Originální popis anglicky:
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 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.
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.
- /etc/host.conf
- Resolver configuration file
- /etc/resolv.conf
- Resolver configuration file
- /etc/hosts
- Local 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.
gethostbyname(3),
hostname(7),
named(8),
resolv+(8)
