1HOST.CONF(5) Linux System Administration HOST.CONF(5)
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6 host.conf - resolver configuration file
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9 The file /etc/host.conf contains configuration information specific to
10 the resolver library. It should contain one configuration keyword per
11 line, followed by appropriate configuration information. The keywords
12 recognized are order, trim, multi, nospoof, spoof, and reorder. These
13 keywords are described below.
14 order This keyword specifies how host lookups are to be performed. It
17 should be followed by one or more lookup methods, separated by
18 commas. Valid methods are bind, hosts, and nis.
19 trim This keyword may be listed more than once. Each time it should
21 be followed by a list of domains, separated by colons (`:'),
22 semicolons (`;') or commas (`,'), with the leading dot. When
23 set, the resolv+ library will automatically trim the given
24 domain name from the end of any hostname resolved via DNS. This
25 is intended for use with local hosts and domains. (Related
26 note: trim will not affect hostnames gathered via NIS or the
27 hosts file. Care should be taken to ensure that the first host‐
28 name for each entry in the hosts file is fully qualified or non-
29 qualified, as appropriate for the local installation.)
30 multi Valid values are on and off. If set to on, the resolv+ library
32 will return all valid addresses for a host that appears in the
33 /etc/hosts file, instead of only the first. This is off by
34 default, as it may cause a substantial performance loss at sites
35 with large hosts files.
36 nospoof
38 Valid values are on and off. If set to on, the resolv+ library
39 will attempt to prevent hostname spoofing to enhance the secu‐
40 rity of rlogin and rsh. It works as follows: after performing a
41 host address lookup, resolv+ will perform a hostname lookup for
42 that address. If the two hostnames do not match, the query will
43 fail. The default value is off.
44 spoofalert
46 Valid values are on and off. If this option is set to on and
47 the nospoof option is also set, resolv+ will log a warning of
48 the error via the syslog facility. The default value is off.
49 spoof Valid values are off, nowarn and warn. If this option is set to
51 off, spoofed addresses are permitted and no warnings will be
52 emitted via the syslog facility. If this option is set to warn,
53 resolv+ will attempt to prevent hostname spoofing to enhance the
54 security and log a warning of the error via the syslog facility.
55 If this option is set to nowarn, the resolv+ library will
56 attempt to prevent hostname spoofing to enhance the security but
57 not emit warnings via the syslog facility. Setting this option
58 to anything else is equal to setting it to nowarn.
59 reorder
61 Valid values are on and off. If set to on, resolv+ will attempt
62 to reorder host addresses so that local addresses (i.e., on the
63 same subnet) are listed first when a gethostbyname(3) is per‐
64 formed. Reordering is done for all lookup methods. The default
65 value is off.
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68 There are six environment variables that can be used to allow users to
69 override the behavior which is configured in /etc/host.conf.
70 RESOLV_HOST_CONF
72 If set this variable points to a file that should be read
73 instead of /etc/host.conf.
74 RESOLV_SERV_ORDER
76 Overrides the order command.
77 RESOLV_SPOOF_CHECK
79 Overrides the nospoof, spoofalert and spoof commands in the same
80 way as the spoof command is parsed. Valid values are off,
81 nowarn and warn.
82 RESOLV_MULTI
84 Overrides the multi command.
85 RESOLV_REORDER
87 Overrides the reorder command.
88 RESOLV_ADD_TRIM_DOMAINS
90 A list of domains, separated by colons (`:'), semicolons (`;')
91 or commas (`,'), with the leading dot, which will be added to
92 the list of domains that should be trimmed.
93 RESOLV_OVERRIDE_TRIM_DOMAINS
95 A list of domains, separated by colons (`:'), semicolons (`;')
96 or commas (`,'), with the leading dot, which will replace the
97 list of domains that should be trimmed. Overrides the trim com‐
98 mand.
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101 /etc/host.conf
102 Resolver configuration file
103 /etc/resolv.conf
105 Resolver configuration file
106 /etc/hosts
108 Local hosts database
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111 The following differences exist compared to the original implementa‐
112 tion. A new command spoof and a new environment variable
113 RESOLV_SPOOF_CHECK can take arguments like off, nowarn and warn. Line
114 comments can appear anywhere and not only at the beginning of a line.
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117 gethostbyname(3), hostname(7), named(8), resolv+[22m(8)
118Debian GNU/Linux 2003-08-23 HOST.CONF(5)