chiark / gitweb /
mount/service: drop FsckPassNo support
[elogind.git] / man / bootup.xml
index 6592352..65c2cee 100644 (file)
         <refsect1>
                 <title>Description</title>
 
-                <para>A number of different components are involved in the
-                system boot. Immediately after power-up, the system
-                BIOS will do minimal hardware initialization, and hand
-                control over to a boot loader stored on a persistent
-                storage device. This boot loader will then invoke an
-                OS kernel from disk (or the network). In the Linux
-                case this kernel now (optionally) extracts and
-                executes an initial RAM disk image (initrd) such as
-                <citerefentry><refentrytitle>dracut</refentrytitle><manvolnum>8</manvolnum></citerefentry>
-                which looks for the root file system. After the root
-                file system is found and mounted the initrd hands over
-                control to the system manager (such as
+                <para>A number of different components are involved in
+                the system boot. Immediately after power-up, the
+                system BIOS will do minimal hardware initialization,
+                and hand control over to a boot loader stored on a
+                persistent storage device. This boot loader will then
+                invoke an OS kernel from disk (or the network). In the
+                Linux case, this kernel (optionally) extracts and
+                executes an initial RAM disk image (initrd), such as
+                generated by
+                <citerefentry><refentrytitle>dracut</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+                which looks for the root file system (possibly using
+                <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                for this). After the root file system is found and
+                mounted, the initrd hands over control to the host's
+                system manager (such as
                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>)
-                stored on the OS image which is then responsible for
+                stored on the OS image, which is then responsible for
                 probing all remaining hardware, mounting all necessary
                 file systems and spawning all configured
                 services.</para>
 
-                <para>On shutdown the system manager stops all
+                <para>On shutdown, the system manager stops all
                 services, unmounts all file systems (detaching the
                 storage technologies backing them), and then
                 (optionally) jumps back into the initrd code which
                 unmounts/detaches the root file system and the storage
-                it resides on. As last step the system is powered down.</para>
+                it resides on. As a last step, the system is powered down.</para>
 
                 <para>Additional information about the system boot
                 process may be found in
@@ -88,7 +91,7 @@
                 systems, services and drivers that are necessary for
                 operation of the system. On
                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
-                systems this process is split up in various discrete
+                systems, this process is split up in various discrete
                 steps which are exposed as target units. (See
                 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                 for detailed information about target units.) The
                 deterministic, but still adheres to a limited amount
                 of ordering structure.</para>
 
-                <para>When systemd starts up the system it will
+                <para>When systemd starts up the system, it will
                 activate all units that are dependencies of
                 <filename>default.target</filename> (as well as
                 recursively all dependencies of these
-                dependencies). Usually
+                dependencies). Usually,
                 <filename>default.target</filename> is simply an alias
                 of <filename>graphical.target</filename> or
-                <filename>multi-user.target</filename> depending on
+                <filename>multi-user.target</filename>, depending on
                 whether the system is configured for a graphical UI or
                 only for a text console. To enforce minimal ordering
-                between the units pulled in a number of well-known
+                between the units pulled in, a number of well-known
                 target units are available, as listed on
                 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 
                                                v
                                         sysinit.target
                                                |
-                             _________________/|\___________________
-                            /                  |                    \
-                            |                  |                    |
-                            v                  |                    v
-                        (various               |              rescue.service
-                       sockets...)             |                    |
-                            |                  |                    v
-                            v                  |              <emphasis>rescue.target</emphasis>
-                     sockets.target            |
-                            |                  |
-                            \_________________ |
-                                              \|
+          ____________________________________/|\________________________________________
+         /                  |                  |                    |                    \
+         |                  |                  |                    |                    |
+         v                  v                  |                    v                    v
+     (various           (various               |                (various          rescue.service
+    timers...)          paths...)              |               sockets...)               |
+         |                  |                  |                    |                    v
+         v                  v                  |                    v              <emphasis>rescue.target</emphasis>
+   timers.target      paths.target             |             sockets.target
+         |                  |                  |                    |
+         \__________________|_________________ | ___________________/
+                                              \|/
                                                v
                                          basic.target
                                                |
-            __________________________________/|                                 emergency.service
-           /                |                  |                                         |
-           |                |                  |                                         v
-           v                v                  v                                 <emphasis>emergency.target</emphasis>
-       display-      (various system    (various system
  manager.service       services           services)
-           |           required for            |
-           |          graphical UIs)           v
-           |                |           <emphasis>multi-user.target</emphasis>
-           |                |                  |
-           \_______________ | _________________/
+          ____________________________________/|                                 emergency.service
+         /                  |                  |                                         |
+         |                  |                  |                                         v
+         v                  v                  v                                 <emphasis>emergency.target</emphasis>
+     display-        (various system    (various system
manager.service         services           services)
+         |             required for            |
+         |            graphical UIs)           v
+         |                  |           <emphasis>multi-user.target</emphasis>
+         |                  |                  |
+         \_________________ | _________________/
                            \|/
                             v
-                    <emphasis>graphical.target</emphasis></programlisting>
+                  <emphasis>graphical.target</emphasis></programlisting>
 
                 <para>Target units that are commonly used as boot
                 targets are <emphasis>emphasized</emphasis>. These
         </refsect1>
 
         <refsect1>
-                <title>Initrd System Manager Bootup</title>
-                <para>The default target in the initrd is the initrd.target. The bootup process is
-                identical to the System Manager Bootup until it reaches basic.target. From there,
-                systemd approaches the special initrd.target. If the root device can be mounted at
-                /sysroot, the sysroot.mount unit becomes active and the initrd-root-fs.target is
-                reached.
-                The initrd-parse-etc.service scans /sysroot/etc/fstab for a possible /usr mountpoint
-                and additional entries marked with the <emphasis>x-initrd.mount</emphasis> option.
-                All entries found are mounted below /sysroot, and the initrd-fs.target is reached.
-                The initrd-cleanup.service isolates to the initrd-switch-root.target, where cleanup
-                services can run. As the very last step, the initrd-switch-root.service is activated,
-                which will cause the system to switch its root to /sysroot.
+                <title>Bootup in the Initial RAM Disk (initrd)</title>
+                <para>The initial RAM disk implementation (initrd) can
+                be set up using systemd as well. In this case, boot up
+                inside the initrd follows the following
+                structure.</para>
+
+                <para>The default target in the initrd is
+                <filename>initrd.target</filename>. The bootup process
+                begins identical to the system manager bootup (see
+                above) until it reaches
+                <filename>basic.target</filename>. From there, systemd
+                approaches the special target
+                <filename>initrd.target</filename>. If the root device
+                can be mounted at <filename>/sysroot</filename>, the
+                <filename>sysroot.mount</filename> unit becomes active
+                and <filename>initrd-root-fs.target</filename> is
+                reached.  The service
+                <filename>initrd-parse-etc.service</filename> scans
+                <filename>/sysroot/etc/fstab</filename> for a possible
+                <filename>/usr</filename> mount point and additional
+                entries marked with the
+                <emphasis>x-initrd.mount</emphasis> option. All
+                entries found are mounted below
+                <filename>/sysroot</filename>, and
+                <filename>initrd-fs.target</filename> is reached. The
+                service <filename>initrd-cleanup.service</filename>
+                isolates to the
+                <filename>initrd-switch-root.target</filename>, where
+                cleanup services can run. As the very last step, the
+                <filename>initrd-switch-root.service</filename> is
+                activated, which will cause the system to switch its
+                root to <filename>/sysroot</filename>.
                 </para>
 
-<programlisting>
-                             (identical to System Manager Bootup)
-                                               :
+<programlisting>                                               : (beginning identical to above)
                                                :
                                                v
                                          basic.target
                        |             initrd-root-fs.target
                        |                       |
                        |                       v
-                       |            initrd-parse-etc.service
-           (custom initrd services)            |
-                       |                       v
+                       v            initrd-parse-etc.service
+                (custom initrd                 |
+                 services...)                  v
                        |            (sysroot-usr.mount and
                        |             various mounts marked
                        |               with fstab option
-                       |                x-initrd.mount)
+                       |              x-initrd.mount...)
                        |                       |
                        |                       v
                        |                initrd-fs.target
                                                |
                                                v
                         ______________________/|
-                       /                       |
+                       /                       v
                        |        initrd-udevadm-cleanup-db.service
-                       |                       |
-           (custom initrd services)            |
-                       |                       |
+                       v                       |
+                (custom initrd                 |
+                 services...)                  |
                        \______________________ |
                                               \|
                                                v
                                    initrd-switch-root.service
                                                |
                                                v
-                                          switch-root
-</programlisting>
+                                     Transition to Host OS</programlisting>
         </refsect1>
 
 
         <refsect1>
                 <title>System Manager Shutdown</title>
 
-                <para>System shutdown also consists of various target
-                units with some minimal ordering structure
-                applied:</para>
+                <para>System shutdown with systemd also consists of
+                various target units with some minimal ordering
+                structure applied:</para>