diff options
Diffstat (limited to 'man/bootup.xml')
| -rw-r--r-- | man/bootup.xml | 167 |
1 files changed, 129 insertions, 38 deletions
diff --git a/man/bootup.xml b/man/bootup.xml index 4cc4bafab7..a596e85b70 100644 --- a/man/bootup.xml +++ b/man/bootup.xml @@ -50,18 +50,20 @@ <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 + <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 <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 + 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 probing all remaining hardware, mounting all necessary @@ -132,35 +134,35 @@ 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 @@ -174,11 +176,99 @@ </refsect1> <refsect1> + <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> : (beginning identical to above) + : + v + basic.target + | emergency.service + ______________________/| | + / | v + | sysroot.mount <emphasis>emergency.target</emphasis> + | | + | v + | initrd-root-fs.target + | | + | v + 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 + ______________________/| + / v + | initrd-udevadm-cleanup-db.service + v | + (custom initrd | + services...) | + \______________________ | + \| + v + initrd-switch-root.target + | + v + initrd-switch-root.service + | + v + 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> @@ -219,7 +309,8 @@ systemd-reboot.service systemd-poweroff.service systemd-halt.service syste <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> |