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diff --git a/man/bootup.xml b/man/bootup.xml deleted file mode 100644 index 986996398c..0000000000 --- a/man/bootup.xml +++ /dev/null @@ -1,305 +0,0 @@ -<?xml version='1.0'?> <!--*-nxml-*--> -<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" - "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> - -<!-- - This file is part of systemd. - - Copyright 2012 Lennart Poettering - - systemd is free software; you can redistribute it and/or modify it - under the terms of the GNU Lesser General Public License as published by - the Free Software Foundation; either version 2.1 of the License, or - (at your option) any later version. - - systemd is distributed in the hope that it will be useful, but - WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public License - along with systemd; If not, see <http://www.gnu.org/licenses/>. ---> - -<refentry id="bootup"> - - <refentryinfo> - <title>bootup</title> - <productname>systemd</productname> - - <authorgroup> - <author> - <contrib>Developer</contrib> - <firstname>Lennart</firstname> - <surname>Poettering</surname> - <email>lennart@poettering.net</email> - </author> - </authorgroup> - </refentryinfo> - - <refmeta> - <refentrytitle>bootup</refentrytitle> - <manvolnum>7</manvolnum> - </refmeta> - - <refnamediv> - <refname>bootup</refname> - <refpurpose>System bootup process</refpurpose> - </refnamediv> - - <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 (optionally) extracts and executes an initial RAM disk - image (initrd), such as generated by - <citerefentry project='die-net'><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 probing all - remaining hardware, mounting all necessary file systems and - spawning all configured services.</para> - - <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 a last step, the system is powered down.</para> - - <para>Additional information about the system boot process may be - found in - <citerefentry project='man-pages'><refentrytitle>boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> - </refsect1> - - <refsect1> - <title>System Manager Bootup</title> - - <para>At boot, the system manager on the OS image is responsible - for initializing the required file 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 steps which - are exposed as target units. (See - <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry> - for detailed information about target units.) The boot-up process - is highly parallelized so that the order in which specific target - units are reached is not deterministic, but still adheres to a - limited amount of ordering structure.</para> - - <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, <filename>default.target</filename> is simply an alias of - <filename>graphical.target</filename> or - <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 target units are available, as listed on - <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> - - <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 near the top are started before units nearer to - the bottom of the chart.</para> - -<programlisting>local-fs-pre.target - | - v -(various mounts and (various swap (various cryptsetup - fsck services...) devices...) devices...) (various low-level (various low-level - | | | services: udevd, API VFS mounts: - v v v tmpfiles, random mqueue, configfs, - local-fs.target swap.target cryptsetup.target seed, sysctl, ...) debugfs, ...) - | | | | | - \__________________|_________________ | ___________________|____________________/ - \|/ - v - sysinit.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 \_________________ | ___________________/ - \|/ - 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> - | | | - \_________________ | _________________/ - \|/ - v - <emphasis>graphical.target</emphasis></programlisting> - - <para>Target units that are commonly used as boot targets are - <emphasis>emphasized</emphasis>. These units are good choices as - goal targets, for example by passing them to the - <varname>systemd.unit=</varname> kernel command line option (see - <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>) - or by symlinking <filename>default.target</filename> to them. - </para> - - <para><filename>timers.target</filename> is pulled-in by - <filename>basic.target</filename> asynchronously. This allows - timers units to depend on services which become only available - later in boot.</para> - </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>. - When the root device becomes available, - <filename>initd-root-device.target</filename> is reached. - 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 - | initrd-root-device.target <emphasis>emergency.target</emphasis> - | | - | v - | sysroot.mount - | | - | 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 with systemd also consists of various target - units with some minimal ordering structure applied:</para> - -<programlisting> (conflicts with (conflicts with - all system all file system - services) mounts, swaps, - | cryptsetup - | devices, ...) - | | - v v - shutdown.target umount.target - | | - \_______ ______/ - \ / - v - (various low-level - services) - | - v - final.target - | - _____________________________________/ \_________________________________ - / | | \ - | | | | - v v v v -systemd-reboot.service systemd-poweroff.service systemd-halt.service systemd-kexec.service - | | | | - v v v v - <emphasis>reboot.target</emphasis> <emphasis>poweroff.target</emphasis> <emphasis>halt.target</emphasis> <emphasis>kexec.target</emphasis></programlisting> - - <para>Commonly used system shutdown targets are - <emphasis>emphasized</emphasis>.</para> - </refsect1> - - <refsect1> - <title>See Also</title> - <para> - <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, - <citerefentry project='man-pages'><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 project='die-net'><refentrytitle>dracut</refentrytitle><manvolnum>8</manvolnum></citerefentry> - </para> - </refsect1> - -</refentry> |