1 .\" Copyright (c) 1997 Martin Schulze (joey@infodrom.north.de)
2 .\" Much of the text is copied from the manpage of resolv+(8).
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25 .\" 2003-08-23 Martin Schulze <joey@infodrom.org> Updated according to glibc 2.3.2
26 .TH HOST.CONF 5 2003-08-23 "Linux" "Linux System Administration"
28 host.conf \- resolver configuration file
32 contains configuration information specific to the resolver library.
33 It should contain one configuration keyword per line, followed by
34 appropriate configuration information.
35 The keywords recognized are
36 .IR order ", " trim ", " multi ", " nospoof ", " spoof ", and " reorder .
37 These keywords are described below.
40 This keyword specifies how host lookups are to be performed.
41 It should be followed by one or more lookup methods, separated by commas.
43 .IR bind ", " hosts ", and " nis .
46 This keyword may be listed more than once.
47 Each time it should be
48 followed by a list of domains, separated by colons (\(aq:\(aq), semicolons
49 (\(aq;\(aq) or commas (\(aq,\(aq), with the leading dot.
51 resolv+ library will automatically trim the given domain name from the
52 end of any hostname resolved via DNS.
53 This is intended for use with
54 local hosts and domains.
55 (Related note: trim will not affect hostnames
56 gathered via NIS or the hosts file.
57 Care should be taken to
58 ensure that the first hostname for each entry in the hosts file is
59 fully qualified or unqualified, as appropriate for the local
67 the resolv+ library will return all valid addresses for a host that
71 instead of only the first.
74 by default, as it may cause a substantial performance loss at sites
75 with large hosts files.
82 the resolv+ library will attempt to prevent hostname spoofing to
83 enhance the security of
84 .BR rlogin " and " rsh .
85 It works as follows: after performing a host address lookup, resolv+
86 will perform a hostname lookup for that address.
88 do not match, the query will fail.
95 If this option is set to
99 option is also set, resolv+ will log a warning of the error via the
106 .IR off ", " nowarn " and " warn .
107 If this option is set to
109 spoofed addresses are permitted and no warnings will be emitted
110 via the syslog facility.
111 If this option is set to
113 resolv+ will attempt to prevent hostname spoofing to
114 enhance the security and log a warning of the error via the syslog
116 If this option is set to
118 the resolv+ library will attempt to prevent hostname spoofing to
119 enhance the security but not emit warnings via the syslog facility.
120 Setting this option to anything else is equal to setting it to
128 resolv+ will attempt to reorder host addresses so that local addresses
129 (i.e., on the same subnet) are listed first when a
130 .BR gethostbyname (3)
132 Reordering is done for all lookup methods.
136 There are six environment variables that can be used to allow users to
137 override the behavior which is configured in
141 If set, this variable points to a file that should be read instead of
149 .B RESOLV_SPOOF_CHECK
151 .IR nospoof ", " spoofalert " and " spoof
152 commands in the same way as the
156 .IR off ", " nowarn " and " warn .
168 .B RESOLV_ADD_TRIM_DOMAINS
169 A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
170 commas (\(aq,\(aq), with the leading dot, which will be added to the list of
171 domains that should be trimmed.
173 .B RESOLV_OVERRIDE_TRIM_DOMAINS
174 A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
175 commas (\(aq,\(aq), with the leading dot, which will replace the list of
176 domains that should be trimmed.
183 Resolver configuration file
186 Resolver configuration file
191 The following differences exist compared to the original implementation.
194 and a new environment variable
195 .B RESOLV_SPOOF_CHECK
196 can take arguments like
197 .IR off ", " nowarn " and " warn .
198 Line comments can appear anywhere and not only at the beginning of a line.
200 .BR gethostbyname (3),
205 This page is part of release 3.75 of the Linux
208 A description of the project,
209 information about reporting bugs,
210 and the latest version of this page,
212 \%http://www.kernel.org/doc/man\-pages/.