 2004-05-25 by Michael Kerrisk <mtk.manpagesgmail.com> 2004-11-17, mtk -- updated notes on /proc/loadavg 2004-12-01, mtk, rtsig-max and rtsig-nr went away in 2.6.8 2004-12-14, mtk, updated 'statm', and fixed error in order of list 2005-05-12, mtk, updated 'stat' 2005-07-13, mtk, added /proc/sys/fs/mqueue/* 2005-09-16, mtk, Added /proc/sys/fs/suid_dumpable 2005-09-19, mtk, added /proc/zoneinfo 2005-03-01, mtk, moved /proc/sys/fs/mqueue/* material to mq_overview.7. 2008-06-05, mtk, Added /proc/[pid]/oom_score, /proc/[pid]/oom_adj, /proc/[pid]/limits, /proc/[pid]/mountinfo, /proc/[pid]/mountstats, and /proc/[pid]/fdinfo/*. 2008-06-19, mtk, Documented /proc/[pid]/status. 2008-07-15, mtk, added /proc/config.gz FIXME . cross check against Documentation/filesystems/proc.txt to see what information could be imported from that file into this file. |