Difference between revisions of "Systemd"

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[[Category:Boot process]]
 
[[Category:Boot process]]
 
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[[zh-CN:Systemd]]
 
[[zh-CN:Systemd]]
 
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[[zh-TW:Systemd]]
{{Article summary start}}
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{{Related articles start}}
{{Article summary text|Covers how to install and configure systemd.}}
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{{Related|systemd/User}}
{{Article summary heading|Related}}
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{{Related|systemd/Timers}}
{{Article summary wiki|systemd/User}}
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{{Related|systemd FAQ}}
{{Article summary wiki|systemd/Services}}
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{{Related|init}}
{{Article summary wiki|systemd/cron functionality}}
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{{Related|init Rosetta}}
{{Article summary wiki|systemd FAQ}}
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{{Related|Daemons#List of daemons}}
{{Article summary wiki|init Rosetta}}
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{{Related|udev}}
{{Article summary wiki|Daemons List}}
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{{Related|Improve boot performance}}
{{Article summary wiki|udev}}
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{{Related|Allow users to shutdown}}
{{Article summary wiki|Improve Boot Performance}}
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{{Related articles end}}
{{Article summary end}}
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From the [http://freedesktop.org/wiki/Software/systemd project web page]:
 
From the [http://freedesktop.org/wiki/Software/systemd project web page]:
  
:''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|control groups]], supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic.
+
:''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 [[control groups]], supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic.
  
 
{{Note|1=For a detailed explanation as to why Arch has moved to ''systemd'', see [https://bbs.archlinux.org/viewtopic.php?pid=1149530#p1149530 this forum post].}}
 
{{Note|1=For a detailed explanation as to why Arch has moved to ''systemd'', see [https://bbs.archlinux.org/viewtopic.php?pid=1149530#p1149530 this forum post].}}
  
== Migration from SysVinit/initscripts ==
+
== Basic systemctl usage  ==
  
{{Note|
+
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 {{ic|man systemctl}} for more details.
* {{Pkg|systemd}} and {{Pkg|systemd-sysvcompat}} are both installed by default on installation media newer than [https://www.archlinux.org/news/systemd-is-now-the-default-on-new-installations/ 2012-10-13]. This section is aimed at Arch Linux installations that still rely on ''sysvinit'' and ''initscripts''.
+
* If you are running Arch Linux inside a VPS, please see [[Virtual Private Server#Moving your VPS from initscripts to systemd]].
+
}}
+
  
=== Considerations before switching ===
+
{{Tip|
 +
* 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.
 +
* ''systemadm'' is the official graphical frontend for ''systemctl''. It is provided by {{Pkg|systemd-ui}} from the [[official repositories]] or by {{AUR|systemd-ui-git}}{{Broken package link|{{aur-mirror|systemd-ui-git}}}} from the [[AUR]] for the development version.
 +
* [[Plasma]] users can install {{Pkg|systemd-kcm}} as a graphical fronted for ''systemctl''. After installing the module will be added under ''System administration''.}}
  
* Do [http://freedesktop.org/wiki/Software/systemd/ some reading] about ''systemd''.
+
=== Analyzing the system state ===
* Note the fact that systemd has a ''journal'' system that replaces ''syslog'', although the two can co-exist. See [[#Journal]].
+
* While ''systemd'' can replace some of the functionality of ''cron'', ''acpid'', or ''xinetd'', there is no need to switch away from using the traditional daemons unless you want to.
+
* Interactive ''initscripts'' are not working with ''systemd''. In particular, ''netcfg-menu'' cannot be used at system start-up ({{Bug|31377}}).
+
  
=== Installation procedure ===
+
Show '''system status''' using:
  
# [[pacman|Install]] {{Pkg|systemd}} from the [[official repositories]].
+
  $ systemctl status
# Append the following to your [[kernel parameters]]: {{ic|1=init=/usr/lib/systemd/systemd}}.
+
# Once completed you may enable any desired services via the use of {{ic|systemctl enable ''service_name''}} (this roughly equates to what you included in the {{ic|DAEMONS}} array. New names can be found in [[Daemons List]]).
+
# Reboot your system and verify that ''systemd'' is currently active by issuing the following command: {{ic|cat /proc/1/comm}}. This should return the string {{ic|systemd}}.
+
# Make sure your hostname is set correctly under ''systemd'': {{ic|hostnamectl set-hostname ''myhostname''}} or {{ic|/etc/hostname}}.
+
# Proceed to remove ''initscripts'' and ''sysvinit'' from your system and install {{Pkg|systemd-sysvcompat}}.
+
# Optionally, remove the {{ic|1=init=/usr/lib/systemd/systemd}} parameter. It is no longer needed since {{Pkg|systemd-sysvcompat}} provides a symlink to ''systemd'''s init where ''sysvinit'' used to be.
+
 
+
=== Supplementary information ===
+
 
+
* If you have {{ic|quiet}} in your kernel parameters, you might want to remove it for your first couple of systemd boots, to assist with identifying any issues during boot.
+
 
+
* It is not necessary to add your user to [[Users and Groups|groups]] ({{ic|sys}}, {{ic|disk}}, {{ic|lp}}, {{ic|network}}, {{ic|video}}, {{ic|audio}}, {{ic|optical}}, {{ic|storage}}, {{ic|scanner}}, {{ic|power}}, etc.) for most use cases with systemd. The groups can even cause some functionality to break. For example, the {{ic|audio}} group will break fast user switching and allows applications to block software mixing. Every PAM login provides a logind session, which for a local session will give you permissions via [[Wikipedia:Access control list|POSIX ACLs]] on audio/video devices, and allow certain operations like mounting removable storage via [[udisks]].
+
 
+
* See the [[Network Configuration]] article for how to set up networking targets.
+
 
+
== 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 {{ic|man 1 systemctl}} for more details.
+
 
+
{{Tip|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.}}
+
 
+
{{Note|''systemadm'' is the official graphical frontend for ''systemctl''. It is provided by the {{AUR|systemd-ui-git}} package from the [[AUR]].}}
+
 
+
=== Analyzing the system state ===
+
  
List running units:
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'''List running''' units:
  
 
  $ systemctl
 
  $ systemctl
Line 79: Line 55:
 
  $ systemctl list-units
 
  $ systemctl list-units
  
List failed units:
+
'''List failed''' units:
  
 
  $ systemctl --failed
 
  $ systemctl --failed
  
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 a list of the installed unit files with:
+
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:
  
 
  $ systemctl list-unit-files
 
  $ systemctl list-unit-files
Line 91: Line 67:
 
Units can be, for example, services (''.service''), mount points (''.mount''), devices (''.device'') or sockets (''.socket'').
 
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:
+
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:
  
* If you do not specify the suffix, systemctl will assume ''.service''. For example, {{ic|netcfg}} and {{ic|netcfg.service}} are equivalent.
+
* If you do not specify the suffix, systemctl will assume ''.service''. For example, {{ic|netctl}} and {{ic|netctl.service}} are equivalent.
 
* Mount points will automatically be translated into the appropriate ''.mount'' unit. For example, specifying {{ic|/home}} is equivalent to {{ic|home.mount}}.
 
* 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}}.
 
* 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}}.
Line 99: Line 75:
 
See {{ic|man systemd.unit}} for details.
 
See {{ic|man systemd.unit}} for details.
  
Activate a unit immediately:
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{{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.
 +
 
 +
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.
 +
}}
 +
 
 +
{{Tip|
 +
* Most of the following commands also work if multiple units are specified, see {{ic|man systemctl}} for more information.
 +
* Since [https://github.com/systemd/systemd/blob/master/NEWS#L323-L326 systemd 220], a {{ic|--now}} switch can be used in conjunction with {{ic|enable}}, {{ic|disable}} and {{ic|mask}} to respectively start, stop or mask immediately the unit rather than after the next boot.
 +
* 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.}}
 +
 
 +
'''Start''' a unit immediately:
  
 
  # systemctl start ''unit''
 
  # systemctl start ''unit''
  
Deactivate a unit immediately:
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'''Stop''' a unit immediately:
  
 
  # systemctl stop ''unit''
 
  # systemctl stop ''unit''
  
Restart a unit:
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'''Restart''' a unit:
  
 
  # systemctl restart ''unit''
 
  # systemctl restart ''unit''
  
Ask a unit to reload its configuration:
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Ask a unit to '''reload''' its configuration:
  
 
  # systemctl reload ''unit''
 
  # systemctl reload ''unit''
  
Show the status of a unit, including whether it is running or not:
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Show the '''status''' of a unit, including whether it is running or not:
  
 
  $ systemctl status ''unit''
 
  $ systemctl status ''unit''
  
Check whether a unit is already enabled or not:
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'''Check''' whether a unit is already enabled or not:
  
 
  $ systemctl is-enabled ''unit''
 
  $ systemctl is-enabled ''unit''
  
Enable a unit to be started on bootup:
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'''Enable''' a unit to be started on '''bootup''':
  
 
  # systemctl enable ''unit''
 
  # systemctl enable ''unit''
  
{{Note|Services without an {{ic|[Install]}} section are usually called automatically by other services. If you need to install them manually, use the following command, replacing ''foo'' with the name of the service.
+
'''Disable''' a unit to not start during bootup:
# ln -s /usr/lib/systemd/system/''foo''.service /etc/systemd/system/graphical.target.wants/
+
}}
+
 
+
Disable a unit to not start during bootup:
+
  
 
  # systemctl disable ''unit''
 
  # systemctl disable ''unit''
  
Show the manual page associated with a unit (this has to be supported by the unit file):
+
'''Mask''' a unit to make it impossible to start it:
 +
 
 +
# 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''
 
  $ systemctl help ''unit''
  
Reload ''systemd'', scanning for new or changed units:
+
Reload ''systemd'', scanning for '''new or changed units''':
  
 
  # systemctl daemon-reload
 
  # systemctl daemon-reload
Line 145: Line 135:
 
=== Power management ===
 
=== Power management ===
  
[[polkit]] is necessary for power management. 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.
+
[[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:
 
Shut down and reboot the system:
Line 167: Line 157:
 
  $ systemctl hybrid-sleep
 
  $ systemctl hybrid-sleep
  
== Running DMs under systemd ==
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== Writing unit files ==
  
{{Merge|Display Manager|We have separate article, this section should be moved there to keep things in one place.}}
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The syntax of ''systemd'''s [http://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 two locations. From lowest to highest precedence they are:
  
To enable graphical login, run your preferred [[Display Manager]] daemon (e.g. [[KDM]]). At the moment, service files exist for [[GDM]], [[KDM]], [[SLiM]], [[XDM]], [[LXDM]], [[LightDM]], and {{AUR|SDDM}}.
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* {{ic|/usr/lib/systemd/system/}}: units provided by installed packages
 +
* {{ic|/etc/systemd/system/}}: units installed by the system administrator
  
# systemctl enable kdm
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{{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. See {{ic|man systemd.unit}} and {{ic|man systemd-escape}} for more information.}}
  
This should work out of the box. If not, you might have a ''default.target'' set manually or from an older install:
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Look at the units installed by your packages for examples, as well as the [http://www.freedesktop.org/software/systemd/man/systemd.service.html#Examples annotated example section] of {{ic|man systemd.service}}.
  
{{hc|# ls -l /etc/systemd/system/default.target|
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{{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.}}
/etc/systemd/system/default.target -> /usr/lib/systemd/system/graphical.target}}
+
  
Simply delete the symlink and ''systemd'' will use its stock ''default.target'' (i.e. ''graphical.target'').
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=== Handling dependencies ===
  
# rm /etc/systemd/system/default.target
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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.
  
=== Using systemd-logind ===
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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.
  
In order to check the status of your user session, you can use {{ic|loginctl}}. All [[PolicyKit]] actions like suspending the system or mounting external drives will work out of the box.
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=== Service types ===
  
$ loginctl show-session $XDG_SESSION_ID
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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:
  
== Native configuration ==
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* {{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}}.
  
{{Note|You may need to create these files. All files should have {{ic|644}} permissions and {{ic|root:root}} ownership.}}
+
See the [http://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.
  
=== Virtual console ===
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=== Editing provided units ===
{{Deletion|Not strictly related, trying to remove the [[#Native configuration]] section entirely.|section=Duplication of content in Native configuration section}}
+
  
The virtual console (keyboard mapping, console font and console map) is configured in {{ic|/etc/vconsole.conf}} or by using the ''localectl'' tool.
+
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 overwrites 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 {{ic|systemctl edit}} (which reloads the unit automatically) or by reloading all units with:
  
For more information, see [[Fonts#Console fonts|console fonts]] and [[KEYMAP|keymaps]].
+
# systemctl daemon-reload
  
=== Kernel modules ===
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{{Tip|
{{Deletion|Not strictly related, trying to remove the [[#Native configuration]] section entirely.|section=Duplication of content in Native configuration section}}
+
* 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.
 +
* Syntax highlighting for ''systemd'' unit files within [[Vim]] can be enabled by installing {{Pkg|vim-systemd}}.
 +
}}
  
See [[Kernel modules#Configuration]].
+
==== Replacement unit files ====
  
=== Filesystem mounts ===
+
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:
{{Merge|File Systems|This section was added here before systemd became the default init system. Delete it after merging.|section=Duplication of content in Native configuration section}}
+
  
The default setup will automatically fsck and mount filesystems before starting services that need them to be mounted. For example, systemd automatically makes sure that remote filesystem mounts like [[NFS]] or [[Samba]] are only started after the network has been set up. Therefore, local and remote filesystem mounts specified in {{ic|/etc/fstab}} should work out of the box.
+
# systemctl reenable ''unit''
  
See {{ic|man 5 systemd.mount}} for details.
+
Alternatively, run:
  
==== Automount ====
+
# systemctl edit --full ''unit''
{{Merge|fstab|This section was added here before systemd became the default init system. Delete it after merging.|section=Duplication of content in Native configuration section}}
+
  
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 checked by ''fsck''. This can be achieved by adding the following options to the {{ic|/etc/fstab}} entry of your {{ic|/home}} partition:
+
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.
  
noauto,x-systemd.automount
+
{{Note|Pacman does not update the replacement unit files when the originals are updated, so this method can make system maintenance more difficult. For this reason the next approach is recommended.}}
  
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.
+
==== Drop-in snippets ====
  
{{Note|This will make your {{ic|/home}} filesystem type {{ic|autofs}}, which is ignored by [[mlocate]] by default. The speedup of automounting {{ic|/home}} may not be more than a second or two, depending on your system, so this trick may not be worth it.}}
+
To create drop-in snippets 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 these ''.conf'' files and apply them on top of the original unit.
  
The same applies to remote filesystem mounts. If you want them to be mounted only upon access, you will need to use the {{ic|noauto,x-systemd.automount}} parameters. In addition, you can use the {{ic|1=x-systemd.device-timeout=#}} option to specify a timeout in case the network resource is not available.
+
The easiest way to do this is to run:
  
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 does not have to wait for the device to become available. For example:
+
# systemctl edit ''unit''
  
{{hc|/etc/crypttab|
+
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.
data /dev/md0 /root/key noauto}}
+
  
==== LVM ====
+
==== Examples ====
{{Merge|LVM|This section was added here before systemd became the default init system. Delete it after merging.|section=Duplication of content in Native configuration section}}
+
  
If you have [[LVM]] volumes not activated via the [[Mkinitcpio|initramfs]], [[Systemd#Using_units|enable]] the '''lvm-monitoring''' service, which is provided by the {{pkg|lvm2}} package.
+
For example, if you simply want to add an additional dependency to a unit, you may create the following file:
 
+
=== ACPI power management ===
+
{{Deletion|Not strictly related, trying to remove the [[#Native configuration]] section entirely.|section=Duplication of content in Native configuration section}}
+
 
+
See [[Power Management]].
+
 
+
=== Temporary files ===
+
{{Moveto|Systemd#|Trying to remove the [[#Native configuration]] section entirely, this section can easily become a top-level one like [[#Journal]].|section=Duplication of content in Native configuration section}}
+
 
+
"'''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.
+
 
+
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:
+
 
+
{{hc|/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 {{ic|/etc/rc.local}} to disable wakeup from USB devices with {{ic|echo USBE > /proc/acpi/wakeup}}, you may use the following tmpfile instead:
+
 
+
{{hc|/etc/tmpfiles.d/disable-usb-wake.conf|
+
w /proc/acpi/wakeup - - - - USBE}}
+
 
+
See the {{ic|systemd-tmpfiles}} and {{ic|tmpfiles.d(5)}} man pages for details.
+
 
+
{{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 [[Modprobe.d#Configuration|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.}}
+
 
+
== Writing custom .service files ==
+
 
+
The syntax of systemd's [[#Using units|unit files]] is inspired by XDG Desktop Entry Specification .desktop files, which are in turn inspired by Microsoft Windows .ini files.
+
 
+
See [[systemd/Services]] for more examples.
+
 
+
=== 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.
+
 
+
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.
+
 
+
=== Type ===
+
 
+
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}} (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.
+
 
+
=== Editing provided unit files ===
+
 
+
To edit a unit file provided by a package, you can create a directory called {{ic|/etc/systemd/system/''unit''.d/}} for example {{ic|/etc/systemd/system/httpd.service.d/}}  and place ''*.conf'' files in there to override or add new options. ''systemd'' will parse these ''*.conf'' files and apply them on top of the original unit. For example, if you simply want to add an additional dependency to a unit, you may create the following file:
+
  
 
{{hc|/etc/systemd/system/''unit''.d/customdependency.conf|2=
 
{{hc|/etc/systemd/system/''unit''.d/customdependency.conf|2=
 
[Unit]
 
[Unit]
 
Requires=''new dependency''
 
Requires=''new dependency''
After=''new dependency''}}
+
After=''new dependency''
 +
}}
  
Then run the following for your changes to take effect:
+
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:
  
# systemctl daemon-reload
+
{{hc|/etc/systemd/system/''unit''.d/customexec.conf|2=
# systemctl restart ''unit''
+
[Service]
 +
ExecStart=
 +
ExecStart=''new command''
 +
}}
  
Alternatively you can copy the old unit file from {{ic|/usr/lib/systemd/system/}} to {{ic|/etc/systemd/system/}} and make your changes there. A unit file in {{ic|/etc/systemd/system/}} always overrides the same unit in {{ic|/usr/lib/systemd/system/}}. Note that when the original unit in {{ic|/usr/lib/}} is changed due to a package upgrade, these changes will not automatically apply to your custom unit file in {{ic|/etc/}}. Additionally you will have to manually reenable the unit with {{ic|systemctl reenable ''unit''}}. It is therefore recommended to use the ''*.conf'' method described before instead.
+
Note how {{ic|ExecStart}} must be cleared before being re-assigned ([https://bugzilla.redhat.com/show_bug.cgi?id=756787#c9]).
  
{{Tip|You can use '''systemd-delta''' to see which unit files have been overridden and what exactly has been changed.}}
+
One more example to automatically restart a service:
  
As the provided unit files will be updated from time to time, use ''systemd-delta'' for system maintenance.
+
{{hc|/etc/systemd/system/''unit''.d/restart.conf|2=
 
+
[Service]
=== Syntax highlighting for units within Vim ===
+
Restart=always
 
+
RestartSec=30
Syntax highlighting for ''systemd'' unit files within [[Vim]] can be enabled by installing {{Pkg|vim-systemd}} from the [[Official Repositories|official repositories]].
+
}}
  
 
== Targets ==
 
== Targets ==
 +
 +
{{Style|Unclear description, copy-pasted content (explicitly mentions "Fedora").|section=Make section "Targets" more clearly}}
  
 
''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 ''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.
 
''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 ''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.
Line 318: Line 269:
 
=== Create custom target ===
 
=== Create custom target ===
  
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.
+
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.
  
 
=== Targets table ===
 
=== Targets table ===
  
{| border="1"
+
{| class="wikitable"
 
! SysV Runlevel !! systemd Target !! Notes
 
! SysV Runlevel !! systemd Target !! Notes
 
|-
 
|-
Line 351: Line 302:
 
=== Change default target to boot into ===
 
=== Change default target to boot into ===
  
The standard target is ''default.target'', which is aliased by default to ''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:
+
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:
 
+
{{Tip|The ''.target'' extension can be left out.}}
+
  
 
* {{ic|1=systemd.unit=multi-user.target}} (which roughly corresponds to the old runlevel 3),
 
* {{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).
 
* {{ic|1=systemd.unit=rescue.target}} (which roughly corresponds to the old runlevel 1).
  
Alternatively, you may leave the bootloader alone and change ''default.target''. This can be done using ''systemctl'':
+
Alternatively, you may leave the bootloader alone and change {{ic|default.target}}. This can be done using ''systemctl'':
  
  # systemctl enable multi-user.target
+
  # systemctl set-default multi-user.target
  
The effect of this command is output by ''systemctl''; a symlink to the new default target is made at {{ic|/etc/systemd/system/default.target}}. This works if, and only if:
+
To be able to override the previously set {{ic|default.target}}, use the force option:
  
  [Install]
+
  # systemctl set-default -f multi-user.target
Alias=default.target
+
  
is in the target's configuration file. Currently, ''multi-user.target'' and ''graphical.target'' both have it.
+
The effect of this command is output by ''systemctl''; a symlink to the new default target is made at {{ic|/etc/systemd/system/default.target}}.
 +
 
 +
== Temporary files ==
 +
 
 +
"''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.
 +
 
 +
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:
 +
 
 +
{{hc|/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 {{ic|/etc/rc.local}} to disable wakeup from USB devices with {{ic|echo USBE > /proc/acpi/wakeup}}, you may use the following tmpfile instead:
 +
 
 +
{{hc|/etc/tmpfiles.d/disable-usb-wake.conf|
 +
w /proc/acpi/wakeup - - - - USBE}}
 +
 
 +
See the {{ic|systemd-tmpfiles(8)}} and {{ic|tmpfiles.d(5)}} man pages for details.
 +
 
 +
{{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.}}
  
 
== Timers ==
 
== Timers ==
  
Systemd can replace cron functionality to a great extent. For further information, please refer to [[systemd/cron functionality]].
+
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]].}}
  
 
== Journal ==
 
== Journal ==
  
''systemd'' has its own logging system called the journal; therefore, running a syslog daemon is no longer required. To read the log, use:
+
''systemd'' has its own logging system called the journal; therefore, running a {{ic|syslog}} daemon is no longer required. To read the log, use:
  
 
  # journalctl
 
  # journalctl
  
By default (when {{ic|1=Storage=}} is set to {{ic|auto}} in {{ic|/etc/systemd/journald.conf}}), the journal writes to {{ic|/var/log/journal/}}. The directory {{ic|/var/log/journal/}} is a part of the ''systemd'' package. If you or some program delete that directory, systemd will '''not''' recreate it automatically; however, it will be recreated during the next update of the systemd package. Until then, logs will be written to {{ic|/run/systemd/journal}}, and logs will be lost on reboot.
+
In Arch Linux, the directory {{ic|/var/log/journal/}} is a part of the {{Pkg|systemd}} package, and the journal (when {{ic|1=Storage=}} is set to {{ic|auto}} in {{ic|/etc/systemd/journald.conf}}) will write to {{ic|/var/log/journal/}}. If you or some program delete that directory, ''systemd'' will '''not''' recreate it automatically and instead will write its logs to {{ic|/run/systemd/journal}} in a nonpersistent way. However, the folder will be recreated when you set {{ic|1=Storage=persistent}} and run {{ic|systemctl restart systemd-journald}} (or reboot).
 
+
{{Tip|If {{ic|/var/log/journal/}} resides in a [[btrfs]] filesystem you should consider disabling [[Btrfs#Copy-On-Write_.28CoW.29|Copy-on-Write]] for the directory:
+
# chattr +C /var/log/journal
+
}}
+
  
 
=== Filtering output ===
 
=== Filtering output ===
  
''journalctl'' allows you to filter the output by specific fields.
+
''journalctl'' allows you to filter the output by specific fields. Be aware that if there are many messages to display or filtering of large time span has to be done, the output of this command can be delayed for quite some time.
 +
 
 +
{{Tip|While the journal is stored in a binary format, the content of stored messages is not modified. This means it is viewable with ''strings'', for example for recovery in an environment which does not have ''systemd'' installed. Example command:
 +
{{bc|$ strings /mnt/arch/var/log/journal/af4967d77fba44c6b093d0e9862f6ddd/system.journal <nowiki>| grep -i</nowiki> ''message''}}
 +
}}
  
 
Examples:
 
Examples:
  
Show all messages from this boot:
+
* Show all messages from this boot: {{bc|# journalctl -b}} However, often one is interested in messages not from the current, but from the previous boot (e.g. if an unrecoverable system crash happened). This is possible through optional offset parameter of the {{ic|-b}} flag: {{ic|journalctl -b -0}} shows messages from the current boot, {{ic|journalctl -b -1}} from the previous boot, {{ic|journalctl -b -2}} from the second previous and so on. See {{ic|man 1 journalctl}} for full description, the semantics is much more powerful.
+
* Show all messages from date (and optional time): {{bc|1=# journalctl --since="2012-10-30 18:17:16"}}
# journalctl -b
+
* Show all messages since 20 minutes ago: {{bc|1=# journalctl --since "20 min ago"}}
 +
* Follow new messages: {{bc|# journalctl -f}}
 +
* Show all messages by a specific executable: {{bc|# journalctl /usr/lib/systemd/systemd}}
 +
* Show all messages by a specific process: {{bc|1=# journalctl _PID=1}}
 +
* Show all messages by a specific unit: {{bc|# journalctl -u netcfg}}
 +
* Show kernel ring buffer: {{bc|1=# journalctl -k}}
 +
* Show auth.log equivalent by filtering on syslog facility: {{bc|1=# journalctl -f -l SYSLOG_FACILITY=10}}
  
However, often one is interested in messages not from the current, but from the previous boot (e.g. if an unrecoverable system crash happened). Currently, this feature is not implemented, though there was a discussion at [http://comments.gmane.org/gmane.comp.sysutils.systemd.devel/6608 systemd-devel@lists.freedesktop.org] (September/October 2012).
+
See {{ic|man 1 journalctl}}, {{ic|man 7 systemd.journal-fields}}, or Lennart's [http://0pointer.de/blog/projects/journalctl.html blog post] for details.
  
As a workaround you can use at the moment:
+
{{Tip|1=
 +
By default, ''journalctl'' truncates lines longer than screen width, but in some cases, it may be better to enable wrapping instead of truncating. This can be controlled by the {{ic|SYSTEMD_LESS}} [[environment variable]], which contains options passed to [[Core utilities#less|less]] (the default pager) and defaults to {{ic|FRSXMK}} (see {{ic|man 1 less}} and {{ic|man 1 journalctl}} for details).
  
# journalctl --since=today | tac | sed -n '/-- Reboot --/{n;:r;/-- Reboot --/q;p;n;b r}' | tac
+
By omitting the {{ic|S}} option, the output will be wrapped instead of truncated. For example, start ''journalctl'' as follows:
  
provided, that the previous boot happened today. Be aware that, if there are many messages for the current day, the output of this command can be delayed for quite some time.
+
  $ SYSTEMD_LESS=FRXMK journalctl
{{note|This needs to be corrected once 206 lands. {{ic|journalctl -b}} now takes arguments such as {{ic|-0}} for the last boot or a boot id. E.g. {{ic|journalctl -b -3}} will show all messages from the fourth to last boot.}}
+
  
Follow new messages:
+
If you would like to set this behaviour as default, [[Environment variables#Per_user|export]] the variable from {{ic|~/.bashrc}} or {{ic|~/.zshrc}}.
 +
}}
  
# journalctl -f
+
=== Journal size limit ===
  
Show all messages by a specific executable:
+
If the journal is persistent (non-volatile), its size limit is set to a default value of 10% of the size of the respective file system. For example, 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 uncommenting and changing the following:
  
# journalctl /usr/lib/systemd/systemd
+
{{hc|/etc/systemd/journald.conf|2=
 +
SystemMaxUse=50M
 +
}}
  
Show all messages by a specific process:
+
Refer to {{ic|man journald.conf}} for more info.
  
# journalctl _PID=1
+
=== Clean journal files manually ===
  
Show all messages by a specific unit:
+
The journal files are located under {{ic|/var/log/journal}}, {{ic|rm}} will do the work.
 +
Or, use {{ic|journalctl}},
  
# journalctl -u netcfg
+
Examples:
  
See {{ic|man 1 journalctl}}, {{ic|man 7 systemd.journal-fields}}, or Lennert's [http://0pointer.de/blog/projects/journalctl.html blog post] for details.
+
* Remove archived journal files until the disk space they use falls below 100M: {{bc|1=# journalctl --vacuum-size=100M}}
 +
* Make all journal files contain no data older than 2 weeks. {{bc|1=# journalctl --vacuum-time=2weeks}}
  
=== Journal size limit ===
+
Refer to {{ic|man journalctl}} for more info.
  
If the journal is persistent (non-volatile), its size limit is set to a default value of 10% of the size of the respective file system. For example, 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:
+
=== Journald in conjunction with syslog ===
  
SystemMaxUse=50M
+
Compatibility with a classic, non-journald aware [[Syslog-ng|syslog]] implementation can be provided by letting ''systemd'' forward all messages via the socket {{ic|/run/systemd/journal/syslog}}. 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]).
  
Refer to {{ic|man journald.conf}} for more info.
+
As of ''systemd'' 216 the default {{ic|journald.conf}} for forwarding to the socket was changed to {{ic|1=ForwardToSyslog=no}} to avoid system overhead, because [[rsyslog]] or [[syslog-ng]] (since 3.6) pull the messages from the journal by [http://lists.freedesktop.org/archives/systemd-devel/2014-August/022295.html#journald itself].  
  
=== Journald in conjunction with syslog ===
+
See [[Syslog-ng#Overview]] and [[Syslog-ng#syslog-ng and systemd journal]], or [[rsyslog]] respectively, for details on configuration.
  
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]). The {{Pkg|syslog-ng}} package in the repositories automatically provides the necessary configuration.
+
=== Forward journald to /dev/tty12 ===
  
# systemctl enable syslog-ng
+
Create a [[#Editing provided units|drop-in directory]] {{ic|/etc/systemd/journald.conf.d}} and create a {{ic|fw-tty12.conf}} file in it:
  
A good ''journalctl'' tutorial is [http://0pointer.de/blog/projects/journalctl.html here].
+
{{hc|1=/etc/systemd/journald.conf.d/fw-tty12.conf|2=
 +
[Journal]
 +
ForwardToConsole=yes
 +
TTYPath=/dev/tty12
 +
MaxLevelConsole=info
 +
}}
 +
 
 +
Then [[restart]] systemd-journald.
 +
 
 +
=== Specify a different journal to view ===
 +
There may be a need to check the logs of another system that is dead in the water, like booting from a live system to recover a production system. In such case, one can mount the disk in e.g. {{ic|/mnt}}, and specify the journal path via {{ic|-D}}/{{ic|--directory}}, like so:
 +
 
 +
$ journalctl -D ''/mnt''/var/log/journal -xe
  
 
== Troubleshooting ==
 
== Troubleshooting ==
  
=== Shutdown/reboot takes terribly long ===
+
=== Investigating systemd errors ===
  
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].
+
As an example, we will investigate an error with {{ic|systemd-modules-load}} service:
  
=== Short lived processes do not seem to log any output ===
+
'''1.''' Lets find the ''systemd'' services which fail to start:
 +
 
 +
{{hc|1=$ systemctl --failed|2=
 +
systemd-modules-load.service  loaded '''failed failed'''  Load Kernel Modules
 +
}}
 +
 
 +
'''2.''' Ok, we found a problem with {{ic|systemd-modules-load}} service. We want to know more:
 +
{{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}}
 +
 
 +
'''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):
 +
{{hc|1=$ journalctl _PID=15630|2=
 +
-- 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 {{ic|/etc/modules-load.d/}}:
 +
{{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
 +
...
 +
}}
 +
 
 +
'''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:
 +
{{hc|/etc/modules-load.d/blacklist.conf|
 +
'''#''' blacklist usblp
 +
'''#''' install usblp /bin/false
 +
}}
 +
 
 +
'''6.''' Now, try to start {{ic|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:
 +
{{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'''.
 +
}}
  
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 _SYSTEMD_UNIT and _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 SCM_CREDENTIALS.
+
Often you can solve these kind of problems like shown above. For further investigation look at [[#Diagnosing boot problems]].
  
 
=== Diagnosing boot problems ===
 
=== Diagnosing boot problems ===
  
Boot with these parameters on the kernel command line:
+
''systemd'' has several options for diagnosing problems with the boot process. See [[boot debugging]] and the [http://freedesktop.org/wiki/Software/systemd/Debugging/ systemd debugging documentation].
{{ic|<nowiki>systemd.log_level=debug systemd.log_target=kmsg log_buf_len=1M</nowiki>}}
+
  
[http://freedesktop.org/wiki/Software/systemd/Debugging More Debugging Information]
+
=== Diagnosing problems with a specific service ===
 +
 
 +
{{Accuracy|This may not catch all errors such as missing libraries.|User talk:Alucryd#Plex}}
 +
 
 +
If some ''systemd'' service misbehaves and you want to get more information about what is going on, set the {{ic|SYSTEMD_LOG_LEVEL}} [[environment variable]] to {{ic|debug}}. For example, to run the ''systemd-networkd'' daemon in debug mode:
 +
 
 +
# systemctl stop systemd-networkd
 +
# SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd
 +
 
 +
Or, equivalently, modify the service file temporarily for gathering enough output. For example:
 +
 
 +
{{hc|/usr/lib/systemd/system/systemd-networkd.service|2=
 +
[Service]
 +
...
 +
Environment=SYSTEMD_LOG_LEVEL=debug
 +
....
 +
}}
 +
 
 +
If debug information is required long-term, add the variable the [[#Editing provided units|regular]] way.
 +
 
 +
=== 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/#shutdowncompleteseventually this article].
 +
 
 +
=== Short lived processes do not seem to log any output ===
 +
 
 +
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}}.
  
 
=== Disabling application crash dumps journaling ===
 
=== Disabling application crash dumps journaling ===
  
Run the following in order to overwrite the settings from {{ic|/lib/sysctl.d/}}:
+
Edit the file {{ic|/etc/systemd/coredump.conf}} by adding this line:
  # ln -s /dev/null /etc/sysctl.d/50-coredump.conf
+
 
# sysctl kernel.core_pattern=core
+
  Storage=none
 +
 
 +
and run:
 +
 
 +
  # systemctl daemon-reload
 +
 
 +
to reload the configuration.
 +
 
 +
=== Boot time increasing over time ===
 +
 
 +
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.
 +
 
 +
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 [[#Journal size limit]].
 +
 
 +
=== systemd-tmpfiles-setup.service fails to start at boot ===
 +
 
 +
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.
 +
 
 +
See [[Access Control Lists#Enabling ACL]] for instructions on how to enable ACL on the filesystem that houses {{ic|/var/log/journal}}.
 +
 
 +
=== systemctl enable fails for symlinks in /etc/systemd/system ===
 +
 
 +
If {{ic|/etc/systemd/system/''foo''.service}} is a symlink and {{ic|systemctl enable ''foo''.service}} is run, it will fail with this error:
  
This will disable logging of coredumps to the journal.
+
Failed to issue method call: No such file or directory
  
Note that the default RLIMIT_CORE of 0 means that no core files are written, either.
+
This is a [https://bugzilla.redhat.com/show_bug.cgi?id=955379#c14 design choice] of systemd. As a workaround, enabling by absolute path works:
If you want them, you also need to "unlimit" the core file size in the shell:
+
$ ulimit -c unlimited
+
  
See [http://www.freedesktop.org/software/systemd/man/sysctl.d.html sysctl.d] and [https://www.kernel.org/doc/Documentation/sysctl/kernel.txt the documentation for /proc/sys/kernel] for more information.
+
# systemctl enable ''/absolute/path/foo''.service
  
 
== See also ==
 
== See also ==
Line 487: Line 577:
 
*[http://0pointer.de/blog/projects/why.html Most recent summary]
 
*[http://0pointer.de/blog/projects/why.html Most recent summary]
 
*[http://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet Fedora's SysVinit to systemd cheatsheet]
 
*[http://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet Fedora's SysVinit to systemd cheatsheet]
 +
*[http://wiki.gentoo.org/wiki/Systemd Gentoo Wiki systemd page]
 +
*[[Emacs#Syntax highlighting for systemd Files|Emacs Syntax highlighting for Systemd files]]

Latest revision as of 12:57, 7 April 2016

From the project web page:

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 control groups, supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic.
Note: For a detailed explanation as to why Arch has 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 man systemctl 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.
  • systemadm is the official graphical frontend for systemctl. It is provided by systemd-ui from the official repositories or by systemd-ui-gitAUR[broken link: archived in aur-mirror] from the AUR for the development version.
  • Plasma users can install systemd-kcm as a graphical fronted 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

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 man systemd.unit 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 man systemctl for more information.
  • Since systemd 220, a --now switch can be used in conjunction with enable, disable and mask to respectively start, stop or mask immediately the unit rather than after the next boot.
  • 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

Disable a unit to not start during bootup:

# systemctl disable unit

Mask a unit to make it impossible to start it:

# 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, scanning for new or changed units:

# 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 two locations. From lowest to highest precedence they are:

  • /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. See man systemd.unit and man systemd-escape for more information.

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

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

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 overwrites 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.
  • Syntax highlighting for systemd unit files within Vim can be enabled by installing vim-systemd.

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: Pacman does not update the replacement unit files when the originals are updated, so this method can make system maintenance more difficult. For this reason the next approach is recommended.

Drop-in snippets

To create drop-in snippets 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 these .conf files and apply them 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.

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]).

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.Tango-edit-clear.png

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

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 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.

Targets table

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 aliased by default to 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:

  • 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).

Alternatively, you may leave the bootloader alone and change default.target. This can be done using systemctl:

# systemctl set-default multi-user.target

To be able to override the previously set default.target, use the force option:

# systemctl set-default -f multi-user.target

The effect of this command is output by systemctl; a symlink to the new default target is made at /etc/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
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.

Journal

systemd has its own logging system called the journal; therefore, running a syslog daemon is no longer required. To read the log, use:

# journalctl

In Arch Linux, the directory /var/log/journal/ is a part of the systemd package, and the journal (when Storage= is set to auto in /etc/systemd/journald.conf) will write to /var/log/journal/. If you or some program delete that directory, systemd will not recreate it automatically and instead will write its logs to /run/systemd/journal in a nonpersistent way. However, the folder will be recreated when you set Storage=persistent and run systemctl restart systemd-journald (or reboot).

Filtering output

journalctl allows you to filter the output by specific fields. Be aware that if there are many messages to display or filtering of large time span has to be done, the output of this command can be delayed for quite some time.

Tip: While the journal is stored in a binary format, the content of stored messages is not modified. This means it is viewable with strings, for example for recovery in an environment which does not have systemd installed. Example command:
$ strings /mnt/arch/var/log/journal/af4967d77fba44c6b093d0e9862f6ddd/system.journal | grep -i message

Examples:

  • Show all messages from this boot:
    # journalctl -b
    However, often one is interested in messages not from the current, but from the previous boot (e.g. if an unrecoverable system crash happened). This is possible through optional offset parameter of the -b flag: journalctl -b -0 shows messages from the current boot, journalctl -b -1 from the previous boot, journalctl -b -2 from the second previous and so on. See man 1 journalctl for full description, the semantics is much more powerful.
  • Show all messages from date (and optional time):
    # journalctl --since="2012-10-30 18:17:16"
  • Show all messages since 20 minutes ago:
    # journalctl --since "20 min ago"
  • Follow new messages:
    # journalctl -f
  • Show all messages by a specific executable:
    # journalctl /usr/lib/systemd/systemd
  • Show all messages by a specific process:
    # journalctl _PID=1
  • Show all messages by a specific unit:
    # journalctl -u netcfg
  • Show kernel ring buffer:
    # journalctl -k
  • Show auth.log equivalent by filtering on syslog facility:
    # journalctl -f -l SYSLOG_FACILITY=10

See man 1 journalctl, man 7 systemd.journal-fields, or Lennart's blog post for details.

Tip: By default, journalctl truncates lines longer than screen width, but in some cases, it may be better to enable wrapping instead of truncating. This can be controlled by the SYSTEMD_LESS environment variable, which contains options passed to less (the default pager) and defaults to FRSXMK (see man 1 less and man 1 journalctl for details).

By omitting the S option, the output will be wrapped instead of truncated. For example, start journalctl as follows:

$ SYSTEMD_LESS=FRXMK journalctl
If you would like to set this behaviour as default, export the variable from ~/.bashrc or ~/.zshrc.

Journal size limit

If the journal is persistent (non-volatile), its size limit is set to a default value of 10% of the size of the respective file system. For example, with /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 uncommenting and changing the following:

/etc/systemd/journald.conf
SystemMaxUse=50M

Refer to man journald.conf for more info.

Clean journal files manually

The journal files are located under /var/log/journal, rm will do the work. Or, use journalctl,

Examples:

  • Remove archived journal files until the disk space they use falls below 100M:
    # journalctl --vacuum-size=100M
  • Make all journal files contain no data older than 2 weeks.
    # journalctl --vacuum-time=2weeks

Refer to man journalctl for more info.

Journald in conjunction with syslog

Compatibility with a classic, non-journald aware syslog implementation can be provided by letting systemd forward all messages via the socket /run/systemd/journal/syslog. To make the syslog daemon work with the journal, it has to bind to this socket instead of /dev/log (official announcement).

As of systemd 216 the default journald.conf for forwarding to the socket was changed to ForwardToSyslog=no to avoid system overhead, because rsyslog or syslog-ng (since 3.6) pull the messages from the journal by itself.

See Syslog-ng#Overview and Syslog-ng#syslog-ng and systemd journal, or rsyslog respectively, for details on configuration.

Forward journald to /dev/tty12

Create a drop-in directory /etc/systemd/journald.conf.d and create a fw-tty12.conf file in it:

/etc/systemd/journald.conf.d/fw-tty12.conf
[Journal]
ForwardToConsole=yes
TTYPath=/dev/tty12
MaxLevelConsole=info

Then restart systemd-journald.

Specify a different journal to view

There may be a need to check the logs of another system that is dead in the water, like booting from a live system to recover a production system. In such case, one can mount the disk in e.g. /mnt, and specify the journal path via -D/--directory, like so:

$ journalctl -D /mnt/var/log/journal -xe

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:

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

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.

Often you can solve these kind of problems like shown above. For further investigation look at #Diagnosing boot problems.

Diagnosing boot problems

systemd has several options for diagnosing problems with the boot process. See boot debugging and the systemd debugging documentation.

Diagnosing problems with a specific service

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: This may not catch all errors such as missing libraries. (Discuss in User talk:Alucryd#Plex)

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

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

Or, equivalently, modify the service file temporarily for gathering enough output. For example:

/usr/lib/systemd/system/systemd-networkd.service
[Service]
...
Environment=SYSTEMD_LOG_LEVEL=debug
....

If debug information is required long-term, add the variable the regular way.

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.

Disabling application crash dumps journaling

Edit the file /etc/systemd/coredump.conf by adding this line:

 Storage=none

and run:

# systemctl daemon-reload

to reload the configuration.

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 #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.

systemctl enable fails for symlinks in /etc/systemd/system

If /etc/systemd/system/foo.service is a symlink and systemctl enable foo.service is run, it will fail with this error:

Failed to issue method call: No such file or directory

This is a design choice of systemd. As a workaround, enabling by absolute path works:

# systemctl enable /absolute/path/foo.service

See also