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Systemd/man/kernel-command-line.xml
Franck Bui c6885f5f36 core: introduce systemd.early_core_pattern= kernel cmdline option 
Until a core dump handler is installed by systemd-sysctl, the generation of
core dump for services is turned OFF which can make the debugging of the early
boot process harder especially since there's no easy way to restore the core
dump generation.

This patch introduces a new kernel command line option which specifies an
absolute path where the kernel should write the core dump file when an early
process crashes.

This will take effect until systemd-coredump (or any other handlers) takes
over.
2018-10-09 10:26:23 +02:00

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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">
<!--
SPDX-License-Identifier: LGPL-2.1+
-->
<refentry id="kernel-command-line">
<refentryinfo>
<title>kernel-command-line</title>
<productname>systemd</productname>
</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/html/latest/admin-guide/kernel-parameters.html"><filename>kernel-parameters.html</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.early_core_pattern=</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.service_watchdogs</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_location=</varname></term>
<term><varname>systemd.log_color</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>
<term><varname>systemd.unified_cgroup_hierarchy</varname></term>
<term><varname>systemd.legacy_systemd_cgroup_controller</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.early_core_pattern=</varname></term>
<listitem>
<para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
takes over. This parameter allows to specifies an absolute path where core dump files should be stored until
a handler is installed. The path should be absolute and may contain specifiers, see
<citerefentry><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</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>mount.usr=</varname></term>
<term><varname>mount.usrfstype=</varname></term>
<term><varname>mount.usrflags=</varname></term>
<listitem>
<para>Configures the /usr file system (if required) and
its file system type and mount options. For details, see
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>roothash=</varname></term>
<term><varname>systemd.verity=</varname></term>
<term><varname>rd.systemd.verity=</varname></term>
<term><varname>systemd.verity_root_data=</varname></term>
<term><varname>systemd.verity_root_hash=</varname></term>
<listitem>
<para>Configures the integrity protection root hash for the root file system, and other related
parameters. For details, see
<citerefentry><refentrytitle>systemd-veritysetup-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>systemd.watchdog_device=</varname></term>
<listitem>
<para>Overwrites the watchdog device path <varname>WatchdogDevice=</varname>. 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-veritysetup-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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