host.conf — resolver configuration file
The file /etc/host.conf
contains configuration information specific to the resolver
library. It should contain one configuration keyword per
line, followed by appropriate configuration information. The
following keywords are recognized:
trimThis keyword may be listed more than once. Each time it should be followed by a list of domains, separated by colons (':'), semicolons (';') or commas (','), with the leading dot. When set, the resolver library will automatically trim the given domain name from the end of any hostname resolved via DNS. This is intended for use with local hosts and domains. (Related note: trim will not affect hostnames gathered via NIS or the hosts file. Care should be taken to ensure that the first hostname for each entry in the hosts file is fully qualified or unqualified, as appropriate for the local installation.)
multiValid values are on and
off. If set to
on, the resolver library
will return all valid addresses for a host that appears
in the /etc/hosts file,
instead of only the first. This is off by default, as it may cause a
substantial performance loss at sites with large hosts
files.
reorderValid values are on and
off. If set to
on, the resolver library
will attempt to reorder host addresses so that local
addresses (i.e., on the same subnet) are listed first
when a gethostbyname(3) is
performed. Reordering is done for all lookup methods.
The default value is off.
The following environment variables can be used to allow
users to override the behavior which is configured in
/etc/host.conf:
RESOLV_HOST_CONFIf set, this variable points to a file that should
be read instead of /etc/host.conf.
RESOLV_MULTIOverrides the multi
command.
RESOLV_REORDEROverrides the reorder
command.
RESOLV_ADD_TRIM_DOMAINSA list of domains, separated by colons (':'), semicolons (';') or commas (','), with the leading dot, which will be added to the list of domains that should be trimmed.
RESOLV_OVERRIDE_TRIM_DOMAINSA list of domains, separated by colons (':'),
semicolons (';') or commas (','), with the leading dot,
which will replace the list of domains that should be
trimmed. Overrides the trim command.
/etc/host.confResolver configuration file
/etc/resolv.confResolver configuration file
/etc/hostsLocal hosts database
The following differences exist compared to the original
implementation. A new command spoof and a new environment variable
RESOLV_SPOOF_CHECK can take
arguments like off, nowarn and warn. Line comments can appear anywhere and
not only at the beginning of a line.
The nsswitch.conf(5) file is the modern way of controlling the order of host lookups.
In glibc 2.4 and earlier, the following keyword is recognized:
orderThis keyword specifies how host lookups are to be
performed. It should be followed by one or more
lookup methods, separated by commas. Valid methods
are bind, hosts, and nis.
RESOLV_SERV_ORDEROverrides the order command.
Since glibc 2.0.7, the following keywords and environment variable have been recognized but never implemented:
nospoofValid values are on
and off. If set to
on, the resolver library
will attempt to prevent hostname spoofing to enhance
the security of rlogin and
rsh. It
works as follows: after performing a host address
lookup, the resolver library will perform a hostname
lookup for that address. If the two hostnames do not
match, the query will fail. The default value is
off.
spoofalertValid values are on
and off. If this option
is set to on and the
nospoof option is also
set, the resolver library will log a warning of the
error via the syslog facility. The default value is
off.
spoofValid values are off,
nowarn, and warn. If this option is set to
off, spoofed addresses
are permitted and no warnings will be emitted via the
syslog facility. If this option is set to
warn, the resolver
library will attempt to prevent hostname spoofing to
enhance the security and log a warning of the error
via the syslog facility. If this option is set to
nowarn, the resolver
library will attempt to prevent hostname spoofing to
enhance the security but not emit warnings via the
syslog facility. Setting this option to anything else
is equal to setting it to nowarn.
RESOLV_SPOOF_CHECKOverrides the nospoof, spoofalert, and
spoof commands in the
same way as the spoof
command is parsed. Valid values are off, nowarn, and
warn.
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/.
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Copyright (c) 1997 Martin Schulze (joeyinfodrom.north.de) Much of the text is copied from the manpage of resolv+(8). %%%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 2003-08-23 Martin Schulze <joeyinfodrom.org> Updated according to glibc 2.3.2 |