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<refentry id="systemd-machine-id-commit.service">
- <refentryinfo>
- <title>systemd-machine-id-commit.service</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Didier</firstname>
- <surname>Roche</surname>
- <email>didrocks@ubuntu.com</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>systemd-machine-id-commit.service</refentrytitle>
- <manvolnum>8</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>systemd-machine-id-commit.service</refname>
- <refpurpose>Commit transient machine-id to disk</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <para><filename>systemd-machine-id-commit.service</filename></para>
- <para><filename>/usr/lib/systemd/systemd-machine-id-commit</filename></para>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><filename>systemd-machine-id-commit.service</filename> is
- a service responsible for commiting any transient
- <filename>/etc/machine-id</filename> file to a writable file
- system. See
- <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for more information about this file.</para>
-
- <para>This service is started shortly after
- <filename>local-fs.target</filename> if
- <filename>/etc/machine-id</filename> is an independent mount
- point (probably a tmpfs one) and /etc is writable.
- <command>systemd-machine-id-commit</command> will then
- write current machine ID to disk and unmount the transient
- <filename>/etc/machine-id</filename> file in a race-free
- manner to ensure that file is always valid for other
- processes.</para>
-
- <para>Note that the traditional way to initialize the machine
- ID in <filename>/etc/machine-id</filename> is to use
- <command>systemd-machine-id-setup</command> by system
- installer tools. You can also use
- <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- to initialize the machine ID on mounted (but not
- booted) system images. The main use case for that service is
- <filename>/etc/machine-id</filename> being an empty file at
- boot and initrd chaining to systemd giving it a read only file
- system that will be turned read-write later during the boot
- process.</para>
-
- <para>There is no consequence if that service fails other than
- a newer machine-id will be generated during next system boot.
- </para>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd-machine-id-commit</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- </para>
- </refsect1>
+ <refentryinfo>
+ <title>systemd-machine-id-commit.service</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Didier</firstname>
+ <surname>Roche</surname>
+ <email>didrocks@ubuntu.com</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>systemd-machine-id-commit.service</refentrytitle>
+ <manvolnum>8</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd-machine-id-commit.service</refname>
+ <refpurpose>Commit a transient machine ID to disk</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename>systemd-machine-id-commit.service</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><filename>systemd-machine-id-commit.service</filename> is an
+ early boot service responsible for committing transient
+ <filename>/etc/machine-id</filename> files to a writable disk file
+ system. See
+ <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for more information about machine IDs.</para>
+
+ <para>This service is started after
+ <filename>local-fs.target</filename> in case
+ <filename>/etc/machine-id</filename> is a mount point of its own
+ (usually from a memory file system such as
+ <literal>tmpfs</literal>) and /etc is writable. The service will
+ invoke <command>systemd-machine-id-setup --commit</command>, which
+ writes the current transient machine ID to disk and unmount the
+ <filename>/etc/machine-id</filename> file in a race-free manner to
+ ensure that file is always valid and accessible for other
+ processes. See
+ <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ for details.</para>
+
+ <para>The main use case of this service are systems where
+ <filename>/etc/machine-id</filename> is read-only and initially
+ not initialized. In this case, the system manager will generate a
+ transient machine ID file on a memory file system, and mount it
+ over <filename>/etc/machine-id</filename>, during the early boot
+ phase. This service is then invoked in a later boot phase, as soon
+ as <filename>/etc</filename> has been remounted writable and the
+ ID may thus be committed to disk to make it permanent.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
projects / thirdparty / systemd.git / blobdiff