systemd
Related articles
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.
Contents
- 1 Basic systemctl usage
- 2 Writing unit files
- 3 Targets
- 4 Temporary files
- 5 Timers
- 6 Mounting
- 7 Journal
- 8 Tips and tricks
-
9 Troubleshooting
- 9.1 Investigating systemd errors
- 9.2 Diagnosing boot problems
- 9.3 Diagnosing problems with a specific service
- 9.4 Shutdown/reboot takes terribly long
- 9.5 Short lived processes do not seem to log any output
- 9.6 Boot time increasing over time
- 9.7 systemd-tmpfiles-setup.service fails to start at boot
- 9.8 systemctl enable fails for symlinks in /etc/systemd/system
- 9.9 dependent services are not started when starting a service manually
- 9.10 systemd version printed on boot is not the same as installed package version
- 10 See also
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.
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
andnetctl.service
are equivalent. - Mount points will automatically be translated into the appropriate .mount unit. For example, specifying
/home
is equivalent tohome.mount
. - Similar to mount points, devices are automatically translated into the appropriate .device unit, therefore specifying
/dev/sda2
is equivalent todev-sda2.device
.
See man systemd.unit
for details.
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
Look at the units installed by your packages for examples, as well as the annotated example section of man systemd.service
.
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 specifyPIDFile=
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 setRemainAfterExit=yes
as well so that systemd still considers the service as active after the process has exited. -
Type=notify
: identical toType=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 specifiedBusName
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 toType=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 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
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.
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 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]. 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
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.
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.
Mounting
Since systemd is a replacement for System V init, it is in charge of the mounts specified in /etc/fstab
. In fact, it goes beyond the usual fstab
capabilities, implementing special mount options prefixed with x-systemd.
. See Fstab#Automount with systemd for an example of automounting (mounting on-demand) using these extensions. See [2] for the complete documentation of these extensions.
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).
Systemd journal classifies messages by Priority level and Facility. Logging classification corresponds to classic Syslog protocol (RFC 5424).
Priority level
A syslog severity code (in systemd called priority) is used to mark the importance of a message RFC 5424 Section 6.2.1.
Value | Severity | Keyword | Description | Examples |
---|---|---|---|---|
0 | Emergency | emerg | System is unusable | Severe Kernel BUG, systemd dumped core. This level should not be used by applications. |
1 | Alert | alert | Should be corrected immediately | Vital subsystem goes out of work. Data loss. kernel: BUG: unable to handle kernel paging request at ffffc90403238ffc .
|
2 | Critical | crit | Critical conditions | Crashes, coredumps. Like familiar flash:systemd-coredump[25319]: Process 25310 (plugin-containe) of user 1000 dumped core Failure in the system primary application, like X11. |
3 | Error | err | Error conditions | Not severe error reported:kernel: usb 1-3: 3:1: cannot get freq at ep 0x84 ,systemd[1]: Failed unmounting /var. ,libvirtd[1720]: internal error: Failed to initialize a valid firewall backend ).
|
4 | Warning | warning | May indicate that an error will occur if action is not taken. | A non-root file system has only 1GB free.org.freedesktop. Notifications[1860]: (process:5999): Gtk-WARNING **: Locale not supported by C library. Using the fallback 'C' locale .
|
5 | Notice | notice | Events that are unusual, but not error conditions. | systemd[1]: var.mount: Directory /var to mount over is not empty, mounting anyway . gcr-prompter[4997]: Gtk: GtkDialog mapped without a transient parent. This is discouraged .
|
6 | Informational | info | Normal operational messages that require no action. | lvm[585]: 7 logical volume(s) in volume group "archvg" now active .
|
7 | Debug | debug | Information useful to developers for debugging the application. | kdeinit5[1900]: powerdevil: Scheduling inhibition from ":1.14" "firefox" with cookie 13 and reason "screen" .
|
If issue you are looking for, was not found on according level, search it on couple of priority levels above and below. This rules are recommendations. Some errors considered a normal occasion for program so they marked low in priority by developer, and on the contrary, sometimes too many messages plaques too high priorities for them, but often it's an arguable situation. And often you really should solve an issue, also to understand architecture and adopt best practices.
Examples:
- Info message:
pulseaudio[2047]: W: [pulseaudio] alsa-mixer.c: Volume element Master has 8 channels. That's too much! I can't handle that!
It is an warning or error by definition. - Plaguing alert message:
sudo[21711]: user : a password is required ; TTY=pts/0 ; PWD=/home/user ; USER=root ; COMMAND=list /usr/bin/pacman --color auto -Sy
The reason - user was manually added to sudoers file, not to wheel group, which is arguably normal action, but sudo produced an alert on every occasion.
Facility
A syslog facility code is used to specify the type of program that is logging the message RFC 5424 Section 6.2.1.
Facility code | Keyword | Description | Info |
---|---|---|---|
0 | kern | kernel messages | |
1 | user | user-level messages | |
2 | mail system | Archaic POSIX still supported and sometimes used system, for more man mail )
|
|
3 | daemon | system daemons | All deamons, including systemd and its subsystems |
4 | auth | security/authorization messages | Also watch for different facility 10 |
5 | syslog | messages generated internally by syslogd | As it standartized for syslogd, not used by systemd (see facility 3) |
6 | lpr | line printer subsystem (archaic subsystem) | |
7 | news | network news subsystem (archaic subsystem) | |
8 | uucp | UUCP subsystem (archaic subsystem) | |
9 | clock daemon | systemd-timesyncd | |
10 | authpriv | security/authorization messages | Also watch for different facility 4 |
11 | ftp | FTP daemon | |
12 | - | NTP subsystem | |
13 | - | log audit | |
14 | - | log alert | |
15 | cron | scheduling daemon | |
16 | local0 | local use 0 (local0) | |
17 | local1 | local use 1 (local1) | |
18 | local2 | local use 2 (local2) | |
19 | local3 | local use 3 (local3) | |
20 | local4 | local use 4 (local4) | |
21 | local5 | local use 5 (local5) | |
22 | local6 | local use 6 (local6) | |
23 | local7 | local use 7 (local7) |
So, useful facilities to watch: 0,1,3,4,9,10,15.
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.
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. Seeman 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 only error, critical, and alert priority messages
# journalctl -p err..alert
Numbers also can be used,journalctl -p 3..1
. If single number/keyword used,journalctl -p 3
- all higher priority levels also included. - Show auth.log equivalent by filtering on syslog facility:
# journalctl SYSLOG_FACILITY=10
See man 1 journalctl
, man 7 systemd.journal-fields
, or Lennart's blog post for details.
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 underlying file system but capped to 4 GiB. For example, with /var/log/journal/
located on a 20 GiB partition, journal data may take up to 2 GiB. On a 50 GiB partition, it would max at 4 GiB.
The maximum size of the persistent journal can be controlled by uncommenting and changing the following:
/etc/systemd/journald.conf
SystemMaxUse=50M
It is also possible to use the drop-in snippets configuration override mechanism rather than editing the global configuration file. In this case do not forget to place the overrides under the [Journal]
header:
/etc/systemd/journald.conf.d/00-journal-size.conf
[Journal] SystemMaxUse=50M
See man journald.conf
for more info.
Clean journal files manually
Journal files can be globally removed from /var/log/journal/
using e.g. rm
, or can be trimmed according to various criteria using 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
See 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).
The default journald.conf
for forwarding to the socket is ForwardToSyslog=no
to avoid system overhead, because rsyslog or syslog-ng 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
Tips and tricks
Enable installed units by default
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 the manpage for systemd.preset
for more information.
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
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
.
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
dependent services are not started when starting a service manually
One (in)famous example is libvirtd.service
which needs the virtlogd.socket
to function properly.
The dependencies in /usr/lib/systemd/system/libvirtd.service
are defined as
[Install] WantedBy=multi-user.target Also=virtlockd.socket Also=virtlogd.socket
This only defines the necessary/dependent sockets to be enabled services(i.e. as "autostart"), too - but does not start them whenever the DISABLED (= non-autostarting) service ist started manually e.g. by running systemctl start libvirtd
Thus the correct (?) way to manually start a service with dependent subservices once (instead of at each start of the system) probably is
systemctl enable ServiceWithSubservices systemctl start ServiceWithSubservices systemctl disable ServiceWithSubservices
systemd version printed on boot is not the same as installed package version
You need to regenerate your initramfs and the versions should match.
See also
- Official web site
- Wikipedia article
- Manual pages
- systemd optimizations
- FAQ
- Tips and tricks
- systemd for Administrators (PDF)
- About systemd on Fedora Project
- How to debug systemd problems
- Two part introductory article in The H Open magazine.
- Lennart's blog story
- Status update
- Status update2
- Status update3
- Most recent summary
- Fedora's SysVinit to systemd cheatsheet
- Gentoo Wiki systemd page
- Emacs Syntax highlighting for Systemd files
- digital ocean tutorial