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Systemd/man/kernel-command-line.xml
Lennart Poettering 91214a37ef fstab-generator: add support for volatile boots 
This adds support for a new kernel command line option "systemd.volatile=" that
provides the same functionality that systemd-nspawn's --volatile= switch
provides, but for host systems (i.e. systems booting with a kernel).

It takes the same parameter and has the same effect.

In order to implement systemd.volatile=yes a new service
systemd-volatile-root.service is introduced that only runs in the initrd and
rearranges the root directory as needed to become a tmpfs instance. Note that
systemd.volatile=state is implemented different: it simply generates a
var.mount unit file that is part of the normal boot and has no effect on the
initrd execution.

The way this is implemented ensures that other explicit configuration for /var
can always override the effect of these options.  Specifically, the var.mount
unit is generated in the "late" generator directory, so that it only is in
effect if nothing else overrides it.
2016-12-21 19:09:29 +01:00

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<?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
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(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
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You should have received a copy of the GNU Lesser General Public License
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<refentry id="kernel-command-line">
<refentryinfo>
<title>kernel-command-line</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>kernel-command-line</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>kernel-command-line</refname>
<refpurpose>Kernel command line parameters</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>/proc/cmdline</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>The kernel, the initial RAM disk (initrd) and
basic userspace functionality may be configured at boot via
kernel command line arguments.</para>
<para>For command line parameters understood by the kernel, please
see <ulink
url="https://www.kernel.org/doc/Documentation/kernel-parameters.txt"><filename>kernel-parameters.txt</filename></ulink>
and
<citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
<para>For command line parameters understood by the initial RAM
disk, please see
<citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
or the documentation of the specific initrd implementation of your
installation.</para>
</refsect1>
<refsect1>
<title>Core OS Command Line Arguments</title>
<variablelist class='kernel-commandline-options'>
<varlistentry>
<term><varname>systemd.unit=</varname></term>
<term><varname>rd.systemd.unit=</varname></term>
<term><varname>systemd.dump_core=</varname></term>
<term><varname>systemd.crash_chvt=</varname></term>
<term><varname>systemd.crash_shell=</varname></term>
<term><varname>systemd.crash_reboot=</varname></term>
<term><varname>systemd.confirm_spawn=</varname></term>
<term><varname>systemd.show_status=</varname></term>
<term><varname>systemd.log_target=</varname></term>
<term><varname>systemd.log_level=</varname></term>
<term><varname>systemd.log_color=</varname></term>
<term><varname>systemd.log_location=</varname></term>
<term><varname>systemd.default_standard_output=</varname></term>
<term><varname>systemd.default_standard_error=</varname></term>
<term><varname>systemd.setenv=</varname></term>
<term><varname>systemd.machine_id=</varname></term>
<listitem>
<para>Parameters understood by the system and service
manager to control system behavior. For details, see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.mask=</varname></term>
<term><varname>systemd.wants=</varname></term>
<term><varname>systemd.debug_shell</varname></term>
<listitem>
<para>Additional parameters understood by
<citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
to mask or start specific units at boot, or invoke a debug
shell on tty9.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.restore_state=</varname></term>
<listitem>
<para>This parameter is understood by several system tools
to control whether or not they should restore system state
from the previous boot. For details, see
<citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.volatile=</varname></term>
<listitem>
<para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
directory and <filename>/var</filename> are mounted as specified on the kernel command line or
<filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
<filename>/usr</filename> is mounted from the file system configured as root device, in read-only mode. This
enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
configuration and no stored state in effect, as <filename>/etc</filename> and <filename>/var</filename> (as
well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
setting is set to <literal>state</literal> the root file system is mounted as usual, however
<filename>/var</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. For details,
see
<citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>quiet</varname></term>
<listitem>
<para>Parameter understood by both the kernel and the system
and service manager to control console log verbosity. For
details, see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>debug</varname></term>
<listitem>
<para>Parameter understood by both the kernel and the system
and service manager to control console log verbosity. For
details, see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>-b</varname></term>
<term><varname>rd.emergency</varname></term>
<term><varname>emergency</varname></term>
<term><varname>rd.rescue</varname></term>
<term><varname>rescue</varname></term>
<term><varname>single</varname></term>
<term><varname>s</varname></term>
<term><varname>S</varname></term>
<term><varname>1</varname></term>
<term><varname>2</varname></term>
<term><varname>3</varname></term>
<term><varname>4</varname></term>
<term><varname>5</varname></term>
<listitem>
<para>Parameters understood by the system and service
manager, as compatibility and convenience options. For details, see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>locale.LANG=</varname></term>
<term><varname>locale.LANGUAGE=</varname></term>
<term><varname>locale.LC_CTYPE=</varname></term>
<term><varname>locale.LC_NUMERIC=</varname></term>
<term><varname>locale.LC_TIME=</varname></term>
<term><varname>locale.LC_COLLATE=</varname></term>
<term><varname>locale.LC_MONETARY=</varname></term>
<term><varname>locale.LC_MESSAGES=</varname></term>
<term><varname>locale.LC_PAPER=</varname></term>
<term><varname>locale.LC_NAME=</varname></term>
<term><varname>locale.LC_ADDRESS=</varname></term>
<term><varname>locale.LC_TELEPHONE=</varname></term>
<term><varname>locale.LC_MEASUREMENT=</varname></term>
<term><varname>locale.LC_IDENTIFICATION=</varname></term>
<listitem>
<para>Parameters understood by the system and service
manager to control locale and language settings. For
details, see
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>fsck.mode=</varname></term>
<term><varname>fsck.repair=</varname></term>
<listitem>
<para>Parameters understood by the file system checker
services. For details, see
<citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>quotacheck.mode=</varname></term>
<listitem>
<para>Parameter understood by the file quota checker
service. For details, see
<citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.journald.forward_to_syslog=</varname></term>
<term><varname>systemd.journald.forward_to_kmsg=</varname></term>
<term><varname>systemd.journald.forward_to_console=</varname></term>
<term><varname>systemd.journald.forward_to_wall=</varname></term>
<listitem>
<para>Parameters understood by the journal service. For
details, see
<citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>vconsole.keymap=</varname></term>
<term><varname>vconsole.keymap_toggle=</varname></term>
<term><varname>vconsole.font=</varname></term>
<term><varname>vconsole.font_map=</varname></term>
<term><varname>vconsole.font_unimap=</varname></term>
<listitem>
<para>Parameters understood by the virtual console setup logic. For details, see
<citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>udev.log_priority=</varname></term>
<term><varname>rd.udev.log_priority=</varname></term>
<term><varname>udev.children_max=</varname></term>
<term><varname>rd.udev.children_max=</varname></term>
<term><varname>udev.exec_delay=</varname></term>
<term><varname>rd.udev.exec_delay=</varname></term>
<term><varname>udev.event_timeout=</varname></term>
<term><varname>rd.udev.event_timeout=</varname></term>
<term><varname>net.ifnames=</varname></term>
<listitem>
<para>Parameters understood by the device event managing
daemon. For details, see
<citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>plymouth.enable=</varname></term>
<listitem>
<para>May be used to disable the Plymouth boot splash. For
details, see
<citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>luks=</varname></term>
<term><varname>rd.luks=</varname></term>
<term><varname>luks.crypttab=</varname></term>
<term><varname>rd.luks.crypttab=</varname></term>
<term><varname>luks.name=</varname></term>
<term><varname>rd.luks.name=</varname></term>
<term><varname>luks.uuid=</varname></term>
<term><varname>rd.luks.uuid=</varname></term>
<term><varname>luks.options=</varname></term>
<term><varname>rd.luks.options=</varname></term>
<term><varname>luks.key=</varname></term>
<term><varname>rd.luks.key=</varname></term>
<listitem>
<para>Configures the LUKS full-disk encryption logic at
boot. For details, see
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>fstab=</varname></term>
<term><varname>rd.fstab=</varname></term>
<listitem>
<para>Configures the <filename>/etc/fstab</filename> logic
at boot. For details, see
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>root=</varname></term>
<term><varname>rootfstype=</varname></term>
<term><varname>rootflags=</varname></term>
<term><varname>ro</varname></term>
<term><varname>rw</varname></term>
<listitem>
<para>Configures the root file system and its file system
type and mount options, as well as whether it shall be
mounted read-only or read-writable initially. For details,
see
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.gpt_auto=</varname></term>
<term><varname>rd.systemd.gpt_auto=</varname></term>
<listitem>
<para>Configures whether GPT based partition auto-discovery
shall be attempted. For details, see
<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.default_timeout_start_sec=</varname></term>
<listitem>
<para>Overwrites the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at boot. For details,
see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>modules_load=</varname></term>
<term><varname>rd.modules_load=</varname></term>
<listitem>
<para>Load a specific kernel module early at boot. For
details, see
<citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>resume=</varname></term>
<listitem>
<para>Enables resume from hibernation using the specified
device. All
<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
paths are supported. For details, see
<citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.firstboot=</varname></term>
<listitem><para>Takes a boolean argument, defaults to on. If off,
<citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
will not query the user for basic system settings, even if the system boots up for the first time and the
relevant settings are not initialized yet.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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