💾 Archived View for gmi.noulin.net › man › man5 › host.conf.5.gmi captured on 2024-08-19 at 05:51:45. Gemini links have been rewritten to link to archived content

View Raw

More Information

⬅️ Previous capture (2022-06-12)

-=-=-=-=-=-=-

HOST.CONF(5)                                                           Linux System Administration                                                          HOST.CONF(5)

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 following keywords are recognized:

       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 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(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 installation.)

       multi  Valid  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.

       reorder
              Valid 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.

ENVIRONMENT
       The following environment variables 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_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 argu‐
       ments like off, nowarn, and warn.  Line comments can appear anywhere and not only at the beginning of a line.

   Historical
       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:

       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.

       RESOLV_SERV_ORDER
              Overrides the order command.

       Since glibc 2.0.7, and up through glibc 2.24, the following keywords and environment variable have been recognized but never implemented:

       nospoof
              Valid  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 fails.  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, the resolver library 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  fa‐
              cility.   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_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.

SEE ALSO
       gethostbyname(3), hosts(5), nsswitch.conf(5), resolv.conf(5), hostname(7), named(8)

Linux                                                                          2019-03-06                                                                   HOST.CONF(5)