Difference between revisions of "Systemd"

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(→‎Using display manager: this is a *partial* workaround for a bug in some DMs (unrelated to systemd), if your display manager does not source /etc/profile it is a bug you should report)
(Added a summarizing sentence in the beginning of the Target section. Lesser experienced user may have problems with the current approach of comparing it to runlevels which seems to be an rather outdated concept.)
 
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[[Category:Daemons and system services]]
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[[Category:Daemons]]
[[Category:Boot process]]
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[[Category:Init]]
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[[ar:Systemd]]
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[[de:Systemd]]
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[[el:Systemd]]
 
[[es:Systemd]]
 
[[es:Systemd]]
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[[fr:Systemd]]
 
[[fr:Systemd]]
 
[[it:Systemd]]
 
[[it:Systemd]]
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[[ja:Systemd]]
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[[pt:Systemd]]
 
[[ru:Systemd]]
 
[[ru:Systemd]]
[[zh-CN:Systemd]]
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[[zh-hans:Systemd]]
{{Article summary start}}
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[[zh-hant:Systemd]]
{{Article summary text|Covers how to install and configure systemd.}}
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{{Related articles start}}
{{Article summary heading|Related}}
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{{Related|systemd/User}}
{{Article summary wiki|Systemd/Services}}
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{{Related|systemd/Timers}}
{{Article summary wiki|Init to systemd cheatsheet}}
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{{Related|systemd/Journal}}
{{Article summary end}}
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{{Related|systemd FAQ}}
From the [http://freedesktop.org/wiki/Software/systemd project web page]:
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{{Related|init}}
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{{Related|Daemons}}
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{{Related|udev}}
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{{Related|Improving performance/Boot process}}
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{{Related|Allow users to shutdown}}
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{{Related articles end}}
  
''"'''systemd''' is a system and service manager for Linux, compatible with SysV and LSB init scripts. systemd provides aggressive parallelization capabilities, uses socket and [[D-Bus]] activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux [[cgroups]], supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic. It can work as a drop-in replacement for sysvinit."''
+
From the [https://freedesktop.org/wiki/Software/systemd/ project web page]:
  
{{Note|For a detailed explanation as to why Arch is switching to systemd, see: [https://bbs.archlinux.org/viewtopic.php?pid=1149530#p1149530 this forum post].}}
+
:''systemd'' is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system. systemd provides aggressive parallelization capabilities, uses socket and [[D-Bus]] activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux [[control groups]], maintains mount and automount points, and implements an elaborate transactional dependency-based service control logic. ''systemd'' supports SysV and LSB init scripts and works as a replacement for sysvinit. Other parts include a logging daemon, utilities to control basic system configuration like the hostname, date, locale, maintain a list of logged-in users and running containers and virtual machines, system accounts, runtime directories and settings, and daemons to manage simple network configuration, network time synchronization, log forwarding, and name resolution.
  
See also the [http://en.wikipedia.org/wiki/Systemd Wikipedia article].
+
{{Note|1=For a detailed explanation of why Arch moved to ''systemd'', see [https://bbs.archlinux.org/viewtopic.php?pid=1149530#p1149530 this forum post].}}
  
== Things to consider before you switch ==
+
== Basic systemctl usage  ==
  
* It is highly recommended to switch to the new '''initscripts''' configuration system described in the [[rc.conf|rc.conf article]].  Once you have this configuration established, you will have done most of the work needed to make the switch to systemd.
+
The main command used to introspect and control ''systemd'' is ''systemctl''. Some of its uses are examining the system state and managing the system and services. See {{man|1|systemctl}} for more details.
* Do [http://freedesktop.org/wiki/Software/systemd/ some reading] about systemd.
 
* Note the fact that systemd has a '''journal''' system that replaces '''syslog''', although the two can co-exist. See the [[#Journald_in_conjunction_with_a_classic_syslog_daemon|section on the journal]] below.
 
* Do not worry about systemd's plans to replace the functionality of '''cron''', '''acpid''', or '''xinetd'''.  These are not things you need to worry about just yet.  For now, you can continue to use your traditional daemons for these tasks.
 
  
== Installation ==
+
{{Tip|
Systemd can be installed side-by-side with the regular Arch Linux initscripts, and they can be toggled by adding/removing the {{Ic|1=init=/usr/lib/systemd/systemd}} [[kernel parameters]].
+
* You can use all of the following ''systemctl'' commands with the {{ic|-H ''user''@''host''}} switch to control a ''systemd'' instance on a remote machine. This will use [[SSH]] to connect to the remote ''systemd'' instance.
 +
* [[Plasma]] users can install {{AUR|systemd-kcm}} as a graphical frontend for ''systemctl''. After installing the module will be added under ''System administration''.}}
  
=== A pure systemd installation ===
+
=== Analyzing the system state ===
  
# Install {{Pkg|systemd}} from [core].
+
Show '''system status''' using:
# Add {{ic|1=init=/usr/lib/systemd/systemd}} to the [[Kernel parameters|kernel parameters]] in your bootloader.
 
# Create [[#Native systemd configuration files|systemd configuration files]].
 
# [[#Using_Units|Enable services]] with {{ic|systemctl enable ''service''}}. systemd services replace the daemons from {{ic|/etc/rc.conf}}.
 
# Reboot and remove the {{ic|1=init=...}} entry.
 
# Manually remove {{pkg|initscripts}}, and then install {{Pkg|systemd-sysvcompat}}.
 
  
=== A mixed systemd installation ===
+
$ systemctl status
  
# Install {{Pkg|systemd}} from [core]
+
'''List running''' units:
# Add {{ic|1=init=/usr/lib/systemd/systemd}} to the [[Kernel parameters|kernel parameters]] in your bootloader.
 
# We recommend that you use [[#Native systemd configuration files|native systemd configuration files]] instead of Arch's classic configuration files. You can still use {{ic|/etc/rc.conf}} to configure a few variables if the native configuration files do not exist, but support will be dropped in the future.
 
# If you want to keep using syslog log files alongside the systemd journal, follow the instructions described in the [[#Journald_in_conjunction_with_a_classic_syslog_daemon|section on the journal]], below.
 
  
=== Supplementary information ===
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$ systemctl
{{Note|1=In a pure systemd installation, installing {{pkg|systemd-sysvcompat}} removes {{pkg|sysvinit}}, permits the export of {{ic|LANG}} in {{ic|/etc/locale.conf}}, and creates symlinks to halt, reboot, etc. You must manually remove {{pkg|initscripts}} to install {{pkg|systemd-sysvcompat}} [https://bbs.archlinux.org/viewtopic.php?id=148042].}}
+
 
{{Tip|If you have {{ic|quiet}} in your kernel parameters, you should remove it for your first couple of systemd boots, to assist with identifying any issues during boot.}}
+
or:
{{Warning|{{ic|/usr}} must be mounted and available at bootup (this is not particular to systemd). If your {{ic|/usr}} is on a separate partition, you will need to make accommodations to mount it from the initramfs and unmount it from a pivoted root on shutdown. See [[Mkinitcpio#/usr_as_a_separate_partition|the mkinitcpio wiki page]] and [http://www.freedesktop.org/wiki/Software/systemd/separate-usr-is-broken freedesktop.org#separate-usr-is-broken].}}
 
  
== Native systemd configuration files ==
+
$ systemctl list-units
{{Note|You may need to create these files.}}
 
{{Pkg|systemd}} will use {{ic|/etc/rc.conf}} if these files are absent. Note this is temporary and not a long-term solution. It is strongly advised to use the systemd configuration files on any system.
 
=== Hostname ===
 
{{hc|/etc/hostname|myhostname}}
 
  
=== Console and keymap ===
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'''List failed''' units:
The {{ic|/etc/vconsole.conf}} file configures the virtual console, i.e. keyboard mapping and console font.
 
{{hc|/etc/vconsole.conf|<nowiki>
 
KEYMAP=us
 
FONT=lat9w-16
 
FONT_MAP=8859-1_to_uni</nowiki>}}
 
  
For more info see [[Fonts#Console_fonts|Console fonts]] and [[KEYMAP#Keyboard_layouts|Keymap]].
+
$ systemctl --failed
  
=== Locale ===
+
The available unit files can be seen in {{ic|/usr/lib/systemd/system/}} and {{ic|/etc/systemd/system/}} (the latter takes precedence). '''List installed''' unit files with:
Read {{ic|man locale.conf}} for more options:
 
{{hc|/etc/locale.conf|<nowiki>
 
LANG=en_US.UTF-8
 
LC_COLLATE=C</nowiki>}}
 
  
=== Time zone ===
+
$ systemctl list-unit-files
Read {{ic|man 5 timezone}} for more options.
 
{{hc|/etc/timezone|Europe/Minsk}}
 
{{Note|This file does not obviate the need for {{ic|/etc/localtime}}, which is a symbolic link to the desired time zone's zoneinfo file in {{ic|/usr/share/zoneinfo/}}.}}
 
  
=== Hardware clock time ===
+
Show the [[cgroups|cgroup slice]], memory and parent for a PID:
Systemd will use UTC for the hardware clock by default and this is recommended. Dealing with daylight saving time is messy. If the DST changes when your computer is off, your clock will be wrong on next boot ([http://www.cl.cam.ac.uk/~mgk25/mswish/ut-rtc.html there is a lot more to it]). Recent kernels set the system time from the RTC directly on boot without using {{ic|hwclock}}, the kernel will always assume that the RTC is in UTC. This means that if the RTC is in local time, then the system time will first be set up wrongly and then corrected shortly afterwards on every boot. This is possibly the reason for certain weird bugs (time going backwards is rarely a good thing).
 
  
The reason for allowing the RTC to be in local time is to allow dual boot with Windows ([http://blogs.msdn.com/b/oldnewthing/archive/2004/09/02/224672.aspx which uses localtime]). Windows is able to deal with the RTC being in UTC by setting the following DWORD registry key to {{ic|1}}:
+
$ systemctl status ''pid''
{{bc|HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal}}
 
  
{{Warning|On recent systems (Windows 7, Vista SP2) this setting prevents Windows from being able to update the system clock at all, and earlier versions do not work correctly when [http://social.msdn.microsoft.com/forums/en-US/tabletandtouch/thread/0b872d8a-69e9-40a6-a71f-45de90c6e243/ resuming from suspend or hibernate]. In addition, recent systems [http://support.microsoft.com/kb/2687252 may become unresponsive during Daylight Saving Time (DST) changeover] if RealTimeIsUniversal is set.}}
+
=== Using units ===
  
If you run into issues on dual boot with Windows, you can set the hardware clock to local time. Contrary to popular belief, systemd supports this:
+
Units can be, for example, services (''.service''), mount points (''.mount''), devices (''.device'') or sockets (''.socket'').
{{hc|/etc/adjtime|<nowiki>
 
0.0 0.0 0.0
 
0
 
LOCAL</nowiki>}}
 
{{Note|The other parameters are still needed but are ignored by systemd.}}
 
{{Note|It is generally advised to have a [[NTP|Network Time Protocol daemon]] running to keep the hardware clock synchronized with the system time.}}
 
  
=== Kernel modules loaded during boot ===
+
When using ''systemctl'', you generally have to specify the complete name of the unit file, including its suffix, for example {{ic|sshd.socket}}. There are however a few short forms when specifying the unit in the following ''systemctl'' commands:
systemd uses {{ic|/etc/modules-load.d/}} to configure kernel modules to load during boot in a static list. Each configuration file is named in the style of {{ic|/etc/modules-load.d/<program>.conf}}. The configuration files should simply contain a list of kernel module names to load, separated by newlines. Empty lines and lines whose first non-whitespace character is {{ic|#}} or {{ic|;}} are ignored. Example:
 
{{hc|/etc/modules-load.d/virtio-net.conf|<nowiki>
 
# Load virtio-net.ko at boot
 
virtio-net</nowiki>}}
 
See also [[Modprobe#Options]].
 
  
=== Kernel modules blacklist ===
+
* If you do not specify the suffix, systemctl will assume ''.service''. For example, {{ic|netctl}} and {{ic|netctl.service}} are equivalent.
Module blacklisting works the same way as with {{Pkg|initscripts}} since it is actually handled by {{Pkg|kmod}}. See [[Kernel_modules#Blacklisting|Module Blacklisting]] for details.
+
* Mount points will automatically be translated into the appropriate ''.mount'' unit. For example, specifying {{ic|/home}} is equivalent to {{ic|home.mount}}.
 +
* Similar to mount points, devices are automatically translated into the appropriate ''.device'' unit, therefore specifying {{ic|/dev/sda2}} is equivalent to {{ic|dev-sda2.device}}.
  
=== Temporary files ===
+
See {{man|5|systemd.unit}} for details.
Systemd-tmpfiles uses the configuration files in {{ic|/usr/lib/tmpfiles.d/}} and {{ic|/etc/tmpfiles.d/}} to describe the creation, cleaning and removal of volatile and temporary files and directories which usually reside in directories such as {{ic|/run}} or {{ic|/tmp}}. Each configuration file is named in the style of {{ic|/etc/tmpfiles.d/<program>.conf}}. This will also override any files in {{ic|/usr/lib/tmpfiles.d/}} with the same name.
 
  
tmpfiles are usually provided together with service files to create directories which are expected to exist by certain daemons. For example the [[Samba]] daemon expects the directory {{ic|/var/run/samba}} to exist and to have the correct permissions. The corresponding tmpfile looks like this:
+
{{Note|Some unit names contain an {{ic|@}} sign (e.g. {{ic|name@''string''.service}}): this means that they are [http://0pointer.de/blog/projects/instances.html instances] of a ''template'' unit, whose actual file name does not contain the {{ic|''string''}} part (e.g. {{ic|name@.service}}). {{ic|''string''}} is called the ''instance identifier'', and is similar to an argument that is passed to the template unit when called with the ''systemctl'' command: in the unit file it will substitute the {{ic|%i}} specifier.
{{hc|/usr/lib/tmpfiles.d/samba.conf|
 
D /var/run/samba 0755 root root
 
}}
 
  
However, tmpfiles may also be used to write values into certain files on boot. For example, if you use {{ic|/etc/rc.local}} to disable wakeup from USB devices with {{ic|echo USBE > /proc/acpi/wakeup}}, you may use the following tmpfile instead:
+
To be more accurate, ''before'' trying to instantiate the {{ic|name@.suffix}} template unit, ''systemd'' will actually look for a unit with the exact {{ic|name@string.suffix}} file name, although by convention such a "clash" happens rarely, i.e. most unit files containing an {{ic|@}} sign are meant to be templates. Also, if a template unit is called without an instance identifier, it will just fail, since the {{ic|%i}} specifier cannot be substituted.
{{hc|/etc/tmpfiles.d/disable-usb-wake.conf|
 
w /proc/acpi/wakeup - - - - USBE
 
 
}}
 
}}
The tmpfiles method is recommended in this case since systemd doesn't actually support {{ic|/etc/rc.local}}.
 
  
See {{ic|man tmpfiles.d}} for details.
+
{{Tip|
 +
* Most of the following commands also work if multiple units are specified, see {{man|1|systemctl}} for more information.
 +
* The {{ic|--now}} switch can be used in conjunction with {{ic|enable}}, {{ic|disable}}, and {{ic|mask}} to respectively start, stop, or mask the unit ''immediately'' rather than after rebooting.
 +
* A package may offer units for different purposes. If you just installed a package, {{ic|pacman -Qql ''package'' <nowiki>|</nowiki> grep -Fe .service -e .socket}} can be used to check and find them.}}
  
=== Remote filesystem mounts ===
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'''Start''' a unit immediately:
systemd automatically makes sure that remote filesystem mounts like [[NFS]] or [[Samba]] are only started after the network has been set up. Therefore remote filesystem mounts specified in {{ic|/etc/fstab}} should work out of the box.
 
  
You may however want to use [[#Automount|Automount]] for remote filesystem mounts to mount them only upon access. Furthermore you can use the {{ic|1=x-systemd.device-timeout=#}} option in {{ic|/etc/fstab}} to specify a timeout in case the network resource is not available.
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# systemctl start ''unit''
  
See {{ic|man systemd.mount}} for details.
+
'''Stop''' a unit immediately:
  
=== Replacing acpid with systemd ===
+
# systemctl stop ''unit''
systemd can handle some power-related ACPI events. This is configured via the following options in {{ic|/etc/systemd/logind.conf}}:
 
* {{ic|HandlePowerKey}}: Power off the system when the power button is pressed
 
* {{ic|HandleSleepKey}}: Suspend the system when the sleep key is pressed
 
* {{ic|HandleLidSwitch}}: Suspend the system when the laptop lid is closed
 
Depending on the value of these options, these events may for example only be triggered when no user is logged in ({{ic|no-session}}) or when only a single user session is active ({{ic|any-session}}). See {{ic|man logind.conf}} for details.
 
  
These options should not be used on desktop environments like [[GNOME]] and [[Xfce]] since these handle ACPI events by themselves. However, on systems which run no graphical setup or only a simple window manager like [[i3]] or [[awesome]], this may replace the [[acpid]] daemon which is usually used to react to these ACPI events.
+
'''Restart''' a unit:
  
=== Sleep hooks ===
+
# systemctl restart ''unit''
  
Systemd does not use [[pm-utils]] to put the machine to sleep when using {{ic|systemctl suspend}} or {{ic|systemctl hibernate}}, therefore [[pm-utils]] hooks including any [[Pm-utils#Creating_your_own_hooks|custom hooks]] created will not be run.  However, systemd provides a similar mechanism to run custom scripts on these events. Systemd runs all executables in {{ic|/usr/lib/systemd/system-sleep/}} and passes two arguments to each of them:
+
Ask a unit to '''reload''' its configuration:
  
* Argument 1: either {{ic|pre}} or {{ic|post}}, depending on whether the machine is going to sleep or waking up
+
# systemctl reload ''unit''
* Argument 2: either {{ic|suspend}} or {{ic|hibernate}}, depending on what has been invoked
 
  
In contrast to [[pm-utils]], systemd will run these scripts in parallel and not one after another.
+
Show the '''status''' of a unit, including whether it is running or not:
  
The output of your script will be logged by {{ic|systemd-suspend.service}} or {{ic|systemd-hibernate.service}} so you can see its output in the [[Systemd#Systemd Journal|journal]].
+
$ systemctl status ''unit''
  
Note that you can also use {{ic|sleep.target}}, {{ic|suspend.target}} or {{ic|hibernate.target}} to hook units into the sleep state logic instead of using scripts.
+
'''Check''' whether a unit is already enabled or not:
  
See {{ic|man systemd.special}} and {{ic|man systemd-sleep}} for more information.
+
$ systemctl is-enabled ''unit''
  
==== Example ====
+
'''Enable''' a unit to be started on '''bootup''':
{{hc|/usr/lib/systemd/system-sleep/example.sh|<nowiki>
 
case "$1" in
 
  pre )
 
    echo going to $2 ...
 
    ;;
 
  post )
 
    echo waking up from $2 ...
 
    ;;
 
esac</nowiki>}}
 
  
=== Unit ===
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# systemctl enable ''unit''
A unit configuration file encodes information about a service, a socket, a device, a mount point, an automount point, a swap file or partition, a start-up target, a file system path or a timer controlled and supervised by systemd. The syntax is inspired by XDG Desktop Entry Specification .desktop files, which are in turn inspired by Microsoft Windows .ini files. See {{ic|man systemd.unit}} for more info.
 
  
== Systemd commands ==
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'''Enable''' a unit to be started on '''bootup''' and '''Start''' immediately:
  
*{{ic|systemctl}}: used to introspect and control the state of the systemd system and service manager.
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# systemctl enable --now ''unit''
*{{ic|systemd-cgls}}: recursively shows the contents of the selected Linux control group hierarchy in a tree
 
*{{ic|systemadm}}: a graphical frontend for the systemd system and service manager that allows introspection and control of systemd (available via the {{AUR|systemd-ui-git}} package from the [[AUR]]).
 
  
View the man pages for more details.
+
'''Disable''' a unit to not start during bootup:
  
{{Tip|You can use all of the following {{ic|systemctl}} commands with the {{ic|-H <user>@<host>}} switch to control a systemd instance on a remote machine. This will use [[SSH]] to connect to the remote systemd instance.}}
+
# systemctl disable ''unit''
  
=== Analyzing the system state ===
+
'''Mask''' a unit to make it impossible to start it (both manually and as a dependency, which makes masking dangerous):
  
List running units:
+
# systemctl mask ''unit''
  
{{bc|$ systemctl}}
+
'''Unmask''' a unit:
  
or:
+
# systemctl unmask ''unit''
  
{{bc|$ systemctl list-units}}
+
Show the '''manual page''' associated with a unit (this has to be supported by the unit file):
  
List failed units:
+
$ systemctl help ''unit''
  
{{bc|$ systemctl --failed}}
+
'''Reload ''systemd'' ''' manager configuration, scanning for '''new or changed units''':
 +
{{Note|This does not ask the changed units to reload their own configurations. See {{ic|reload}} example above.}}
  
The available unit files can be seen in {{ic|/usr/lib/systemd/system/}} and {{ic|/etc/systemd/system/}} (the latter takes precedence). You can see list installed unit files by:
+
# systemctl daemon-reload
{{bc|$ systemctl list-unit-files}}
 
  
=== Using Units ===
+
=== Power management ===
  
Units can be, for example, services ({{ic|.service}}), mount points ({{ic|.mount}}), devices ({{ic|.device}}) or sockets ({{ic|.socket}}).
+
[[polkit]] is necessary for power management as an unprivileged user. If you are in a local ''systemd-logind'' user session and no other session is active, the following commands will work without root privileges. If not (for example, because another user is logged into a tty), ''systemd'' will automatically ask you for the root password.
When using {{ic|systemctl}}, you generally have to specify the complete name of the unit file, including its suffix, for example {{ic|sshd.socket}}. There are however a few shortforms when specifying the unit in the following {{ic|systemctl}} commands:
 
* If you don't specify the suffix, systemctl will assume {{ic|.service}}. For example, {{ic|netcfg}} and {{ic|netcfg.service}} are treated equivalent. {{Note|This currently does not work with the commands {{ic|enable}} and {{ic|disable}}.}}
 
* Mount points will automatically be translated into the appropriate {{ic|.mount}} unit. For example, specifying {{ic|/home}} is equivalent to {{ic|home.mount}}.
 
* Similiar to mount points, devices are automatically translated into the appropriate {{ic|.device}} unit, therefore specifying {{ic|/dev/sda2}} is equivalent to {{ic|dev-sda2.device}}.
 
  
See {{ic|man systemd.unit}} for details.
+
Shut down and reboot the system:
  
Activate a unit immediately:
+
$ systemctl reboot
  
{{bc|# systemctl start <unit>}}
+
Shut down and power-off the system:
  
Deactivate a unit immediately:
+
$ systemctl poweroff
  
{{bc|# systemctl stop <unit>}}
+
Suspend the system:
  
Restart a unit:
+
$ systemctl suspend
  
{{bc|# systemctl restart <unit>}}
+
Put the system into hibernation:
  
Ask a unit to reload its configuration:
+
$ systemctl hibernate
  
{{bc|# systemctl reload <unit>}}
+
Put the system into hybrid-sleep state (or suspend-to-both):
  
Show the status of a unit, including whether it is running or not:
+
$ systemctl hybrid-sleep
  
{{bc|$ systemctl status <unit>}}
+
== Writing unit files ==
  
Check whether a unit is already enabled or not:
+
The syntax of ''systemd'''s [https://www.freedesktop.org/software/systemd/man/systemd.unit.html unit files] is inspired by XDG Desktop Entry Specification ''.desktop'' files, which are in turn inspired by Microsoft Windows ''.ini'' files. Unit files are loaded from multiple locations (to see the full list, run {{ic|1=systemctl show --property=UnitPath}}), but the main ones are (listed from lowest to highest precedence):
  
{{bc|$ systemctl is-enabled <unit>}}
+
* {{ic|/usr/lib/systemd/system/}}: units provided by installed packages
 +
* {{ic|/etc/systemd/system/}}: units installed by the system administrator
  
Enable a unit to be started on bootup:
+
{{Note|
 +
* The load paths are completely different when running ''systemd'' in [[systemd/User#How it works|user mode]].
 +
* systemd unit names may only contain ASCII alphanumeric characters, underscores and periods. All other characters must be replaced by C-style "\x2d" escapes, or employ their predefined semantics ('@', '-'). See {{man|5|systemd.unit}} and {{man|1|systemd-escape}} for more information.}}
  
{{bc|# systemctl enable <unit>}}
+
Look at the units installed by your packages for examples, as well as the [https://www.freedesktop.org/software/systemd/man/systemd.service.html#Examples annotated example section] of {{man|5|systemd.service}}.
  
{{Note| If services do not have an Install section, it usually means they are called automatically by other services. But if you need to install them manually, use the following command, replacing ''foo'' with the name of the service.
+
{{Tip|Comments prepended with {{ic|#}} may be used in unit-files as well, but only in new lines. Do not use end-line comments after ''systemd'' parameters or the unit will fail to activate.}}
  
{{bc|# ln -s /usr/lib/systemd/system/''foo''.service /etc/systemd/system/graphical.target.wants/}}
+
=== Handling dependencies ===
  
}}
+
With ''systemd'', dependencies can be resolved by designing the unit files correctly. The most typical case is that the unit ''A'' requires the unit ''B'' to be running before ''A'' is started. In that case add {{ic|1=Requires=''B''}} and {{ic|1=After=''B''}} to the {{ic|[Unit]}} section of ''A''. If the dependency is optional, add {{ic|1=Wants=''B''}} and {{ic|1=After=''B''}} instead. Note that {{ic|1=Wants=}} and {{ic|1=Requires=}} do not imply {{ic|1=After=}}, meaning that if {{ic|1=After=}} is not specified, the two units will be started in parallel.
  
Disable a unit to not start during bootup:
+
Dependencies are typically placed on services and not on [[#Targets]]. For example, {{ic|network.target}} is pulled in by whatever service configures your network interfaces, therefore ordering your custom unit after it is sufficient since {{ic|network.target}} is started anyway.
  
{{bc|# systemctl disable <unit>}}
+
=== Service types ===
  
Show the manual page associated with a unit (this has to be supported by the unit file):
+
There are several different start-up types to consider when writing a custom service file. This is set with the {{ic|1=Type=}} parameter in the {{ic|[Service]}} section:
  
{{bc|$ systemctl help <unit>}}
+
* {{ic|1=Type=simple}} (default): ''systemd'' considers the service to be started up immediately. The process must not fork. Do not use this type if other services need to be ordered on this service, unless it is socket activated.
 +
* {{ic|1=Type=forking}}: ''systemd'' considers the service started up once the process forks and the parent has exited. For classic daemons use this type unless you know that it is not necessary. You should specify {{ic|1=PIDFile=}} as well so ''systemd'' can keep track of the main process.
 +
* {{ic|1=Type=oneshot}}: this is useful for scripts that do a single job and then exit. You may want to set {{ic|1=RemainAfterExit=yes}} as well so that ''systemd'' still considers the service as active after the process has exited.
 +
* {{ic|1=Type=notify}}: identical to {{ic|1=Type=simple}}, but with the stipulation that the daemon will send a signal to ''systemd'' when it is ready. The reference implementation for this notification is provided by ''libsystemd-daemon.so''.
 +
* {{ic|1=Type=dbus}}: the service is considered ready when the specified {{ic|BusName}} appears on DBus's system bus.
 +
* {{ic|1=Type=idle}}: ''systemd'' will delay execution of the service binary until all jobs are dispatched. Other than that behavior is very similar to {{ic|1=Type=simple}}.
  
=== Power Management ===
+
See the [https://www.freedesktop.org/software/systemd/man/systemd.service.html#Type= systemd.service(5)] man page for a more detailed explanation of the {{ic|Type}} values.
  
If you are in a local ConsoleKit user session and no other session is active, the following commands will work without root privileges. If not (for example, because another user is logged into a tty), systemd will automatically ask you for the root password.
+
=== Editing provided units ===
  
Shut down and reboot the system:
+
{{Style|Should be renamed to more descriptive ''Modifying provided units''.|talk=Talk:Edit#Deprecation}}
  
{{bc|$ systemctl reboot}}
+
To avoid conflicts with pacman, unit files provided by packages should not be directly edited. There are two safe ways to modify a unit without touching the original file: create a new unit file which [[#Replacement unit files|overrides the original unit]] or create [[#Drop-in files|drop-in snippets]] which are applied on top of the original unit. For both methods, you must reload the unit afterwards to apply your changes. This can be done either by editing the unit with {{ic|systemctl edit}} (which reloads the unit automatically) or by reloading all units with:
  
Shut down and power-off the system:
+
# systemctl daemon-reload
  
{{bc|$ systemctl poweroff}}
+
{{Tip|
 +
* You can use ''systemd-delta'' to see which unit files have been overridden or extended and what exactly has been changed.
 +
* Use {{ic|systemctl cat ''unit''}} to view the content of a unit file and all associated drop-in snippets.
 +
}}
  
Shut down and halt the system:
+
==== Replacement unit files ====
  
{{bc|$ systemctl halt}}
+
To replace the unit file {{ic|/usr/lib/systemd/system/''unit''}}, create the file {{ic|/etc/systemd/system/''unit''}} and ''reenable'' the unit to update the symlinks:
  
Suspend the system:
+
# systemctl reenable ''unit''
  
{{bc|$ systemctl suspend}}
+
Alternatively, run:
  
Hibernate the system:
+
# systemctl edit --full ''unit''
  
{{bc|$ systemctl hibernate}}
+
This opens {{ic|/etc/systemd/system/''unit''}} in your editor (copying the installed version if it does not exist yet) and automatically reloads it when you finish editing.
  
== Runlevels/targets ==
+
{{Note|The replacement units will keep on being used even if Pacman updates the original units in the future. This method makes system maintenance more difficult and therefore the next approach is preferred.}}
Runlevels is a legacy concept in systemd. Systemd uses ''targets'' which serve a similar purpose as runlevels but act a little different. Each ''target'' is named instead of numbered and is intended to serve a specific purpose with the possibility of having multiple ones active at the same time. Some ''targets'' are implemented by inheriting all of the services of another ''target'' and adding additional services to it. There are systemd ''target''s that mimic the common SystemVinit runlevels so you can still switch ''target''s using the familiar {{ic|telinit RUNLEVEL}} command.
 
  
=== Get current runlevel/targets ===
+
==== Drop-in files ====
The following should be used under systemd instead of {{ic|runlevel}}:
 
{{bc|1=# systemctl list-units --type=target}}
 
  
=== Create custom target ===
+
To create drop-in files for the unit file {{ic|/usr/lib/systemd/system/''unit''}}, create the directory {{ic|/etc/systemd/system/''unit''.d/}} and place ''.conf'' files there to override or add new options. ''systemd'' will parse and apply these files on top of the original unit.
The runlevels that are assigned a specific purpose on vanilla Fedora installs; 0, 1, 3, 5, and 6; have a 1:1 mapping with a specific systemd ''target''. Unfortunately, there is no good way to do the same for the user-defined runlevels like 2 and 4. If you make use of those it is suggested that you make a new named systemd ''target'' as {{ic|/etc/systemd/system/<your target>}} that takes one of the existing runlevels as a base (you can look at {{ic|/usr/lib/systemd/system/graphical.target}} as an example), make a directory {{ic|/etc/systemd/system/<your target>.wants}}, and then symlink the additional services from {{ic|/usr/lib/systemd/system/}} that you wish to enable.
 
  
=== Targets table ===
+
The easiest way to do this is to run:
{| border="1"
 
!SysV Runlevel!!Systemd Target!!Notes
 
|-
 
| 0 || runlevel0.target, poweroff.target || Halt the system.
 
|-
 
| 1, s, single || runlevel1.target, rescue.target || Single user mode.
 
|-
 
| 2, 4 || runlevel2.target, runlevel4.target, multi-user.target || User-defined/Site-specific runlevels. By default, identical to 3.
 
|-
 
| 3 || runlevel3.target, multi-user.target || Multi-user, non-graphical. Users can usually login via multiple consoles or via the network.
 
|-
 
| 5 || runlevel5.target, graphical.target || Multi-user, graphical. Usually has all the services of runlevel 3 plus a graphical login.
 
|-
 
| 6 || runlevel6.target, reboot.target || Reboot
 
|-
 
| emergency || emergency.target || Emergency shell
 
|-
 
|}
 
  
=== Change current runlevels ===
+
# systemctl edit ''unit''
In systemd runlevels are exposed via "target units". You can change them like this:
 
{{bc|# systemctl isolate graphical.target}}
 
This will only change the current runlevel, and has no effect on the next boot. This is equivalent to commands such as {{ic|telinit 3}} or {{ic|telinit 5}} in Sysvinit.
 
  
=== Change default runlevel/target to boot into ===
+
This opens the file {{ic|/etc/systemd/system/''unit''.d/override.conf}} in your text editor (creating it if necessary) and automatically reloads the unit when you are done editing.
The standard target is {{ic|default.target}}, which is aliased by default to {{ic|graphical.target}} (which roughly corresponds to the old runlevel 5). To change the default target at boot-time, append one of the following kernel parameters to your bootloader:
 
* {{ic|1=systemd.unit=multi-user.target}} (which roughly corresponds to the old runlevel 3),
 
* {{ic|1=systemd.unit=rescue.target}} (which roughly corresponds to the old runlevel 1).
 
  
Alternatively, you may leave the bootloader alone and change {{ic|default.target}}. This can be done using {{ic|systemctl}}:
+
{{Note|Not all keys can be overridden with drop-in files. For example, for changing {{ic|1=Conflicts=}} a replacement file [https://lists.freedesktop.org/archives/systemd-devel/2017-June/038976.html is necessary].}}
{{bc|# systemctl enable multi-user.target}}
 
  
The effect of this command is outputted by {{ic|systemctl}}; a symlink to the new default target is made at {{ic|/etc/systemd/system/default.target}}. This works if, and only if:
+
==== Revert to vendor version ====
[Install]
 
Alias=default.target
 
is in the target's configuration file. Currently, {{ic|multi-user.target}} and {{ic|graphical.target}} both have it.
 
  
== Running DEs under systemd ==
+
To revert any changes to a unit made using {{ic|systemctl edit}} do:
  
=== Using display manager ===
+
# systemctl revert ''unit''
To enable graphical login, run your preferred [[Display Manager]] daemon (e.g. [[KDM]]). At the moment, service files exist for [[GDM]], [[KDM]], [[SLiM]], [[XDM]] and [[LXDM]].
 
  
{{bc|# systemctl enable kdm.service}}
+
==== Examples ====
  
This should work out of the box. If not, you might have a {{ic|default.target}} set manually or from a older install:
+
For example, if you simply want to add an additional dependency to a unit, you may create the following file:
  
{{hc|# ls -l /etc/systemd/system/default.target|/etc/systemd/system/default.target -> /usr/lib/systemd/system/graphical.target}}
+
{{hc|/etc/systemd/system/''unit''.d/customdependency.conf|2=
 +
[Unit]
 +
Requires=''new dependency''
 +
After=''new dependency''
 +
}}
  
Simply delete the symlink and systemd will use its stock {{ic|default.target}} (i.e. {{ic|graphical.target}}).
+
As another example, in order to replace the {{ic|ExecStart}} directive for a unit that is not of type {{ic|oneshot}}, create the following file:
  
{{bc|# rm /etc/systemd/system/default.target}}
+
{{hc|/etc/systemd/system/''unit''.d/customexec.conf|2=
 +
[Service]
 +
ExecStart=
 +
ExecStart=''new command''
 +
}}
  
=== Using service file ===
+
Note how {{ic|ExecStart}} must be cleared before being re-assigned [https://bugzilla.redhat.com/show_bug.cgi?id=756787#c9]. The same holds for every item that can be specified multiple times, e.g. {{ic|OnCalendar}} for timers.
{{Note|Using this method there will be no PAM session created for your user. Therefore ConsoleKit (which gives you access to shutdown/reboot, audio devices etc.) will not work properly. For the recommended way, see: [[Automatic_login_to_virtual_console#With_systemd]].}}
 
If you are only looking for a simple way to start X directly without a display manager, you can create a service file similar to this:
 
  
{{hc|/etc/systemd/system/graphical.target.wants/xinit.service|<nowiki>
+
One more example to automatically restart a service:
[Unit]
 
Description=Direct login to X
 
After=systemd-user-sessions.service
 
  
 +
{{hc|/etc/systemd/system/''unit''.d/restart.conf|2=
 
[Service]
 
[Service]
ExecStart=/bin/su <username> -l -c "/bin/bash --login -c xinit"
+
Restart=always
 +
RestartSec=30
 +
}}
  
[Install]
+
== Targets ==
WantedBy=graphical.target
 
</nowiki>}}
 
  
== Systemd Journal ==
+
{{Style|Unclear description, copy-pasted content (explicitly mentions "Fedora").|section=Make section "Targets" more clearly}}
Since version 38 systemd has an own logging system, the journal.
 
  
By default, running a syslog daemon is no longer required. To read the log, use:
+
''systemd'' uses ''targets'' to group units together via dependencies and as standardized synchronization points. They serve a similar purpose as [[wikipedia:Runlevel|runlevels]] but act a little different. Each ''target'' is named instead of numbered and is intended to serve a specific purpose with the possibility of having multiple ones active at the same time. Some ''target''s are implemented by inheriting all of the services of another ''target'' and adding additional services to it. There are ''systemd'' ''target''s that mimic the common SystemVinit runlevels so you can still switch ''target''s using the familiar {{ic|telinit RUNLEVEL}} command.
{{bc|# journalctl}}
 
The journal writes to {{ic|/run/systemd/journal}}, meaning logs will be lost on reboot. For non-volatile logs, create {{ic|/var/log/journal/}}:
 
{{bc|# mkdir /var/log/journal/}}
 
  
=== Filtering output ===
+
=== Get current targets ===
  
{{ic|journalctl}} allows you to filter the output by specific fields.
+
The following should be used under ''systemd'' instead of running {{ic|runlevel}}:
  
Examples:
+
$ systemctl list-units --type=target
  
Show all messages by a specific executable:
+
=== Create custom target ===
{{bc|# journalctl /usr/lib/systemd/systemd}}
 
  
Show all messages by a specific process:
+
The runlevels that held a defined meaning under sysvinit (i.e., 0, 1, 3, 5, and 6); have a 1:1 mapping with a specific ''systemd'' ''target''. Unfortunately, there is no good way to do the same for the user-defined runlevels like 2 and 4. If you make use of those it is suggested that you make a new named ''systemd'' ''target'' as {{ic|/etc/systemd/system/''your target''}} that takes one of the existing runlevels as a base (you can look at {{ic|/usr/lib/systemd/system/graphical.target}} as an example), make a directory {{ic|/etc/systemd/system/''your target''.wants}}, and then symlink the additional services from {{ic|/usr/lib/systemd/system/}} that you wish to enable.
{{bc|1=# journalctl _PID=1}}
+
 
 +
=== Mapping between SysV runlevels and systemd targets ===
 +
 
 +
{| class="wikitable"
 +
! SysV Runlevel !! systemd Target !! Notes
 +
|-
 +
| 0 || runlevel0.target, poweroff.target || Halt the system.
 +
|-
 +
| 1, s, single || runlevel1.target, rescue.target || Single user mode.
 +
|-
 +
| 2, 4 || runlevel2.target, runlevel4.target, multi-user.target || User-defined/Site-specific runlevels. By default, identical to 3.
 +
|-
 +
| 3 || runlevel3.target, multi-user.target || Multi-user, non-graphical. Users can usually login via multiple consoles or via the network.
 +
|-
 +
| 5 || runlevel5.target, graphical.target || Multi-user, graphical. Usually has all the services of runlevel 3 plus a graphical login.
 +
|-
 +
| 6 || runlevel6.target, reboot.target || Reboot
 +
|-
 +
| emergency || emergency.target || Emergency shell
 +
|-
 +
|}
  
Show all messages by a specific unit:
+
=== Change current target ===
{{bc|1=# journalctl _SYSTEMD_UNIT=netcfg.service}}
 
  
See {{ic|man journalctl}} and {{ic|systemd.journal-fields}} for details.
+
In ''systemd'' targets are exposed via ''target units''. You can change them like this:
  
=== Journal size limit ===
+
# systemctl isolate graphical.target
  
If the journal is made non-volatile, its size limit is set to a default value of 10% of the size of the respective file system. E.g. with {{ic|/var/log/journal}} located on a 50 GiB root partition this would lead to 5 GiB of journal data. The maximum size of the persistent journal can be controlled by {{ic|SystemMaxUse}} in {{ic|/etc/systemd/journald.conf}}, so to limit it for example to 50 MiB uncomment and edit the corresponding line to:
+
This will only change the current target, and has no effect on the next boot. This is equivalent to commands such as {{ic|telinit 3}} or {{ic|telinit 5}} in Sysvinit.
{{bc|1=SystemMaxUse=50M}}
 
Refer to {{ic|man journald.conf}} for more info.
 
  
===Journald in conjunction with a classic syslog daemon===
+
=== Change default target to boot into ===
Compatibility with classic syslog implementations is provided via a
 
socket {{ic|/run/systemd/journal/syslog}}, to which all messages are forwarded.
 
To make the syslog daemon work with the journal, it has to bind to this socket instead of {{ic|/dev/log}} ([http://lwn.net/Articles/474968/ official announcement]). For syslog-ng, change the {{ic|source src}} section in {{ic|/etc/syslog-ng/syslog-ng.conf}} to:
 
{{bc|<nowiki>
 
source src {
 
    unix-dgram("/run/systemd/journal/syslog");
 
    internal();
 
    file("/proc/kmsg");
 
};</nowiki>}}
 
  
and enable syslog-ng:
+
The standard target is {{ic|default.target}}, which is a symlink to {{ic|graphical.target}}. This roughly corresponds to the old runlevel 5.
{{bc|# systemctl enable syslog-ng.service}}
 
  
== Network ==
+
To verify the current target with ''systemctl'':
=== Dynamic (DHCP) with dhcpcd ===
 
If you simply want to use DHCP for your Ethernet connection, you can use {{ic|dhcpcd@.service}} (provided by the {{Pkg|dhcpcd}} package).
 
To enable DHCP for {{ic|eth0}}, simply use:
 
# systemctl start dhcpcd@eth0.service
 
  
You can enable the service to automatically start at boot with:
+
  $ systemctl get-default
  # systemctl enable dhcpcd@eth0.service
 
  
=== Other configurations ===
+
To change the default target to boot into, change the {{ic|default.target}} symlink. With ''systemctl'':
For static, wireless or advanced network configuration like bridging you can use [[Netcfg#systemd_support|netcfg]] or [[NetworkManager#Enable_NetworkManager_under_Native_systemd_system|NetworkManager]] which both provide systemd service files.
 
{{Note|If you want to use netcfg, networkmanager or another software for managing the network you don't need to start/enable dhcpcd as seen on the previous paragraph.}}
 
  
If you need a static Ethernet configuration, but don't want to use [[netcfg]], there is a custom service file available on the [[Systemd/Services#Network|Systemd/Services page]].
+
{{hc|1=# systemctl set-default multi-user.target|2=
 +
Removed /etc/systemd/system/default.target.
 +
Created symlink /etc/systemd/system/default.target -> /usr/lib/systemd/system/multi-user.target.}}
  
== Arch integration ==
+
Alternatively, append one of the following [[kernel parameters]] to your bootloader:
=== Initscripts emulation ===
 
Integration with Arch's classic configuration is provided by the {{Pkg|initscripts}} package. This is simply meant as a transitional measure to ease users' move to systemd.
 
  
{{Note|{{ic|/etc/inittab}} is not used at all.}}
+
* {{ic|1=systemd.unit=multi-user.target}} (which roughly corresponds to the old runlevel 3),
 +
* {{ic|1=systemd.unit=rescue.target}} (which roughly corresponds to the old runlevel 1).
  
If you disabled {{keypress|Ctrl+Alt+Del}} to reboot in {{ic|/etc/inittab}}, you will have to reconfigure this setting for systemd by running {{ic|systemctl mask ctrl-alt-del.target}} as root.
+
=== Default target order ===
  
==== rc.conf ====
+
Systemd chooses the {{ic|default.target}} according to the following order:
Some variables in {{ic|/etc/rc.conf}} are respected by this glue work. For a pure systemd setup, it is recommended to use the [[Systemd#Native_systemd_configuration_files|native systemd configuration files]] which will take precedence over {{ic|/etc/rc.conf}}.
 
  
Supported variables:
+
# Kernel parameter shown above
* {{ic|LOCALE}}
+
# Symlink of {{ic|/etc/systemd/system/default.target}}
* {{ic|KEYMAP}}
+
# Symlink of {{ic|/usr/lib/systemd/system/default.target}}
* {{ic|CONSOLEFONT}}
 
* {{ic|CONSOLEMAP}}
 
* {{ic|HOSTNAME}}
 
* {{ic|DAEMONS}}
 
  
Not supported variables and systemd configuration:
+
== Temporary files ==
* {{ic|TIMEZONE}}: Please symlink {{Ic|/etc/localtime}} to your zoneinfo file manually.
 
* {{ic|HARDWARECLOCK}}: See [[Systemd#Hardware clock time|Hardware clock time]].
 
* {{ic|USELVM}}: use {{ic|lvm.service}} provided by {{Pkg|lvm2}} instead.
 
* {{ic|USECOLOR}}
 
* {{ic|MODULES}}
 
  
=== Total conversion to native systemd ===
+
"''systemd-tmpfiles'' creates, deletes and cleans up volatile and temporary files and directories." It reads configuration files in {{ic|/etc/tmpfiles.d/}} and {{ic|/usr/lib/tmpfiles.d/}} to discover which actions to perform. Configuration files in the former directory take precedence over those in the latter directory.
{{Note|This is the preferred method, where the system does not rely on {{ic|rc.conf}} centralised configuration anymore, but uses native systemd configuration files.}}
 
  
Follow system configuration as explained in [[#Native_systemd_configuration_files]]. Each file replaces one section of {{ic|/etc/rc.conf}} as shown in that table:
+
Configuration files are usually provided together with service files, and they are named in the style of {{ic|/usr/lib/tmpfiles.d/''program''.conf}}. For example, the [[Samba]] daemon expects the directory {{ic|/run/samba}} to exist and to have the correct permissions. Therefore, the {{Pkg|samba}} package ships with this configuration:
{| class="wikitable"
 
|-
 
! scope="col"| Configuration
 
! scope="col"| Configuration file(s)
 
! scope="col"| Legacy {{ic|/etc/rc.conf}} section
 
|-
 
| align="center"|Hostname
 
| align="left"|{{ic|/etc/hostname}}
 
{{ic|/etc/hosts}}
 
| align="center"|{{ic|NETWORKING}}
 
|-
 
| align="center"|Console fonts and Keymap
 
| align="left"|{{ic|/etc/vconsole.conf}}
 
| align="center"|{{ic|LOCALIZATION}}
 
|-
 
| align="center"|Locale
 
| align="left"|{{ic|/etc/locale.conf}}
 
{{ic|/etc/locale.gen}}
 
| align="center"|{{ic|LOCALIZATION}}
 
|-
 
| align="center"|Time zone
 
| align="left"|{{ic|/etc/timezone}}
 
{{ic|/etc/localtime}}
 
| align="center"|{{ic|LOCALIZATION}}
 
|-
 
| align="center"|Hardware clock
 
| align="left"|{{ic|/etc/adjtime}}
 
| align="center"|{{ic|LOCALIZATION}}
 
|-
 
| align="center"|Kernel modules
 
| align="left"|{{ic|/etc/modules-load.d/}}
 
| align="center"|{{ic|HARDWARE}}
 
|}
 
  
For legacy purposes, the '''DAEMONS''' section in {{ic|/etc/rc.conf}} is still compatible with systemd and can be used to start services at boot, even with a "pure" systemd service management. Alternatively, you may remove the {{ic|/etc/rc.conf}} file entirely and enable services in systemd. For each {{ic|<service_name>}} in the '''DAEMONS''' array in {{ic|/etc/rc.conf}}, type:
+
{{hc|/usr/lib/tmpfiles.d/samba.conf|
# systemctl enable <service_name>.service
+
D /run/samba 0755 root root}}
{{Tip|For a list of commonly used daemons with their initscripts and systemd equivalents, see [[Daemon#List_of_Daemons|this table]].}}
 
  
If {{ic|<service_name>.service}} does not exist:
+
Configuration files may also be used to write values into certain files on boot. For example, if you used {{ic|/etc/rc.local}} to disable wakeup from USB devices with {{ic|echo USBE > /proc/acpi/wakeup}}, you may use the following tmpfile instead:
* the service file may not be available for systemd. In that case, you'll need to keep {{ic|rc.conf}} to start the service during boot up.
 
* systemd may name services differently, e.g. {{ic|cronie.service}} replaces {{ic|crond}} init daemon; {{ic|alsa-store.service}} and {{ic|alsa-restore.service}} replace the {{ic|alsa}} init daemon. Another important instance is the {{ic|network}} daemon, which is replaced with another set of service files (see [[#Network]] for more details.)
 
{{Tip|You may look inside a package that contains daemon start scripts for service names. For instance:
 
$ pacman -Ql cronie
 
[...]
 
cronie /etc/rc.d/crond                            #<-- daemon initscript listed in the DAEMONS array (unused in a "pure" systemd configuration)
 
[...]
 
cronie /usr/lib/systemd/system/cronie.service    #<-- corresponding systemd daemon service
 
[...]
 
}}
 
* systemd will automatically handle the start order of these daemons.
 
* some services do not need to be explicitly enabled by the user. For instance, {{ic|dbus.service}} will automatically be enabled when {{ic|dbus-core}} is installed. Check the list of available services and their state using the {{ic|systemctl}} command.
 
  
==Writing custom .service files==
+
{{hc|/etc/tmpfiles.d/disable-usb-wake.conf|
===Handling dependencies===
+
#    Path                  Mode UID  GID  Age Argument
With systemd dependencies can be resolved by designing the unit files correctly. The most typical case is that the unit {{ic|A}} requires the unit {{ic|B}} to be running before {{ic|A}} is started. In that case add {{ic|1=Requires=B}} and {{ic|1=After=B}} to the {{ic|[Unit]}} section of {{ic|A}}. If the dependency is optional, add {{ic|1=Wants=B}} and {{ic|1=After=B}} instead. Note that {{ic|1=Wants=}} and {{ic|1=Requires=}} do not imply {{ic|1=After=}}, meaning that if {{ic|1=After=}} is not specified, the two units will be started in parallel.
+
w    /proc/acpi/wakeup    -    -    -    -  USBE}}
  
Dependencies are typically placed on services and not on targets. For example, {{ic|network.target}} is pulled in by whatever service configures your network interfaces, therefore ordering your custom unit after it is sufficient since {{ic|network.target}} is started anyway.
+
See the {{man|8|systemd-tmpfiles}} and {{man|5|tmpfiles.d}} man pages for details.
  
===Type===
+
{{Note|This method may not work to set options in {{ic|/sys}} since the ''systemd-tmpfiles-setup'' service may run before the appropriate device modules is loaded. In this case you could check whether the module has a parameter for the option you want to set with {{ic|modinfo ''module''}} and set this option with a [[Kernel modules#Setting module options|config file in /etc/modprobe.d]]. Otherwise you will have to write a [[Udev#About_udev_rules|udev rule]] to set the appropriate attribute as soon as the device appears.}}
There are several different start-up types to consider when writing a custom service file. This is set with the {{ic|1=Type=}} parameter in the {{ic|[Service]}} section. See {{ic|man systemd.service}} for a more detailed explanation.
 
* {{ic|1=Type=simple}}: systemd considers the daemon to be started up immediately. The process must not fork. Do not use this type if other services need to be ordered on this service, unless it is socket activated.
 
* {{ic|1=Type=forking}}: systemd considers the daemon started up once the process forks and the parent has exited. For classic daemons use this type unless you know that it is not necessary, as most daemons use double-forking to signal that they are ready. You should specify {{ic|1=PIDFile=}} as well so systemd can keep track of the main process.
 
* {{ic|1=Type=oneshot}}: This is useful for scripts that do a single job and then exit. You may want to set {{ic|1=RemainAfterExit=}} as well so that systemd still considers the service as active after the process has exited.
 
* {{ic|1=Type=notify}}: Identical to {{ic|1=Type=simple}}, but with the stipulation that the daemon will send a signal to systemd when it is ready. This requires systemd-specific code provided by {{ic|libsystemd-daemon.so}}.
 
* {{ic|1=Type=dbus}}: The daemon is considered ready when the specified {{ic|BusName}} appears on DBus's system bus.
 
  
===Replacing provided unit files===
+
== Timers ==
The unit files in {{ic|/etc/systemd/system/}} take precedence over the ones in {{ic|/usr/lib/systemd/system/}}.
 
To make your own version of a unit (which will not be destroyed by an upgrade), copy the old unit file from {{ic|/usr/lib/}} to {{ic|/etc/}} and make your changes there. Alternatively you can use {{ic|.include}} to parse an existing service file and then override or add new options. For example, if you simply want to add an additional dependency to a service file, you may use:
 
{{hc|/etc/systemd/system/<service-name>.service|
 
<nowiki>
 
.include /usr/lib/systemd/system/<service-name>.service
 
  
[Unit]
+
A timer is a unit configuration file whose name ends with ''.timer'' and encodes information about a timer controlled and supervised by ''systemd'', for timer-based activation. See [[systemd/Timers]].
Requires=<new dependency>
 
After=<new dependency>
 
</nowiki>}}
 
Then run the following for your changes to take effect:
 
# systemctl reenable <unit>
 
# systemctl restart <unit>
 
{{Tip|You can use {{ic|systemd-delta}} to see which unit files have been overridden and what exactly has been changed.}}
 
  
===Syntax highlighting for systemd unit files within Vim===
+
{{Note|Timers can replace [[cron]] functionality to a great extent. See [[systemd/Timers#As a cron replacement]].}}
Syntax highlighting for systemd unit files within [[Vim]] can be enabled by installing {{AUR|vim-systemd}} from the [[Arch User Repository|AUR]].
 
  
== FAQ ==
+
== Mounting ==
For an up-to-date list of known issues, look at the upstream [http://cgit.freedesktop.org/systemd/systemd/tree/TODO TODO].
 
  
{{FAQ
+
''systemd'' is in charge of mounting the partitions and filesystems specified in {{ic|/etc/fstab}}. The {{man|8|systemd-fstab-generator}} translates all the entries in {{ic|/etc/fstab}} into systemd units, this is performed at boot time and whenever the configuration of the system manager is reloaded.
|question=Why are my console fonts ugly?
 
|answer=If no font is set in {{ic|/etc/vconsole.conf}} (or alternatively {{ic|/etc/rc.conf}}), then a standard font will be used. The standard font is chosen due to it supporting a wide range of character sets. Set your preferred font to fix the issue.}}
 
  
{{FAQ
+
''systemd'' extends the usual [[fstab]] capabilities and offers additional mount options. These affect the dependencies of the mount unit, they can for example ensure that a mount is performed only once the network is up or only once another partition is mounted. The full list of specific ''systemd'' mount options, typically prefixed with {{ic|x-systemd.}}, is detailed in {{man|5|systemd.mount|FSTAB}}.
|question=Why do I get log messages on my console?
 
|answer=You must set the kernel loglevel yourself. Historically, {{ic|/etc/rc.sysinit}} did this for us and set dmesg loglevel to {{ic|3}}, which was a reasonably quiet loglevel. Either add {{ic|1=loglevel=3}} or {{ic|quiet}} to your [[kernel parameters]].}}
 
  
{{FAQ
+
An example of these mount options in the context of ''automounting'', which means mounting only when the resource is required rather than automatically at boot time, is provided in [[fstab#Automount with systemd]].
|question=How do I change the number of gettys running by default?
 
|answer=To add another getty, simply place another symlink for instantiating another getty in the {{ic|/etc/systemd/system/getty.target.wants/}} directory:
 
  
{{bc|<nowiki># ln -sf /usr/lib/systemd/system/getty@.service /etc/systemd/system/getty.target.wants/getty@tty9.service
+
=== GPT partition automounting ===
# systemctl daemon-reload
 
# systemctl start getty@tty9.service</nowiki>}}
 
  
To remove a getty, simply remove the getty symlinks you want to get rid of in the {{ic|/etc/systemd/system/getty.target.wants/}} directory:
+
On a [[GPT]] partitioned disk {{man|8|systemd-gpt-auto-generator}} will mount partitions following the [https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/ Discoverable Partitions Specification], thus they can be omitted from {{ic|fstab}}.
  
{{bc|<nowiki># rm /etc/systemd/system/getty.target.wants/getty@tty5.service /etc/systemd/system/getty.target.wants/getty@tty6.service
+
The automounting for a partition can be disabled by changing the partition's [[Wikipedia:GUID Partition Table#Partition type GUIDs|type GUID]] or setting the partition attribute bit 63 "do not automount", see [[gdisk#Prevent GPT partition automounting]].
# systemctl daemon-reload
 
# systemctl stop getty@tty5.service getty@tty6.service</nowiki>}}
 
  
systemd does not use the {{ic|/etc/inittab}} file.
+
== Tips and tricks ==
  
{{Note|As of systemd 30, only 1 getty will be launched by default. If you switch to another tty, a getty will be launched there (socket-activation style). You can still force additional agetty processes to start using the above methods.}}}}
+
=== Running services after the network is up ===
  
{{FAQ
+
To delay a service after the network is up, include the following dependencies in the ''.service'' file:
|question=How do I get more verbose output during boot?
 
|answer=If you see no output at all in console after the initram message, this means you have the {{ic|quiet}} parameter in your kernel line. It's best to remove it, at least the first time you boot with systemd, to see if everything is ok. Then, You will see a list {{ic|[ OK ]}} in green or {{ic|[ FAILED ]}} in red.
 
  
Any messages are logged to the system log and if you want to find out about the status of your system run {{ic|systemctl}} (no root privileges required) or look at the boot/system log with {{ic|journalctl}}.
+
{{hc|/etc/systemd/system/''foo''.service|2=
 +
[Unit]
 +
...
 +
'''Wants=network-online.target'''
 +
'''After=network-online.target'''
 +
...
 
}}
 
}}
  
{{FAQ
+
The network wait service of the particular application that manages the network, must also be enabled so that {{ic|network-online.target}} properly reflects the network status.
|question=How do I avoid clearing the console after boot?
+
* For the ones using [[NetworkManager]], [[enable]] {{ic|NetworkManager-wait-online.service}}.
|answer=Create a custom {{ic|getty@tty1.service}} file by copying {{ic|/usr/lib/systemd/system/getty@.service}} to {{ic|/etc/systemd/system/getty.target.wants/getty@tty1.service}} and change {{ic|TTYVTDisallocate}} to {{ic|no}}.
+
* In the case of [[netctl]], enable the {{ic|netctl-wait-online.service}}.
}}
+
* If using [[systemd-networkd]], {{ic|systemd-networkd-wait-online.service}} is by default enabled automatically whenever {{ic|systemd-networkd.service}} has been enabled; check this is the case with {{ic|systemctl is-enabled systemd-networkd-wait-online.service}}, there is no other action needed.
 +
 
 +
For more detailed explanations see [https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/ Running services after the network is up] in the systemd wiki.
  
{{FAQ
+
=== Enable installed units by default ===
|question=What kernel options do I need to enable in my kernel in case I do not use the official Arch kernel?
 
|answer=Kernels prior to 2.6.39 are unsupported.
 
  
This is a partial list of required/recommended options, there might be more:
+
{{Expansion|How does it work with instantiated units?}}
  
{{bc|<nowiki>
+
Arch Linux ships with {{ic|/usr/lib/systemd/system-preset/99-default.preset}} containing {{ic|disable *}}. This causes ''systemctl preset'' to disable all units by default, such that when a new package is installed, the user must manually enable the unit.
CONFIG_AUDIT=y (recommended)
 
CONFIG_AUDIT_LOGINUID_IMMUTABLE=y (not required, may break sysvinit compat)
 
CONFIG_CGROUPS=y
 
CONFIG_IPV6=[y|m] (highly recommended)
 
CONFIG_UEVENT_HELPER_PATH="" (if you don't use an initramfs)
 
CONFIG_DEVTMPFS=y
 
CONFIG_DEVTMPFS_MOUNT=y (recommended, if you don't use an initramfs)
 
CONFIG_RTC_DRV_CMOS=y (highly recommended)
 
CONFIG_FANOTIFY=y (required for readahead)
 
CONFIG_AUTOFS4_FS=[y|m]
 
CONFIG_TMPFS_POSIX_ACL=y (recommended, if you want to use pam_systemd.so)
 
</nowiki>}}}}
 
  
{{FAQ
+
If this behavior is not desired, simply create a symlink from {{ic|/etc/systemd/system-preset/99-default.preset}} to {{ic|/dev/null}} in order to override the configuration file. This will cause ''systemctl preset'' to enable all units that get installed—regardless of unit type—unless specified in another file in one ''systemctl preset'''s configuration directories. User units are not affected. See {{man|5|systemd.preset}} for more information.
|question=What other units does a unit depend on?
 
|answer=For example, if you want to figure out which services a target like {{ic|multi-user.target}} pulls in, use something like this:
 
{{hc|$ systemctl show -p "Wants" multi-user.target|2=Wants=rc-local.service avahi-daemon.service rpcbind.service NetworkManager.service acpid.service dbus.service atd.service crond.service auditd.service ntpd.service udisks.service bluetooth.service cups.service wpa_supplicant.service getty.target modem-manager.service portreserve.service abrtd.service yum-updatesd.service upowerd.service test-first.service pcscd.service rsyslog.service haldaemon.service remote-fs.target plymouth-quit.service systemd-update-utmp-runlevel.service sendmail.service lvm2-monitor.service cpuspeed.service udev-post.service mdmonitor.service iscsid.service livesys.service livesys-late.service irqbalance.service iscsi.service}}
 
  
Instead of {{ic|Wants}} you might also try {{ic|WantedBy}}, {{ic|Requires}}, {{ic|RequiredBy}}, {{ic|Conflicts}}, {{ic|ConflictedBy}}, {{ic|Before}}, {{ic|After}} for the respective types of dependencies and their inverse.}}
+
{{Note|Enabling all units by default may cause problems with packages that contain two or more mutually exclusive units. ''systemctl preset'' is designed to be used by distributions and spins or system administrators. In the case where two conflicting units would be enabled, you should explicitly specify which one is to be disabled in a preset configuration file as specified in the manpage for {{ic|systemd.preset}}.}}
  
{{FAQ
+
=== Sandboxing application environments ===
|question=My computer shuts down, but the power stays on.
+
A unit file can be created as a sandbox to isolate applications and their processes within a hardened virtual environment. systemd leverages [[wikipedia:Linux_namespaces|namespaces]], white-/blacklisting of [[Capabilities]], and [[control groups]] to container processes through an extensive [https://www.freedesktop.org/software/systemd/man/systemd.exec.html execution environment configuration].
|answer=Use:
 
$ systemctl poweroff
 
Instead of {{ic|systemctl halt}}.}}
 
  
{{FAQ
+
The enhancement of an existing systemd unit file with application sandboxing typically requires trial-and-error tests accompanied by the generous use of {{Pkg|strace}}, [[wikipedia:Standard_streams#Standard_error_.28stderr.29|stderr]] and [https://www.freedesktop.org/software/systemd/man/journalctl.html journalctl] error logging and output facilities. You may want to first search upstream documentation for already done tests to base trials on.
|question=After migrating to systemd, why won't my fakeRAID mount?
 
|answer=Be sure you use {{bc|# systemctl enable dmraid.service}}
 
}}
 
  
{{FAQ
+
Some examples on how sandboxing with systemd can be deployed:
|question=How can I make a script start during the boot process?
+
* {{Ic|CapabilityBoundingSet}} defines a whitelisted set of allowed capabilities, but may also be used to blacklist a specific capability for a unit.
|answer=Create a new file in {{ic|/etc/systemd/system}} (e.g. ''myscript''.service) and add the following contents:
+
** The {{Ic|CAP_SYS_ADM}} capability, for example, which should be one of the [https://lwn.net/Articles/486306/ goals of a secure sandbox]: {{ic|1=CapabilityBoundingSet=~ CAP_SYS_ADM}}
{{bc|<nowiki>
 
[Unit]
 
Description=My script
 
  
[Service]
+
== Troubleshooting ==
ExecStart=/usr/bin/my-script
 
  
[Install]
+
=== Investigating systemd errors ===
WantedBy=multi-user.target
 
</nowiki>}}
 
Then
 
{{bc|# systemctl enable ''myscript''.service}}
 
This example assumes you want your script to start up when the target multi-user is launched.
 
}}
 
  
== Optimization ==
+
As an example, we will investigate an error with {{ic|systemd-modules-load}} service:
=== systemd-analyze ===
 
Systemd provides a tool called {{ic|systemd-analyze}} that allows you to analyze your boot process so you can see which unit files are causing your boot process to slow down. You can then optimize your system accordingly. You have to install {{Pkg|python2-dbus}} and {{Pkg|python2-cairo}} to use it.
 
  
To see how much time was spent in kernel-/userspace on boot, simply use:
+
'''1.''' Lets find the ''systemd'' services which fail to start at boot time:
{{bc|$ systemd-analyze}}
 
{{Tip|If you add the {{ic|timestamp}} hook to your {{ic|HOOKS}} array in {{ic|/etc/mkinitcpio.conf}} and rebuild your initramfs, {{ic|systemd-analyze}} will also be able to show you how much time was spent in the initramfs.}}
 
  
To list the started unit files, sorted by the time each of them took to start up:
+
{{hc|1=$ systemctl --state=failed|2=
{{bc|$ systemd-analyze blame}}
+
systemd-modules-load.service  loaded '''failed failed'''  Load Kernel Modules}}
  
You can also create a SVG file which describes your boot process grapically, similiar to [[Bootchart]]:
+
Another way is to live log ''systemd'' messages:
{{bc|$ systemd-analyze plot > plot.svg}}
 
  
====Enabling bootchart in conjunction with systemd====
+
$ journalctl -fp err
You can use a version of bootchart to visualize the boot sequence.
 
Since you are not able to put a second init into the kernel command line you won't be able to use any of the standard bootchart setups. However the {{AUR|bootchart2}} package from [[AUR]] comes with an undocumented systemd service. After you've installed bootchart2 do:
 
{{bc|# systemctl enable bootchart.service}}
 
Read the [https://github.com/mmeeks/bootchart bootchart documentation] for further details on using this version of bootchart.
 
  
=== Shell Shortcuts ===
+
'''2.''' Ok, we found a problem with {{ic|systemd-modules-load}} service. We want to know more:
systemd daemon management requires a bit more text entry to accomplish tasks such as start, stopped, enabling, checking status, etc. The following functions can be added to one's {{ic|~/.bashrc}} file to help streamline interactions with systemd and to improve the overall experience.
+
{{hc|$ systemctl status systemd-modules-load|2=
 +
systemd-modules-load.service - Load Kernel Modules
 +
  Loaded: loaded (/usr/lib/systemd/system/systemd-modules-load.service; static)
 +
  Active: '''failed''' (Result: exit-code) since So 2013-08-25 11:48:13 CEST; 32s ago
 +
    Docs: man:systemd-modules-load.service(8).
 +
          man:modules-load.d(5)
 +
  Process: '''15630''' ExecStart=/usr/lib/systemd/systemd-modules-load ('''code=exited, status=1/FAILURE''')
 +
}}
 +
If the {{ic|Process ID}} is not listed, just restart the failed service with {{ic|systemctl restart systemd-modules-load}}
  
{{bc|<nowiki>if ! systemd-notify --booted; then # not using systemd
+
'''3.''' Now we have the process id (PID) to investigate this error in depth. Enter the following command with the current {{ic|Process ID}} (here: 15630):
  start() {
+
{{hc|1=$ journalctl _PID=15630|2=
    sudo rc.d start $1
+
-- Logs begin at Sa 2013-05-25 10:31:12 CEST, end at So 2013-08-25 11:51:17 CEST. --
  }
+
Aug 25 11:48:13 mypc systemd-modules-load[15630]: '''Failed to find module 'blacklist usblp''''
 +
Aug 25 11:48:13 mypc systemd-modules-load[15630]: '''Failed to find module 'install usblp /bin/false''''
 +
}}
  
   restart() {
+
'''4.''' We see that some of the kernel module configs have wrong settings. Therefore we have a look at these settings in {{ic|/etc/modules-load.d/}}:
     sudo rc.d restart $1
+
{{hc|$ ls -Al /etc/modules-load.d/|
   }
+
...
 +
-rw-r--r--  1 root root    79  1. Dez 2012  blacklist.conf
 +
-rw-r--r--   1 root root    1  2. Mär 14:30 encrypt.conf
 +
-rw-r--r--  1 root root     3  5. Dez 2012  printing.conf
 +
-rw-r--r--  1 root root    6 14. Jul 11:01 realtek.conf
 +
-rw-r--r--   1 root root    65  2. Jun 23:01 virtualbox.conf
 +
...
 +
}}
  
  stop() {
+
'''5.''' The {{ic|Failed to find module 'blacklist usblp'}} error message might be related to a wrong setting inside of {{ic|blacklist.conf}}. Lets deactivate it with inserting a trailing '''#''' before each option we found via step 3:
    sudo rc.d stop $1
+
{{hc|/etc/modules-load.d/blacklist.conf|
  }
+
'''#''' blacklist usblp
else
+
'''#''' install usblp /bin/false
  start() {
+
}}
    sudo systemctl start $1
 
  }
 
  
  restart() {
+
'''6.''' Now, try to start {{ic|systemd-modules-load}}:
    sudo systemctl restart $1
+
# systemctl start systemd-modules-load
  }
+
If it was successful, this should not prompt anything. If you see any error, go back to step 3 and use the new PID for solving the errors left.
  
  stop() {
+
If everything is ok, you can verify that the service was started successfully with:
    sudo systemctl stop $1
+
{{hc|$ systemctl status systemd-modules-load|2=
  }
+
systemd-modules-load.service - Load Kernel Modules
 +
  Loaded: '''loaded''' (/usr/lib/systemd/system/systemd-modules-load.service; static)
 +
  Active: '''active (exited)''' since So 2013-08-25 12:22:31 CEST; 34s ago
 +
    Docs: man:systemd-modules-load.service(8)
 +
          man:modules-load.d(5)
 +
Process: 19005 ExecStart=/usr/lib/systemd/systemd-modules-load (code=exited, status=0/SUCCESS)
 +
Aug 25 12:22:31 mypc systemd[1]: '''Started Load Kernel Modules'''.
 +
}}
  
  enable() {
+
=== Diagnosing boot problems ===
    sudo systemctl enable $1
 
  }
 
  
  status() {
+
''systemd'' has several options for diagnosing problems with the boot process. See [[boot debugging]] for more general instructions and options to capture boot messages before ''systemd'' takes over the [[boot process]]. Also see the [https://freedesktop.org/wiki/Software/systemd/Debugging/ systemd debugging documentation].
    sudo systemctl status $1
 
  }
 
  
  disable() {
+
=== Diagnosing a service ===
    sudo systemctl disable $1
 
  }
 
fi
 
</nowiki>}}
 
  
=== Less output ===
+
If some ''systemd'' service misbehaves or you want to get more information about what is happening, set the {{ic|SYSTEMD_LOG_LEVEL}} [[environment variable]] to {{ic|debug}}. For example, to run the ''systemd-networkd'' daemon in debug mode:
Change {{ic|verbose}} to {{ic|quiet}} on the bootloader's kernel line. For some systems, particularly those with an SSD, the slow performance of the TTY is actually a bottleneck, and so less output means faster booting.
 
  
=== Early start ===
+
Add a [[#Drop-in files|drop-in file]] for the service adding the two lines:
One central feature of systemd is [[D-Bus]] and socket activation, this causes services to be started when they are first accessed, and is generally a good thing. However, if you know that a service (like [[ConsoleKit]]) will always be started during boot, then the overall boot time might be reduced by starting it as early as possible. This can be achieved (if the service file is set up for it, which in most cases it is) by issuing:
 
  
{{bc|# systemctl enable console-kit-daemon.service}}
+
[Service]
 +
Environment=SYSTEMD_LOG_LEVEL=debug
  
This will cause systemd to start ConsoleKit as soon as possible, without causing races with the socket or D-Bus activation.
+
Or equivalently, set the environment variable manually:
  
=== Automount ===
+
# SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd
The default setup will fsck and mount all filesystems before starting most daemons and services. If you have a large {{ic|/home}} partition, it might be better to allow services that do not depend on {{ic|/home}} to start while {{ic|/home}} is being fsck'ed. This can be achieved by adding the following options to the fstab entry of your {{ic|/home}} partition:
 
  
noauto,x-systemd.automount
+
then [[restart]] ''systemd-networkd'' and watch the journal for the service with the {{ic|-f}}/{{ic|--follow}} option.
  
This will fsck and mount {{ic|/home}} when it is first accessed, and the kernel will buffer all file access to {{ic|/home}} until it is ready.
+
=== Shutdown/reboot takes terribly long ===
  
If you have encrypted filesystems with keyfiles, you can also add the {{ic|noauto}} parameter to the corresponding entries in {{ic|/etc/crypttab}}. systemd will then not open the encrypted device on boot, but instead wait until it is actually accessed and then automatically open it with the specified keyfile before mounting it. This might save a few seconds on boot if you are using an encrypted RAID device for example, because systemd doesn't have to wait for the device to become available. For example:
+
If the shutdown process takes a very long time (or seems to freeze) most likely a service not exiting is to blame. ''systemd'' waits some time for each service to exit before trying to kill it. To find out if you are affected, see [https://freedesktop.org/wiki/Software/systemd/Debugging/#shutdowncompleteseventually this article].
{{hc|/etc/crypttab|data /dev/md0 /root/key noauto}}
 
  
=== Readahead ===
+
=== Short lived processes do not seem to log any output ===
systemd comes with its own readahead implementation, this should in principle improve boot time. However, depending on your kernel version and the type of your hard drive, your mileage may vary (i.e. it might be slower). To enable, do:
 
  
{{bc|<nowiki># systemctl enable systemd-readahead-collect.service systemd-readahead-replay.service</nowiki>}}
+
If {{ic|journalctl -u foounit}} does not show any output for a short lived service, look at the PID instead. For example, if {{ic|systemd-modules-load.service}} fails, and {{ic|systemctl status systemd-modules-load}} shows that it ran as PID 123, then you might be able to see output in the journal for that PID, i.e. {{ic|journalctl -b _PID&#61;123}}. Metadata fields for the journal such as {{ic|_SYSTEMD_UNIT}} and {{ic|_COMM}} are collected asynchronously and rely on the {{ic|/proc}} directory for the process existing. Fixing this requires fixing the kernel to provide this data via a socket connection, similar to {{ic|SCM_CREDENTIALS}}. In short, it is a [https://github.com/systemd/systemd/issues/2913 bug]. Keep in mind that immediately failed services might not print anything to the journal as per design of systemd.
  
Remember that in order for the readahead to work its magic, you should reboot a couple of times.
+
=== Boot time increasing over time ===
  
=== User sessions ===
+
After using {{ic|systemd-analyze}} a number of users have noticed that their boot time has increased significantly in comparison with what it used to be. After using {{ic|systemd-analyze blame}} [[NetworkManager]] is being reported as taking an unusually large amount of time to start.  
systemd can divide user sessions into cgroups. Add {{ic|session optional pam_systemd.so}} to your relevant {{ic|/etc/pam.d/}} files (e.g., {{ic|login}} for tty logins, {{ic|sshd}} for remote access, {{ic|kde}} for password kdm logins, {{ic|kde-np}} for automatic kdm logins).
 
  
Before:
+
The problem for some users has been due to {{ic|/var/log/journal}} becoming too large. This may have other impacts on performance, such as for {{ic|systemctl status}} or {{ic|journalctl}}. As such the solution is to remove every file within the folder (ideally making a backup of it somewhere, at least temporarily) and then setting a journal file size limit as described in [[Systemd/Journal#Journal size limit]].
{{hc|$ systemd-cgls systemd:/system/getty@.service|
 
systemd:/system/getty@.service:
 
├ tty5
 
│ └ 904 /sbin/agetty tty5 38400
 
├ tty2
 
│ ├ 13312 /bin/login --
 
│ └ 15765 -zsh
 
[…]}}
 
After:
 
{{hc|$ systemd-cgls systemd:/user/example/|
 
systemd:/user/example/:
 
├ 4
 
│ ├  902 /bin/login --
 
│ └ 16016 -zsh
 
[…]}}
 
  
Further, you can replace [[ConsoleKit]]'s functionality with systemd. To do this, {{Pkg|polkit}} needs to be rebuilt from [[ABS]] with systemd enabled ({{ic|--enable-systemd}}), and stuff like USB automounting will work without consolekit. DBus supports systemd since version 1.6.0, so there's no longer need to build it from Git.
+
=== systemd-tmpfiles-setup.service fails to start at boot ===
  
== Troubleshooting ==
+
Starting with systemd 219, {{ic|/usr/lib/tmpfiles.d/systemd.conf}} specifies ACL attributes for directories under {{ic|/var/log/journal}} and, therefore, requires ACL support to be enabled for the filesystem the journal resides on.
=== Shutdown/Reboot takes terribly long ===
 
If the shutdown process takes a very long time (or seems to freeze) most likely a service not exiting is to blame. systemd waits some time for each service to exit before trying to kill it.
 
To find out if you are affected see [http://freedesktop.org/wiki/Software/systemd/Debugging#Shutdown_Completes_Eventually this article].
 
==== SLiM and xfce-session ====
 
One setup that can produce a shutdown freeze is Xfce in conjunction with SLiM: Shutting down/rebooting using xfce-session will cause slim.service to hang for half a minute until systemd kills it the hard way.
 
One workaround is to create a modified {{ic|slim.service}}:
 
{{hc|/etc/systemd/system/slim.service|<nowiki>
 
[Unit]
 
Description=SLiM Simple Login Manager
 
After=systemd-user-sessions.service
 
  
[Service]
+
See [[Access Control Lists#Enabling ACL]] for instructions on how to enable ACL on the filesystem that houses {{ic|/var/log/journal}}.
Type=forking
 
PIDFile=/var/lock/slim.lock
 
ExecStart=/usr/bin/slim -d
 
ExecStop=/bin/kill -9 $MAINPID
 
ExecStopPost=/bin/rm /var/lock/slim.lock
 
  
[Install]
+
=== systemd version printed on boot is not the same as installed package version ===
WantedBy=graphical.target</nowiki>}}
 
This causes SLiM to be terminated using SIGKILL. Since the lock file is also removed this does not cause a problem.
 
  
=== If the CUPS service isn't starting on demand ===
+
You need to [[Mkinitcpio#Image_creation_and_activation|regenerate your initramfs]] and the versions should match.
  
{{Poor writing|Written in first person.}}
+
{{Tip|1=A pacman hook can be used to automatically regenerate the initramfs every time {{pkg|systemd}} is upgraded. See [https://bbs.archlinux.org/viewtopic.php?id=215411 this forum thread] and [[Pacman#Hooks]].}}
  
I found on my machine, even after running "systemctl enable cups.service", cups would never work until I manually issued "systemctl start cups.service". To remedy this you can manually symlink the cups service so it is automatically started at boot:
+
=== Disable emergency mode on remote machine ===
  
{{bc|<nowiki># ln -s '/usr/lib/systemd/system/cups.service' '/etc/systemd/system/multi-user.target.wants/cups.service'</nowiki>}}
+
You may want to disable emergency mode on a remote machine, for example, a virtual machine hosted at Azure or Google Cloud. It is because if emergency mode is triggered, the machine will be blocked from connecting to network.
  
I found that "systemctl enable cupsd.service" fails with a complaint about not finding the file. I'm guessing this is because it is a symlink to cups.service. Apparently systemctl doesn't like symlinks. I'm not sure if this is user error (I wasn't meant to use the symlink for this purpose) or a bug but either way, specifying cups.service seemed to work although I haven't tested it yet.
+
# systemctl mask emergency.service
 +
# systemctl mask emergency.target
  
=== Disable warning bell ===
+
== See also ==
Add command {{ic|xset -b}} to the {{ic|.xinitrc}} file.
 
Discussion on [https://bbs.archlinux.org/viewtopic.php?pid=1148781 this] forum topic.
 
  
== See also==
+
*[[Wikipedia:systemd|Wikipedia article]]
*[http://www.freedesktop.org/wiki/Software/systemd Official Web Site]
+
*[https://www.freedesktop.org/wiki/Software/systemd systemd Official web site]
*[http://0pointer.de/public/systemd-man/ Manual Pages]
+
**[https://www.freedesktop.org/wiki/Software/systemd/Optimizations systemd optimizations]
*[http://freedesktop.org/wiki/Software/systemd/Optimizations systemd Optimizations]
+
**[https://www.freedesktop.org/wiki/Software/systemd/FrequentlyAskedQuestions systemd FAQ]
*[http://www.freedesktop.org/wiki/Software/systemd/FrequentlyAskedQuestions FAQ]
+
**[https://www.freedesktop.org/wiki/Software/systemd/TipsAndTricks systemd Tips and tricks]
*[http://www.freedesktop.org/wiki/Software/systemd/TipsAndTricks Tips And Tricks]
+
*[https://www.freedesktop.org/software/systemd/man/ Manual pages]
 +
*Other distributions
 +
**[https://wiki.gentoo.org/wiki/Systemd Gentoo Wiki systemd page]
 +
**[https://fedoraproject.org/wiki/Systemd Fedora Project - About systemd]
 +
**[https://fedoraproject.org/wiki/How_to_debug_Systemd_problems Fedora Project - How to debug systemd problems]
 +
**[https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet Fedora Project - SysVinit to systemd cheatsheet]
 +
**[[debian:systemd|Debian Wiki systemd page]]
 +
*[http://0pointer.de/blog/projects/systemd.html Lennart's blog story], [http://0pointer.de/blog/projects/systemd-update.html update 1], [http://0pointer.de/blog/projects/systemd-update-2.html update 2], [http://0pointer.de/blog/projects/systemd-update-3.html update 3], [http://0pointer.de/blog/projects/why.html summary]
 
*[http://0pointer.de/public/systemd-ebook-psankar.pdf systemd for Administrators (PDF)]
 
*[http://0pointer.de/public/systemd-ebook-psankar.pdf systemd for Administrators (PDF)]
*[http://fedoraproject.org/wiki/Systemd About systemd on Fedora Project]
+
*[https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units How To Use Systemctl to Manage Systemd Services and Units ]
*[http://fedoraproject.org/wiki/How_to_debug_Systemd_problems How to debug Systemd problems]
+
*[https://dvdhrm.wordpress.com/2013/08/24/session-management-on-linux/ Session management with systemd-logind]
*[http://www.h-online.com/open/features/Booting-up-Tools-and-tips-for-systemd-1570630.html Booting up: Tools and tips for systemd, a Linux init tool. In The H]
+
*[[Emacs#Syntax highlighting for systemd Files|Emacs Syntax highlighting for Systemd files]]
*[http://0pointer.de/blog/projects/systemd.html Lennart's blog story]
+
*[http://www.h-online.com/open/features/Control-Centre-The-systemd-Linux-init-system-1565543.html Two] [http://www.h-online.com/open/features/Booting-up-Tools-and-tips-for-systemd-1570630.html part] introductory article in ''The H Open'' magazine.
*[http://0pointer.de/blog/projects/systemd-update.html status update]
 
*[http://0pointer.de/blog/projects/systemd-update-2.html status update2]
 
*[http://0pointer.de/blog/projects/systemd-update-3.html status update3]
 
*[http://0pointer.de/blog/projects/why.html most recent summary]
 

Latest revision as of 09:02, 6 September 2019

From the project web page:

systemd is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system. systemd provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux control groups, maintains mount and automount points, and implements an elaborate transactional dependency-based service control logic. systemd supports SysV and LSB init scripts and works as a replacement for sysvinit. Other parts include a logging daemon, utilities to control basic system configuration like the hostname, date, locale, maintain a list of logged-in users and running containers and virtual machines, system accounts, runtime directories and settings, and daemons to manage simple network configuration, network time synchronization, log forwarding, and name resolution.
Note: For a detailed explanation of why Arch moved to systemd, see this forum post.

Basic systemctl usage

The main command used to introspect and control systemd is systemctl. Some of its uses are examining the system state and managing the system and services. See systemctl(1) for more details.

Tip:
  • You can use all of the following systemctl commands with the -H user@host switch to control a systemd instance on a remote machine. This will use SSH to connect to the remote systemd instance.
  • Plasma users can install systemd-kcmAUR as a graphical frontend for systemctl. After installing the module will be added under System administration.

Analyzing the system state

Show system status using:

$ systemctl status

List running units:

$ systemctl

or:

$ systemctl list-units

List failed units:

$ systemctl --failed

The available unit files can be seen in /usr/lib/systemd/system/ and /etc/systemd/system/ (the latter takes precedence). List installed unit files with:

$ systemctl list-unit-files

Show the cgroup slice, memory and parent for a PID:

$ systemctl status pid

Using units

Units can be, for example, services (.service), mount points (.mount), devices (.device) or sockets (.socket).

When using systemctl, you generally have to specify the complete name of the unit file, including its suffix, for example sshd.socket. There are however a few short forms when specifying the unit in the following systemctl commands:

  • If you do not specify the suffix, systemctl will assume .service. For example, netctl and netctl.service are equivalent.
  • Mount points will automatically be translated into the appropriate .mount unit. For example, specifying /home is equivalent to home.mount.
  • Similar to mount points, devices are automatically translated into the appropriate .device unit, therefore specifying /dev/sda2 is equivalent to dev-sda2.device.

See systemd.unit(5) for details.

Note: Some unit names contain an @ sign (e.g. name@string.service): this means that they are instances of a template unit, whose actual file name does not contain the string part (e.g. name@.service). string is called the instance identifier, and is similar to an argument that is passed to the template unit when called with the systemctl command: in the unit file it will substitute the %i specifier.

To be more accurate, before trying to instantiate the name@.suffix template unit, systemd will actually look for a unit with the exact name@string.suffix file name, although by convention such a "clash" happens rarely, i.e. most unit files containing an @ sign are meant to be templates. Also, if a template unit is called without an instance identifier, it will just fail, since the %i specifier cannot be substituted.

Tip:
  • Most of the following commands also work if multiple units are specified, see systemctl(1) for more information.
  • The --now switch can be used in conjunction with enable, disable, and mask to respectively start, stop, or mask the unit immediately rather than after rebooting.
  • A package may offer units for different purposes. If you just installed a package, pacman -Qql package | grep -Fe .service -e .socket can be used to check and find them.

Start a unit immediately:

# systemctl start unit

Stop a unit immediately:

# systemctl stop unit

Restart a unit:

# systemctl restart unit

Ask a unit to reload its configuration:

# systemctl reload unit

Show the status of a unit, including whether it is running or not:

$ systemctl status unit

Check whether a unit is already enabled or not:

$ systemctl is-enabled unit

Enable a unit to be started on bootup:

# systemctl enable unit

Enable a unit to be started on bootup and Start immediately:

# systemctl enable --now unit

Disable a unit to not start during bootup:

# systemctl disable unit

Mask a unit to make it impossible to start it (both manually and as a dependency, which makes masking dangerous):

# systemctl mask unit

Unmask a unit:

# systemctl unmask unit

Show the manual page associated with a unit (this has to be supported by the unit file):

$ systemctl help unit

Reload systemd manager configuration, scanning for new or changed units:

Note: This does not ask the changed units to reload their own configurations. See reload example above.
# systemctl daemon-reload

Power management

polkit is necessary for power management as an unprivileged user. If you are in a local systemd-logind user session and no other session is active, the following commands will work without root privileges. If not (for example, because another user is logged into a tty), systemd will automatically ask you for the root password.

Shut down and reboot the system:

$ systemctl reboot

Shut down and power-off the system:

$ systemctl poweroff

Suspend the system:

$ systemctl suspend

Put the system into hibernation:

$ systemctl hibernate

Put the system into hybrid-sleep state (or suspend-to-both):

$ systemctl hybrid-sleep

Writing unit files

The syntax of systemd's unit files is inspired by XDG Desktop Entry Specification .desktop files, which are in turn inspired by Microsoft Windows .ini files. Unit files are loaded from multiple locations (to see the full list, run systemctl show --property=UnitPath), but the main ones are (listed from lowest to highest precedence):

  • /usr/lib/systemd/system/: units provided by installed packages
  • /etc/systemd/system/: units installed by the system administrator
Note:
  • The load paths are completely different when running systemd in user mode.
  • systemd unit names may only contain ASCII alphanumeric characters, underscores and periods. All other characters must be replaced by C-style "\x2d" escapes, or employ their predefined semantics ('@', '-'). See systemd.unit(5) and systemd-escape(1) for more information.

Look at the units installed by your packages for examples, as well as the annotated example section of systemd.service(5).

Tip: Comments prepended with # may be used in unit-files as well, but only in new lines. Do not use end-line comments after systemd parameters or the unit will fail to activate.

Handling dependencies

With systemd, dependencies can be resolved by designing the unit files correctly. The most typical case is that the unit A requires the unit B to be running before A is started. In that case add Requires=B and After=B to the [Unit] section of A. If the dependency is optional, add Wants=B and After=B instead. Note that Wants= and Requires= do not imply After=, meaning that if After= is not specified, the two units will be started in parallel.

Dependencies are typically placed on services and not on #Targets. For example, network.target is pulled in by whatever service configures your network interfaces, therefore ordering your custom unit after it is sufficient since network.target is started anyway.

Service types

There are several different start-up types to consider when writing a custom service file. This is set with the Type= parameter in the [Service] section:

  • Type=simple (default): systemd considers the service to be started up immediately. The process must not fork. Do not use this type if other services need to be ordered on this service, unless it is socket activated.
  • Type=forking: systemd considers the service started up once the process forks and the parent has exited. For classic daemons use this type unless you know that it is not necessary. You should specify PIDFile= as well so systemd can keep track of the main process.
  • Type=oneshot: this is useful for scripts that do a single job and then exit. You may want to set RemainAfterExit=yes as well so that systemd still considers the service as active after the process has exited.
  • Type=notify: identical to Type=simple, but with the stipulation that the daemon will send a signal to systemd when it is ready. The reference implementation for this notification is provided by libsystemd-daemon.so.
  • Type=dbus: the service is considered ready when the specified BusName appears on DBus's system bus.
  • Type=idle: systemd will delay execution of the service binary until all jobs are dispatched. Other than that behavior is very similar to Type=simple.

See the systemd.service(5) man page for a more detailed explanation of the Type values.

Editing provided units

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements. See Help:Style for reference.Tango-edit-clear.png

Reason: Should be renamed to more descriptive Modifying provided units. (Discuss in Talk:Edit#Deprecation)

To avoid conflicts with pacman, unit files provided by packages should not be directly edited. There are two safe ways to modify a unit without touching the original file: create a new unit file which overrides the original unit or create drop-in snippets which are applied on top of the original unit. For both methods, you must reload the unit afterwards to apply your changes. This can be done either by editing the unit with systemctl edit (which reloads the unit automatically) or by reloading all units with:

# systemctl daemon-reload
Tip:
  • You can use systemd-delta to see which unit files have been overridden or extended and what exactly has been changed.
  • Use systemctl cat unit to view the content of a unit file and all associated drop-in snippets.

Replacement unit files

To replace the unit file /usr/lib/systemd/system/unit, create the file /etc/systemd/system/unit and reenable the unit to update the symlinks:

# systemctl reenable unit

Alternatively, run:

# systemctl edit --full unit

This opens /etc/systemd/system/unit in your editor (copying the installed version if it does not exist yet) and automatically reloads it when you finish editing.

Note: The replacement units will keep on being used even if Pacman updates the original units in the future. This method makes system maintenance more difficult and therefore the next approach is preferred.

Drop-in files

To create drop-in files for the unit file /usr/lib/systemd/system/unit, create the directory /etc/systemd/system/unit.d/ and place .conf files there to override or add new options. systemd will parse and apply these files on top of the original unit.

The easiest way to do this is to run:

# systemctl edit unit

This opens the file /etc/systemd/system/unit.d/override.conf in your text editor (creating it if necessary) and automatically reloads the unit when you are done editing.

Note: Not all keys can be overridden with drop-in files. For example, for changing Conflicts= a replacement file is necessary.

Revert to vendor version

To revert any changes to a unit made using systemctl edit do:

# systemctl revert unit

Examples

For example, if you simply want to add an additional dependency to a unit, you may create the following file:

/etc/systemd/system/unit.d/customdependency.conf
[Unit]
Requires=new dependency
After=new dependency

As another example, in order to replace the ExecStart directive for a unit that is not of type oneshot, create the following file:

/etc/systemd/system/unit.d/customexec.conf
[Service]
ExecStart=
ExecStart=new command

Note how ExecStart must be cleared before being re-assigned [1]. The same holds for every item that can be specified multiple times, e.g. OnCalendar for timers.

One more example to automatically restart a service:

/etc/systemd/system/unit.d/restart.conf
[Service]
Restart=always
RestartSec=30

Targets

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements. See Help:Style for reference.Tango-edit-clear.png

Reason: Unclear description, copy-pasted content (explicitly mentions "Fedora"). (Discuss in "Targets"_more_clearly Talk:Systemd#Make section "Targets" more clearly)

systemd uses targets to group units together via dependencies and as standardized synchronization points. They serve a similar purpose as runlevels but act a little different. Each target is named instead of numbered and is intended to serve a specific purpose with the possibility of having multiple ones active at the same time. Some targets are implemented by inheriting all of the services of another target and adding additional services to it. There are systemd targets that mimic the common SystemVinit runlevels so you can still switch targets using the familiar telinit RUNLEVEL command.

Get current targets

The following should be used under systemd instead of running runlevel:

$ systemctl list-units --type=target

Create custom target

The runlevels that held a defined meaning under sysvinit (i.e., 0, 1, 3, 5, and 6); have a 1:1 mapping with a specific systemd target. Unfortunately, there is no good way to do the same for the user-defined runlevels like 2 and 4. If you make use of those it is suggested that you make a new named systemd target as /etc/systemd/system/your target that takes one of the existing runlevels as a base (you can look at /usr/lib/systemd/system/graphical.target as an example), make a directory /etc/systemd/system/your target.wants, and then symlink the additional services from /usr/lib/systemd/system/ that you wish to enable.

Mapping between SysV runlevels and systemd targets

SysV Runlevel systemd Target Notes
0 runlevel0.target, poweroff.target Halt the system.
1, s, single runlevel1.target, rescue.target Single user mode.
2, 4 runlevel2.target, runlevel4.target, multi-user.target User-defined/Site-specific runlevels. By default, identical to 3.
3 runlevel3.target, multi-user.target Multi-user, non-graphical. Users can usually login via multiple consoles or via the network.
5 runlevel5.target, graphical.target Multi-user, graphical. Usually has all the services of runlevel 3 plus a graphical login.
6 runlevel6.target, reboot.target Reboot
emergency emergency.target Emergency shell

Change current target

In systemd targets are exposed via target units. You can change them like this:

# systemctl isolate graphical.target

This will only change the current target, and has no effect on the next boot. This is equivalent to commands such as telinit 3 or telinit 5 in Sysvinit.

Change default target to boot into

The standard target is default.target, which is a symlink to graphical.target. This roughly corresponds to the old runlevel 5.

To verify the current target with systemctl:

$ systemctl get-default

To change the default target to boot into, change the default.target symlink. With systemctl:

# systemctl set-default multi-user.target
Removed /etc/systemd/system/default.target.
Created symlink /etc/systemd/system/default.target -> /usr/lib/systemd/system/multi-user.target.

Alternatively, append one of the following kernel parameters to your bootloader:

  • systemd.unit=multi-user.target (which roughly corresponds to the old runlevel 3),
  • systemd.unit=rescue.target (which roughly corresponds to the old runlevel 1).

Default target order

Systemd chooses the default.target according to the following order:

  1. Kernel parameter shown above
  2. Symlink of /etc/systemd/system/default.target
  3. Symlink of /usr/lib/systemd/system/default.target

Temporary files

"systemd-tmpfiles creates, deletes and cleans up volatile and temporary files and directories." It reads configuration files in /etc/tmpfiles.d/ and /usr/lib/tmpfiles.d/ to discover which actions to perform. Configuration files in the former directory take precedence over those in the latter directory.

Configuration files are usually provided together with service files, and they are named in the style of /usr/lib/tmpfiles.d/program.conf. For example, the Samba daemon expects the directory /run/samba to exist and to have the correct permissions. Therefore, the samba package ships with this configuration:

/usr/lib/tmpfiles.d/samba.conf
D /run/samba 0755 root root

Configuration files may also be used to write values into certain files on boot. For example, if you used /etc/rc.local to disable wakeup from USB devices with echo USBE > /proc/acpi/wakeup, you may use the following tmpfile instead:

/etc/tmpfiles.d/disable-usb-wake.conf
#    Path                  Mode UID  GID  Age Argument
w    /proc/acpi/wakeup     -    -    -    -   USBE

See the systemd-tmpfiles(8) and tmpfiles.d(5) man pages for details.

Note: This method may not work to set options in /sys since the systemd-tmpfiles-setup service may run before the appropriate device modules is loaded. In this case you could check whether the module has a parameter for the option you want to set with modinfo module and set this option with a config file in /etc/modprobe.d. Otherwise you will have to write a udev rule to set the appropriate attribute as soon as the device appears.

Timers

A timer is a unit configuration file whose name ends with .timer and encodes information about a timer controlled and supervised by systemd, for timer-based activation. See systemd/Timers.

Note: Timers can replace cron functionality to a great extent. See systemd/Timers#As a cron replacement.

Mounting

systemd is in charge of mounting the partitions and filesystems specified in /etc/fstab. The systemd-fstab-generator(8) translates all the entries in /etc/fstab into systemd units, this is performed at boot time and whenever the configuration of the system manager is reloaded.

systemd extends the usual fstab capabilities and offers additional mount options. These affect the dependencies of the mount unit, they can for example ensure that a mount is performed only once the network is up or only once another partition is mounted. The full list of specific systemd mount options, typically prefixed with x-systemd., is detailed in systemd.mount(5).

An example of these mount options in the context of automounting, which means mounting only when the resource is required rather than automatically at boot time, is provided in fstab#Automount with systemd.

GPT partition automounting

On a GPT partitioned disk systemd-gpt-auto-generator(8) will mount partitions following the Discoverable Partitions Specification, thus they can be omitted from fstab.

The automounting for a partition can be disabled by changing the partition's type GUID or setting the partition attribute bit 63 "do not automount", see gdisk#Prevent GPT partition automounting.

Tips and tricks

Running services after the network is up

To delay a service after the network is up, include the following dependencies in the .service file:

/etc/systemd/system/foo.service
[Unit]
...
Wants=network-online.target
After=network-online.target
...

The network wait service of the particular application that manages the network, must also be enabled so that network-online.target properly reflects the network status.

  • For the ones using NetworkManager, enable NetworkManager-wait-online.service.
  • In the case of netctl, enable the netctl-wait-online.service.
  • If using systemd-networkd, systemd-networkd-wait-online.service is by default enabled automatically whenever systemd-networkd.service has been enabled; check this is the case with systemctl is-enabled systemd-networkd-wait-online.service, there is no other action needed.

For more detailed explanations see Running services after the network is up in the systemd wiki.

Enable installed units by default

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: How does it work with instantiated units? (Discuss in Talk:Systemd#)

Arch Linux ships with /usr/lib/systemd/system-preset/99-default.preset containing disable *. This causes systemctl preset to disable all units by default, such that when a new package is installed, the user must manually enable the unit.

If this behavior is not desired, simply create a symlink from /etc/systemd/system-preset/99-default.preset to /dev/null in order to override the configuration file. This will cause systemctl preset to enable all units that get installed—regardless of unit type—unless specified in another file in one systemctl preset's configuration directories. User units are not affected. See systemd.preset(5) for more information.

Note: Enabling all units by default may cause problems with packages that contain two or more mutually exclusive units. systemctl preset is designed to be used by distributions and spins or system administrators. In the case where two conflicting units would be enabled, you should explicitly specify which one is to be disabled in a preset configuration file as specified in the manpage for systemd.preset.

Sandboxing application environments

A unit file can be created as a sandbox to isolate applications and their processes within a hardened virtual environment. systemd leverages namespaces, white-/blacklisting of Capabilities, and control groups to container processes through an extensive execution environment configuration.

The enhancement of an existing systemd unit file with application sandboxing typically requires trial-and-error tests accompanied by the generous use of strace, stderr and journalctl error logging and output facilities. You may want to first search upstream documentation for already done tests to base trials on.

Some examples on how sandboxing with systemd can be deployed:

  • CapabilityBoundingSet defines a whitelisted set of allowed capabilities, but may also be used to blacklist a specific capability for a unit.
    • The CAP_SYS_ADM capability, for example, which should be one of the goals of a secure sandbox: CapabilityBoundingSet=~ CAP_SYS_ADM

Troubleshooting

Investigating systemd errors

As an example, we will investigate an error with systemd-modules-load service:

1. Lets find the systemd services which fail to start at boot time:

$ systemctl --state=failed
systemd-modules-load.service   loaded failed failed  Load Kernel Modules

Another way is to live log systemd messages:

$ journalctl -fp err

2. Ok, we found a problem with systemd-modules-load service. We want to know more:

$ systemctl status systemd-modules-load
systemd-modules-load.service - Load Kernel Modules
   Loaded: loaded (/usr/lib/systemd/system/systemd-modules-load.service; static)
   Active: failed (Result: exit-code) since So 2013-08-25 11:48:13 CEST; 32s ago
     Docs: man:systemd-modules-load.service(8).
           man:modules-load.d(5)
  Process: 15630 ExecStart=/usr/lib/systemd/systemd-modules-load (code=exited, status=1/FAILURE)

If the Process ID is not listed, just restart the failed service with systemctl restart systemd-modules-load

3. Now we have the process id (PID) to investigate this error in depth. Enter the following command with the current Process ID (here: 15630):

$ journalctl _PID=15630
-- Logs begin at Sa 2013-05-25 10:31:12 CEST, end at So 2013-08-25 11:51:17 CEST. --
Aug 25 11:48:13 mypc systemd-modules-load[15630]: Failed to find module 'blacklist usblp'
Aug 25 11:48:13 mypc systemd-modules-load[15630]: Failed to find module 'install usblp /bin/false'

4. We see that some of the kernel module configs have wrong settings. Therefore we have a look at these settings in /etc/modules-load.d/:

$ ls -Al /etc/modules-load.d/
...
-rw-r--r--   1 root root    79  1. Dez 2012  blacklist.conf
-rw-r--r--   1 root root     1  2. Mär 14:30 encrypt.conf
-rw-r--r--   1 root root     3  5. Dez 2012  printing.conf
-rw-r--r--   1 root root     6 14. Jul 11:01 realtek.conf
-rw-r--r--   1 root root    65  2. Jun 23:01 virtualbox.conf
...

5. The Failed to find module 'blacklist usblp' error message might be related to a wrong setting inside of blacklist.conf. Lets deactivate it with inserting a trailing # before each option we found via step 3:

/etc/modules-load.d/blacklist.conf
# blacklist usblp
# install usblp /bin/false

6. Now, try to start systemd-modules-load:

# systemctl start systemd-modules-load

If it was successful, this should not prompt anything. If you see any error, go back to step 3 and use the new PID for solving the errors left.

If everything is ok, you can verify that the service was started successfully with:

$ systemctl status systemd-modules-load
systemd-modules-load.service - Load Kernel Modules
   Loaded: loaded (/usr/lib/systemd/system/systemd-modules-load.service; static)
   Active: active (exited) since So 2013-08-25 12:22:31 CEST; 34s ago
     Docs: man:systemd-modules-load.service(8)
           man:modules-load.d(5)
 Process: 19005 ExecStart=/usr/lib/systemd/systemd-modules-load (code=exited, status=0/SUCCESS)
Aug 25 12:22:31 mypc systemd[1]: Started Load Kernel Modules.

Diagnosing boot problems

systemd has several options for diagnosing problems with the boot process. See boot debugging for more general instructions and options to capture boot messages before systemd takes over the boot process. Also see the systemd debugging documentation.

Diagnosing a service

If some systemd service misbehaves or you want to get more information about what is happening, set the SYSTEMD_LOG_LEVEL environment variable to debug. For example, to run the systemd-networkd daemon in debug mode:

Add a drop-in file for the service adding the two lines:

[Service]
Environment=SYSTEMD_LOG_LEVEL=debug

Or equivalently, set the environment variable manually:

# SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd

then restart systemd-networkd and watch the journal for the service with the -f/--follow option.

Shutdown/reboot takes terribly long

If the shutdown process takes a very long time (or seems to freeze) most likely a service not exiting is to blame. systemd waits some time for each service to exit before trying to kill it. To find out if you are affected, see this article.

Short lived processes do not seem to log any output

If journalctl -u foounit does not show any output for a short lived service, look at the PID instead. For example, if systemd-modules-load.service fails, and systemctl status systemd-modules-load shows that it ran as PID 123, then you might be able to see output in the journal for that PID, i.e. journalctl -b _PID=123. Metadata fields for the journal such as _SYSTEMD_UNIT and _COMM are collected asynchronously and rely on the /proc directory for the process existing. Fixing this requires fixing the kernel to provide this data via a socket connection, similar to SCM_CREDENTIALS. In short, it is a bug. Keep in mind that immediately failed services might not print anything to the journal as per design of systemd.

Boot time increasing over time

After using systemd-analyze a number of users have noticed that their boot time has increased significantly in comparison with what it used to be. After using systemd-analyze blame NetworkManager is being reported as taking an unusually large amount of time to start.

The problem for some users has been due to /var/log/journal becoming too large. This may have other impacts on performance, such as for systemctl status or journalctl. As such the solution is to remove every file within the folder (ideally making a backup of it somewhere, at least temporarily) and then setting a journal file size limit as described in Systemd/Journal#Journal size limit.

systemd-tmpfiles-setup.service fails to start at boot

Starting with systemd 219, /usr/lib/tmpfiles.d/systemd.conf specifies ACL attributes for directories under /var/log/journal and, therefore, requires ACL support to be enabled for the filesystem the journal resides on.

See Access Control Lists#Enabling ACL for instructions on how to enable ACL on the filesystem that houses /var/log/journal.

systemd version printed on boot is not the same as installed package version

You need to regenerate your initramfs and the versions should match.

Tip: A pacman hook can be used to automatically regenerate the initramfs every time systemd is upgraded. See this forum thread and Pacman#Hooks.

Disable emergency mode on remote machine

You may want to disable emergency mode on a remote machine, for example, a virtual machine hosted at Azure or Google Cloud. It is because if emergency mode is triggered, the machine will be blocked from connecting to network.

# systemctl mask emergency.service
# systemctl mask emergency.target

See also