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<?xml version='1.0'?> <!-- * - nxml - * -->
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< !DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX - License - Identifier: LGPL - 2.1 - or - later -->
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<refentry id= "nss-myhostname" conditional= 'ENABLE_NSS_MYHOSTNAME' >
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<refentryinfo >
<title > nss-myhostname</title>
<productname > systemd</productname>
</refentryinfo>
<refmeta >
<refentrytitle > nss-myhostname</refentrytitle>
<manvolnum > 8</manvolnum>
</refmeta>
<refnamediv >
<refname > nss-myhostname</refname>
<refname > libnss_myhostname.so.2</refname>
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<refpurpose > Hostname resolution for the locally configured system hostname</refpurpose>
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</refnamediv>
<refsynopsisdiv >
<para > <filename > libnss_myhostname.so.2</filename> </para>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
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<para > <command > nss-myhostname</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of
the GNU C Library (<command > glibc</command> ), primarily providing hostname resolution for the locally configured
system hostname as returned by
<citerefentry > <refentrytitle > gethostname</refentrytitle> <manvolnum > 2</manvolnum> </citerefentry> . The precise
hostnames resolved by this module are:</para>
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<itemizedlist >
<listitem > <para > The local, configured hostname is resolved to
all locally configured IP addresses ordered by their scope, or
— if none are configured — the IPv4 address 127.0.0.2 (which
is on the local loopback) and the IPv6 address ::1 (which is the
local host).</para> </listitem>
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<listitem > <para > The hostnames <literal > localhost</literal> and
<literal > localhost.localdomain</literal> (as well as any hostname
ending in <literal > .localhost</literal> or <literal > .localhost.localdomain</literal> )
are resolved to the IP addresses 127.0.0.1 and ::1.</para> </listitem>
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<listitem > <para > The hostname <literal > _gateway</literal> is
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resolved to all current default routing gateway addresses,
ordered by their metric. This assigns a stable hostname to the
current gateway, useful for referencing it independently of the
current network configuration state.</para> </listitem>
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<listitem > <para > The hostname <literal > _outbound</literal> is resolved to the local IPv4 and IPv6
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addresses that are most likely used for communication with other hosts. This is the preferred source
addresses of default gateways if specified, or determined by requesting a routing decision to the
configured default gateways from the kernel and then using the local IP addresses selected by this
decision. This hostname is only available if there is at least one local default gateway configured.
This assigns a stable hostname to the local outbound IP addresses, useful for referencing them
independently of the current network configuration state.</para> </listitem>
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</itemizedlist>
<para > Various software relies on an always-resolvable local
hostname. When using dynamic hostnames, this is traditionally
achieved by patching <filename > /etc/hosts</filename> at the same
time as changing the hostname. This is problematic since it
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requires a writable <filename > /etc/</filename> file system and is
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fragile because the file might be edited by the administrator at
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the same time. With <command > nss-myhostname</command> enabled,
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changing <filename > /etc/hosts</filename> is unnecessary, and on
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many systems, the file becomes entirely optional.</para>
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<para > To activate the NSS modules, add <literal > myhostname</literal> to the line starting with
<literal > hosts:</literal> in <filename > /etc/nsswitch.conf</filename> .</para>
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<para > It is recommended to place <literal > myhostname</literal> after <literal > file</literal> and before <literal > dns</literal> .
This resolves well-known hostnames like <literal > localhost</literal>
and the machine hostnames locally. It is consistent with the behaviour
of <command > nss-resolve</command> , and still allows overriding via
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<filename > /etc/hosts</filename> .</para>
<para > Please keep in mind that <command > nss-myhostname</command> (and <command > nss-resolve</command> ) also resolve
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in the other direction — from locally attached IP addresses to
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hostnames. If you rely on that lookup being provided by DNS, you might
want to order things differently.
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</para>
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</refsect1>
<refsect1 >
<title > Example</title>
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<para > Here is an example <filename > /etc/nsswitch.conf</filename> file that enables
<command > nss-myhostname</command> correctly:</para>
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<!-- synchronize with other nss - * man pages and factory/etc/nsswitch.conf -->
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<programlisting > passwd: files systemd
group: files [SUCCESS=merge] systemd
shadow: files systemd
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gshadow: files systemd
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hosts: mymachines resolve [!UNAVAIL=return] files <command > myhostname</command> dns
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networks: files
protocols: db files
services: db files
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ethers: db files
rpc: db files
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netgroup: nis</programlisting>
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man: fix issues reported by the manpage-l10n project
Fixes #25780.
> Man page: crypttab.5
> Issue 1: Missing fullstop
> Issue 2: I<cipher=>, I<hash=>, I<size=> → B<cipher=>, B<hash=>, B<size=>
>
> "Force LUKS mode\\&. When this mode is used, the following options are "
> "ignored since they are provided by the LUKS header on the device: "
> "I<cipher=>, I<hash=>, I<size=>"
Seems OK to me. The full stop is there and has been for at least a few years. And we use <option> for the markup, which is appropriate here.
> Man page: crypttab.5
> Issue 1: Missing fullstop
> Issue 2: I<cipher=>, I<hash=>, I<keyfile-offset=>, I<keyfile-size=>, I<size=> → B<cipher=>, B<hash=>, B<keyfile-offset=>, B<keyfile-size=>, B<size=>
>
> "Use TrueCrypt encryption mode\\&. When this mode is used, the following "
> "options are ignored since they are provided by the TrueCrypt header on the "
> "device or do not apply: I<cipher=>, I<hash=>, I<keyfile-offset=>, I<keyfile-"
> "size=>, I<size=>"
Same.
> Man page: journalctl.1
> Issue 1: make be → may be
Fixed.
> Issue 2: below\\&. → below:
Fixed.
> Man page: journalctl.1
> Issue: Colon at the end?
>
> "The following commands are understood\\&. If none is specified the default "
> "is to display journal records\\&."
> msgstr ""
> "Die folgenden Befehle werden verstanden\\&. Falls keiner festgelegt ist, ist "
> "die Anzeige von Journal-Datensätzen die Vorgabe\\&."
This is a bit awkward, but I'm not sure how to fix it.
> Man page: kernel-install.8
> Issue: methods a fallback → methods fallback
It was correct, but I added a comma to make the sense clearer.
> Man page: loader.conf.5
> Issue 1: secure boot variables → Secure Boot variables
> Issue 2: one → one for (multiple times)
>
> "Supported secure boot variables are one database for authorized images, one "
> "key exchange key (KEK) and one platform key (PK)\\&. For more information, "
> "refer to the \\m[blue]B<UEFI specification>\\m[]\\&\\s-2\\u[2]\\d\\s+2, "
> "under Secure Boot and Driver Signing\\&. Another resource that describe the "
> "interplay of the different variables is the \\m[blue]B<EDK2 "
> "documentation>\\m[]\\&\\s-2\\u[3]\\d\\s+2\\&."
"one of" would sound strange. "One this and one that" is OK.
> Man page: loader.conf.5
> Issue: systemd-boot → B<systemd-boot>(7)
Fixed.
> Man page: logind.conf.5
> Issue: systemd-logind → B<systemd-logind>(8)
We use <filename>systemd-logind</> on subsequent references… I think that's good enough.
> Man page: nss-myhostname.8
> Issue: B<getent> → B<getent>(1)
Fixed.
> Man page: nss-resolve.8
> Issue: B<systemd-resolved> → B<systemd-resolved>(8)
The first reference does this, subsequent are shorter.
> Man page: os-release.5
> Issue: Portable Services → Portable Services Documentation?
Updated.
> Man page: pam_systemd_home.8
> Issue: auth and account use "reason", while session and password do not?
Reworded.
> Man page: portablectl.1
> Issue: In systemd-portabled.service(8): Portable Services Documentation
Updated.
> Man page: repart.d.5
> Issue: The partition → the partition
Fixed.
> Man page: repart.d.5
> Issue: B<systemd-repart> → B<systemd-repart>(8)
The first reference does this. I also change this one, because it's pretty far down in the text.
> Man page: systemd.1
> Issue: kernel command line twice?
>
> "Takes a boolean argument\\&. If false disables importing credentials from "
> "the kernel command line, qemu_fw_cfg subsystem or the kernel command line\\&."
Apparently this was fixed already.
> Man page: systemd-boot.7
> Issue: enrollement → enrollment
Fixed.
> Man page: systemd-cryptenroll.1
> Issue: multiple cases: any specified → the specified
Reworded.
> Man page: systemd-cryptenroll.1
> Issue: If this this → If this
Fixed tree-wide.
> Man page: systemd-cryptsetup-generator.8
> Issue: and the initrd → and in the initrd
"Is honoured by the initrd" is OK, because we often speak about the initrd as a single unit. But in the same paragraph we also used "in the initrd", which makes the other use look sloppy. I changed it to "in the initrd" everywhere in that file.
> Man page: systemd.directives.7
> Issue: Why are these two quoted (but not others)?
>
> "B<\\*(Aqh\\*(Aq>"
>
> B<\\*(Aqs\\*(Aq>"
>
> "B<\\*(Aqy\\*(Aq>"
This is autogenerated from files… We use slightly different markup in different files, and it's just too hard to make it consistent. We gave up on this.
> Man page: systemd.exec.5
> Issue 1: B<at>(1p) → B<at>(1)
> Issue 2: B<crontab>(1p) → B<crontab>(1)
Fixed.
> Man page: systemd.exec.5
> Issue: B<select()> → B<select>(2)
Fixed.
> Man page: systemd.exec.5
> Issue: qemu → B<qemu>(1)
The man page doesn't seem to be in any of the canonical places on the web.
I added a link to online docs.
> Man page: systemd.exec.5
> Issue: variable → variables
Seems to be fixed already.
> Man page: systemd-integritysetup-generator.8
> Issue: systemd-integritysetup-generator → B<systemd-integritysetup-generator>
I changed <filename> to <command>.
> Man page: systemd-integritysetup-generator.8
> Issue: superfluous comma at the end
Already fixed.
> Man page: systemd-measure.1
> Issue: (see B<--pcr-bank=>) below → (see B<--pcr-bank=> below)
Reworded.
> Man page: systemd-measure.1
> Issue: =PATH> → =>I<PATH>
Fixed.
> Man page: systemd-measure.1.po
> Issue: B<--bank=DIGEST> → B<--bank=>I<DIGEST>
Fixed.
> Man page: systemd.netdev.5
> Issue: os the → on the
Appears to have been fixed already.
> Man page: systemd.netdev.5
> Issue: Onboard → On-board (as in previous string)
Updated.
> Man page: systemd.network.5
> Issue: B<systemd-networkd> -> B<systemd-networkd>(8)
First reference does this, subsequent do not.
> Man page: systemd.network.5
> Issue: B<netlabelctl> → B<netlabelctl>(8)
First reference does this, subsequent do not.
> Man page: systemd.network.5
> Issue: Missing verb (aquired? configured?) in the half sentence starting with "or by a "
I dropped the comma.
> Man page: systemd-nspawn.1
> Issue: All host users outside of that range → All other host users
Reworded.
> # FIXME no effect → no effect\\&.
> #. type: Plain text
> #: archlinux debian-unstable fedora-rawhide mageia-cauldron opensuse-tumbleweed
> msgid ""
> "Whichever ID mapping option is used, the same mapping will be used for users "
> "and groups IDs\\&. If B<rootidmap> is used, the group owning the bind "
> "mounted directory will have no effect"
A period is added. Not sure if there's some other issue.
> Man page: systemd-oomd.service.8
> Issue: B<systemd> → B<systemd>(1)
Done.
> Man page: systemd.path.5
> Issue 1: B<systemd.exec>(1) → B<systemd.exec>(5)
> Issue 2: This section does not (yet?) exist
Fixed.
> Man page: systemd-pcrphase.service.8
> Issue 1: indicate phases into TPM2 PCR 11 ??
> Issue 2: Colon at the end of the paragraph?
Fixed.
> Man page: systemd-pcrphase.service.8
> Issue: final boot phase → final shutdown phase?
Updated.
> Man page: systemd-pcrphase.service.8
> Issue: for the the → for the
Fixed tree-wide.
> Man page: systemd-portabled.service.8
> Issue: In systemd-portabled.service(8): Portable Services Documentation
Updated.
> Man page: systemd-pstore.service.8
> Issue: Here and the following paragraphs: . → \\&. // Upstream: What does this comment mean? // You normally write \\&. for a full dot (full stop etc.); here you write only "." (i.e. a plain dot).
>
> "and we look up \"localhost\", nss-dns will send the following queries to "
> "systemd-resolved listening on 127.0.0.53:53: first \"localhost.foobar.com\", "
> "then \"localhost.barbar.com\", and finally \"localhost\". If (hopefully) the "
> "first two queries fail, systemd-resolved will synthesize an answer for the "
> "third query."
Looks all OK to me.
> Man page: systemd.resource-control.5
> Issue: Missing closing bracket after link to Control Groups version 1
Fixed.
> Man page: systemd-sysext.8
> Issue: In systemd-portabled.service(8): Portable Services Documentation
Updated.
> Man page: systemd.timer.5
> Issue 1: B<systemd.exec>(1) → B<systemd.exec>(5)
> Issue 2: This section does not (yet?) exist
Fixed.
> Man page: systemd.unit.5
> Issue: that is → that are
Fixed.
> Man page: systemd-veritysetup-generator.8
> Issue: systemd-veritysetup-generator → B<systemd-veritysetup-generator>
>
> "systemd-veritysetup-generator implements B<systemd.generator>(7)\\&."
>
> "systemd-veritysetup-generator understands the following kernel command line "
> "parameters:"
Updated.
> Man page: systemd-volatile-root.service.8
> Issue: initrdyes → Initrd
Fixed.
> Man page: sysupdate.d.5
> Issue: : → \\&. (As above in TRANSFER)
Updated.
> Man page: sysupdate.d.5
> Issue: some → certain
Updated.
> Man page: sysupdate.d.5
> Issue 1: i\\&.e\\& → I\\&.e\\&
Fixed.
> Issue 2: the image → the system
"image" seems correct.
> Man page: tmpfiles.d.5
> Issue: systemd-tmpfiles → B<systemd-tmpfiles>(8)
Updated.
2023-01-11 18:45:59 +03:00
<para > To test, use <command > glibc</command> 's
<citerefentry project= 'man-pages' > <refentrytitle > getent</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry>
tool:</para>
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<programlisting > $ getent ahosts `hostname`
::1 STREAM omega
::1 DGRAM
::1 RAW
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127.0.0.2 STREAM
127.0.0.2 DGRAM
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127.0.0.2 RAW</programlisting>
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<para > In this case, the local hostname is <varname > omega</varname> .</para>
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</refsect1>
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<refsect1 >
<title > See Also</title>
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<para > <simplelist type= "inline" >
<member > <citerefentry > <refentrytitle > systemd</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> </member>
<member > <citerefentry > <refentrytitle > nss-systemd</refentrytitle> <manvolnum > 8</manvolnum> </citerefentry> </member>
<member > <citerefentry > <refentrytitle > nss-resolve</refentrytitle> <manvolnum > 8</manvolnum> </citerefentry> </member>
<member > <citerefentry > <refentrytitle > nss-mymachines</refentrytitle> <manvolnum > 8</manvolnum> </citerefentry> </member>
<member > <citerefentry project= 'man-pages' > <refentrytitle > nsswitch.conf</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry> </member>
<member > <citerefentry project= 'man-pages' > <refentrytitle > getent</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> </member>
</simplelist> </para>
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</refsect1>
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</refentry>