target units are available, as listed on
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
- <para>The follow chart is a structural overview of
+ <para>The following chart is a structural overview of
these well-known units and their position in the
boot-up logic. The arrows describe which units are
pulled in and ordered before which other units. Units
to them.</para>
</refsect1>
+ <refsect1>
+ <title>Systemd in the Initrd</title>
+ <para>If the initrd creation tool used the services provided
+ by systemd, the default target in the initrd is the
+ initrd-fs.target. The process is the same as above until the basic.target is reached.
+ Systemd now continues to the initrd.target. If the root device could be mounted
+ on /sysroot, the sysroot.mount unit is active and the initrd-root-fs.target is reached.
+ initrd-parse-etc.service scans /sysroot/etc/fstab for the /usr mountpoint and for entries
+ marked with the <emphasis>x-initrd.mount</emphasis> option set. If these mountpoint are
+ mounted in /sysroot, the initrd-fs.target is reached.
+ The initrd-cleanup.service isolates to the initrd-switch-root.target,
+ where cleanup services can run. At the very last end
+ initrd-switch-root.service is activated, which will cause
+ the system to switch root to /sysroot.
+ </para>
+
+<programlisting>
+ (same as above)
+ :
+ :
+ v
+ basic.target
+ | emergency.service
+ ______________________/| |
+ / | v
+ | sysroot.mount <emphasis>emergency.target</emphasis>
+ | |
+ | v
+ | initrd-root-fs.target
+ | |
+ | v
+ | initrd-parse-etc.service
+ (custom initrd services) |
+ | v
+ | (sysroot-usr.mount and
+ | various mounts marked
+ | with fstab option
+ | x-initrd.mount)
+ | |
+ | v
+ | initrd-fs.target
+ | |
+ \______________________ |
+ \|
+ v
+ initrd.target
+ |
+ v
+ initrd-cleanup.service
+ isolates to
+ initrd-switch-root.target
+ |
+ v
+ ______________________/|
+ / |
+ | initrd-udevadm-cleanup-db.service
+ | |
+ (custom initrd services) |
+ | |
+ \______________________ |
+ \|
+ v
+ initrd-switch-root.target
+ |
+ v
+ initrd-switch-root.service
+ |
+ v
+ switch-root
+</programlisting>
+ </refsect1>
+
+
<refsect1>
<title>System Manager Shutdown</title>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>dracut</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>