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Name
host.conf — resolver configuration file
DESCRIPTION
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
keywords recognized are order, trim, multi, nospoof, spoof, and reorder. These keywords are
described below.
order-
This 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.
trim-
This 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 resolv+ 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 non-qualified, as appropriate for the
local installation.)
multi-
Valid values are on and off. If set to
on, the
resolv+ 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.
nospoof-
Valid values are on and off. If set to
on, the
resolv+ 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,
resolv+ will perform a hostname lookup for that
address. If the two hostnames do not match, the query
will fail. The default value is off.
spoofalert-
Valid values are on and off. If this option is
set to on and
the nospoof
option is also set, resolv+ will log a warning of the
error via the syslog facility. The default value is
off.
spoof-
Valid 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, resolv+ 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 resolv+
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.
reorder-
Valid values are on and off. If set to
on, resolv+
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.
ENVIRONMENT
There are six environment variables that can be used to
allow users to override the behavior which is configured in
/etc/host.conf.
RESOLV_HOST_CONF-
If set this variable points to a file that should be
read instead of /etc/host.conf.
RESOLV_SERV_ORDER-
Overrides the order command.
RESOLV_SPOOF_CHECK-
Overrides the nospoof, spoofalert and
spoof
commands in the same way as the spoof command is
parsed. Valid values are off, nowarn and warn.
RESOLV_MULTI-
Overrides the multi command.
RESOLV_REORDER-
Overrides the reorder command.
RESOLV_ADD_TRIM_DOMAINS-
A 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_DOMAINS-
A 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.
FILES
/etc/host.conf-
Resolver configuration file
/etc/resolv.conf-
Resolver configuration file
/etc/hosts-
Local hosts database
NOTES
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.
SEE ALSO
gethostbyname(3),
hostname(7), named(8), resolv+(8)
Copyright (c) 1997 Martin Schulze (joey@infodrom.north.de)
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, write to the Free
Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
USA.
Much of the text is copied from the manpage of resolv+(8).
2003-08-23 Martin Schulze <joey@infodrom.org> Updated according to glibc 2.3.2
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