1NSS-MYHOSTNAME(8)               nss-myhostname               NSS-MYHOSTNAME(8)
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NAME

6       nss-myhostname, libnss_myhostname.so.2 - Provide hostname resolution
7       for the locally configured system hostname.
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SYNOPSIS

10       libnss_myhostname.so.2
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DESCRIPTION

13       nss-myhostname is a plug-in module for the GNU Name Service Switch
14       (NSS) functionality of the GNU C Library (glibc), primarily providing
15       hostname resolution for the locally configured system hostname as
16       returned by gethostname(2). The precise hostnames resolved by this
17       module are:
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19       ·   The local, configured hostname is resolved to all locally
20           configured IP addresses ordered by their scope, or — if none are
21           configured — the IPv4 address 127.0.0.2 (which is on the local
22           loopback) and the IPv6 address ::1 (which is the local host).
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24       ·   The hostnames "localhost" and "localhost.localdomain" (as well as
25           any hostname ending in ".localhost" or ".localhost.localdomain")
26           are resolved to the IP addresses 127.0.0.1 and ::1.
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28       ·   The hostname "_gateway" is resolved to all current default routing
29           gateway addresses, ordered by their metric. This assigns a stable
30           hostname to the current gateway, useful for referencing it
31           independently of the current network configuration state.
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33       Various software relies on an always-resolvable local hostname. When
34       using dynamic hostnames, this is traditionally achieved by patching
35       /etc/hosts at the same time as changing the hostname. This is
36       problematic since it requires a writable /etc file system and is
37       fragile because the file might be edited by the administrator at the
38       same time. With nss-myhostname enabled, changing /etc/hosts is
39       unnecessary, and on many systems, the file becomes entirely optional.
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41       To activate the NSS modules, add "myhostname" to the line starting with
42       "hosts:" in /etc/nsswitch.conf.
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44       It is recommended to place "myhostname" last in the nsswitch.conf'
45       "hosts:" line to make sure that this mapping is only used as fallback,
46       and that any DNS or /etc/hosts based mapping takes precedence.
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EXAMPLE

49       Here is an example /etc/nsswitch.conf file that enables nss-myhostname
50       correctly:
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52           passwd:         compat mymachines systemd
53           group:          compat mymachines systemd
54           shadow:         compat
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56           hosts:          files mymachines resolve [!UNAVAIL=return] dns myhostname
57           networks:       files
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59           protocols:      db files
60           services:       db files
61           ethers:         db files
62           rpc:            db files
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64           netgroup:       nis
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66       To test, use glibc's getent tool:
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68           $ getent ahosts `hostname`
69           ::1       STREAM omega
70           ::1       DGRAM
71           ::1       RAW
72           127.0.0.2       STREAM
73           127.0.0.2       DGRAM
74           127.0.0.2       RAW
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76       In this case, the local hostname is omega.
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SEE ALSO

79       systemd(1), nss-systemd(8), nss-resolve(8), nss-mymachines(8),
80       nsswitch.conf(5), getent(1)
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84systemd 239                                                  NSS-MYHOSTNAME(8)
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