.\" 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).
.\"
+.\" SPDX-License-Identifier: GPL-2.0-or-later
+.\"
.\" 2003-08-23 Martin Schulze <joey@infodrom.org> Updated according to glibc 2.3.2
-.TH HOST.CONF 5 2003-08-23 "Linux" "Linux System Administration"
+.TH host.conf 5 (date) "Linux man-pages (unreleased)"
.SH NAME
host.conf \- resolver configuration file
.SH DESCRIPTION
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
-.IR order ", " trim ", " multi ", " nospoof ", " spoof ", and " reorder .
-These keywords are described below.
-.TP
-.I 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
-.IR bind ", " hosts ", and " nis .
+The following keywords are recognized:
.TP
.I trim
This keyword may be listed more than once.
Each time it should be
-followed by a list of domains, separated by colons (\(aq:\(aq), semicolons
-(\(aq;\(aq) or commas (\(aq,\(aq), with the leading dot.
+followed by a list of domains, separated by colons (\[aq]:\[aq]), semicolons
+(\[aq];\[aq]) or commas (\[aq],\[aq]), with the leading dot.
When set, the
-resolv+ library will automatically trim the given domain name from 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.
+(Related note:
+.I trim
+will not affect hostnames gathered via NIS or the
+.BR hosts (5)
+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
.IR on " and " off .
If set to
.IR on ,
-the resolv+ library will return all valid addresses for a host that
+the resolver library will return all valid addresses for a host that
appears in the
.I /etc/hosts
file,
by default, as it may cause a substantial performance loss at sites
with large hosts files.
.TP
-.I nospoof
-Valid values are
-.IR on " and " off .
-If set to
-.IR on ,
-the resolv+ library will attempt to prevent hostname spoofing to
-enhance the security of
-.BR 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
-.IR off .
-.TP
-.I spoofalert
-Valid values are
-.IR on " and " off .
-If this option is set to
-.I on
-and the
-.I nospoof
-option is also set, resolv+ will log a warning of the error via the
-syslog facility.
-The default value is
-.IR off .
-.TP
-.I spoof
-Valid values are
-.IR off ", " nowarn " and " warn .
-If this option is set to
-.IR off ,
-spoofed addresses are permitted and no warnings will be emitted
-via the syslog facility.
-If this option is set to
-.IR 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
-.IR 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
-.IR nowarn .
-.TP
.I reorder
Valid values are
.IR on " and " off .
If set to
.IR on ,
-resolv+ will attempt to reorder host addresses so that local addresses
+the resolver library
+will attempt to reorder host addresses so that local addresses
(i.e., on the same subnet) are listed first when a
.BR gethostbyname (3)
is performed.
The default value is
.IR off .
.SH ENVIRONMENT
-There are six environment variables that can be used to allow users to
+The following environment variables can be used to allow users to
override the behavior which is configured in
-.IR /etc/host.conf .
+.IR /etc/host.conf :
.TP
.B RESOLV_HOST_CONF
-If set this variable points to a file that should be read instead of
+If set, this variable points to a file that should be read instead of
.IR /etc/host.conf .
.TP
-.B RESOLV_SERV_ORDER
-Overrides the
-.I order
-command.
-.TP
-.B RESOLV_SPOOF_CHECK
-Overrides the
-.IR nospoof ", " spoofalert " and " spoof
-commands in the same way as the
-.I spoof
-command is parsed.
-Valid values are
-.IR off ", " nowarn " and " warn .
-.TP
.B RESOLV_MULTI
Overrides the
.I multi
command.
.TP
.B RESOLV_ADD_TRIM_DOMAINS
-A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
-commas (\(aq,\(aq), with the leading dot, which will be added to the list of
-domains that should be trimmed.
+A list of domains,
+separated by
+colons (\[aq]:\[aq]), semicolons (\[aq];\[aq]), or commas (\[aq],\[aq]),
+with the leading dot,
+which will be added to the list of domains that should be trimmed.
.TP
.B RESOLV_OVERRIDE_TRIM_DOMAINS
-A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
-commas (\(aq,\(aq), with the leading dot, which will replace the list of
-domains that should be trimmed.
+A list of domains,
+separated by
+colons (\[aq]:\[aq]), semicolons (\[aq];\[aq]), or commas (\[aq],\[aq]),
+with the leading dot,
+which will replace the list of domains that should be trimmed.
Overrides the
.I trim
command.
and a new environment variable
.B RESOLV_SPOOF_CHECK
can take arguments like
-.IR off ", " nowarn " and " warn .
+.IR off ", " nowarn ", and " warn .
Line comments can appear anywhere and not only at the beginning of a line.
+.SS Historical
+The
+.BR nsswitch.conf (5)
+file is the modern way of controlling the order of host lookups.
+.P
+In glibc 2.4 and earlier, the following keyword is recognized:
+.TP
+.I 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
+.IR bind ", " hosts ", and " nis .
+.TP
+.B RESOLV_SERV_ORDER
+Overrides the
+.I order
+command.
+.P
+.\" commit 7d68cdaa4f748e87ee921f587ee2d483db624b3d
+Since glibc 2.0.7, and up through glibc 2.24,
+the following keywords and environment variable
+have been recognized but never implemented:
+.TP
+.I nospoof
+Valid values are
+.IR on " and " off .
+If set to
+.IR on ,
+the resolver library will attempt to prevent hostname spoofing to
+enhance the security of
+.BR 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 fails.
+The default value is
+.IR off .
+.TP
+.I spoofalert
+Valid values are
+.IR on " and " off .
+If this option is set to
+.I on
+and the
+.I nospoof
+option is also set,
+the resolver library will log a warning of the error via the
+syslog facility.
+The default value is
+.IR off .
+.TP
+.I spoof
+Valid values are
+.IR off ", " nowarn ", and " warn .
+If this option is set to
+.IR off ,
+spoofed addresses are permitted and no warnings will be emitted
+via the syslog facility.
+If this option is set to
+.IR 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
+.IR 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
+.IR nowarn .
+.TP
+.B RESOLV_SPOOF_CHECK
+Overrides the
+.IR nospoof ", " spoofalert ", and " spoof
+commands in the same way as the
+.I spoof
+command is parsed.
+Valid values are
+.IR off ", " nowarn ", and " warn .
.SH SEE ALSO
.BR gethostbyname (3),
+.BR hosts (5),
+.BR nsswitch.conf (5),
+.BR resolv.conf (5),
.BR hostname (7),
-.BR named (8),
-.BR resolv+ (8)
+.BR named (8)
projects / thirdparty / man-pages.git / blobdiff