Difference between revisions of "Systemd"
(→ACPI power management) |
m (→ACPI power management) |
||
Line 209: | Line 209: | ||
{{Note|Systemd can also use other suspend backends (such as [[Uswsusp]] or [[TuxOnIce]]), in addition to the default ''kernel'' backend, in order to put the computer to sleep or hibernate.}} | {{Note|Systemd can also use other suspend backends (such as [[Uswsusp]] or [[TuxOnIce]]), in addition to the default ''kernel'' backend, in order to put the computer to sleep or hibernate.}} | ||
− | For {{ic|systemctl hibernate}} to work on your system you need to follow instructions at [[Pm-utils#Hibernation_.28suspend2disk.29|Hibernation]] and possibly at [[Pm-utils#Mkinitcpio_Resume_Hook| | + | For {{ic|systemctl hibernate}} to work on your system you need to follow instructions at [[Pm-utils#Hibernation_.28suspend2disk.29|Hibernation]] and possibly at [[Pm-utils#Mkinitcpio_Resume_Hook|Mkinitcpio Resume Hook]] ({{ic|pm-utils}} does not need to be installed.) |
==== Sleep hooks ==== | ==== Sleep hooks ==== |
Revision as of 09:30, 23 April 2013
zh-CN:Systemd zh-TW:Systemd Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary wiki Template:Article summary wiki Template:Article summary wiki Template:Article summary wiki Template:Article summary end 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. It can work as a drop-in replacement for sysvinit.
See also the Wikipedia article.
Contents
- 1 Considerations before switching
- 2 Installation
- 3 Native configuration
- 4 Basic systemctl usage
- 5 Running DEs under systemd
- 6 Writing custom .service files
- 7 Targets
- 8 Journal
- 9 Optimization
- 10 Troubleshooting
- 11 See also
Considerations before switching
- Do some reading about systemd.
- Note the fact that systemd has a journal system that replaces syslog, although the two can co-exist. See the section on the journal below.
- 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.
Installation
The following section is aimed at Arch Linux installations that still rely on sysvinit and initscripts which have not migrated to systemd.
- Install systemd and append the following to your kernel parameters:
init=/usr/lib/systemd/systemd
- Once completed you may enable any desired services via the use of
systemctl enable <service_name>
(this roughly equates to what you included in theDAEMONS
array. New names can be found here). - Reboot your system and verify that
systemd
is currently active by issuing the following command:cat /proc/1/comm
. This should return the stringsystemd
. - Make sure your hostname is set correctly under systemd:
hostnamectl set-hostname myhostname
. - Proceed to remove initscripts and sysvinit from your system and install systemd-sysvcompat.
- Optionally, remove the
init=/usr/lib/systemd/systemd
parameter as it is no longer needed. systemd-sysvcompat provides the default init.
Supplementary information
- If you have
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.
- Adding your user to groups (
sys
,disk
,lp
,network
,video
,audio
,optical
,storage
,scanner
,power
, etc.) is not necessary for most use cases with systemd. The groups can even cause some functionality to break. For example, theaudio
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 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.
Native configuration
644
permissions and root:root
ownership.Locale
/etc/locale.gen
and then executing locale-gen
as root. The locale set via localectl
must be one of the uncommented locales in /etc/locale.gen
.The default system locale is configured in /etc/locale.conf
. To set the default locale, do:
# localectl set-locale LANG="de_DE.utf8"
See man 1 localectl
and man 5 locale.conf
for details.
- For more information, see Locale.
Here is an example file:
/etc/locale.conf
LANG=en_US.utf8
Virtual console
The virtual console (keyboard mapping, console font and console map) is configured in /etc/vconsole.conf
:
/etc/vconsole.conf
KEYMAP=us FONT=lat9w-16 FONT_MAP=8859-1_to_uni
KEYMAP=
and FONT=
are empty or not set.Another way to set the keyboard mapping (keymap) is doing:
# localectl set-keymap de
localectl
can also be used to set the X11 keymap:
# localectl set-x11-keymap de
See man 1 localectl
and man 5 vconsole.conf
for details.
- For more information, see console fonts and keymaps.
Hardware clock
Systemd will use UTC for the hardware clock by default.
Hardware clock in localtime
If you want to change the hardware clock to use local time (STRONGLY DISCOURAGED) do:
# timedatectl set-local-rtc true
If you want to revert to the hardware clock being in UTC, do:
# timedatectl set-local-rtc false
Be warned that, if the hardware clock is set to localtime, dealing with daylight saving time is messy. If the DST changes when your computer is off, your clock will be wrong on next boot (there is a lot more to it). Recent kernels set the system time from the RTC directly on boot, assuming that the RTC is in UTC. This means that if the RTC is in local time, then the system time will first be set up wrongly and then corrected shortly afterwards on every boot. This is the root of certain weird bugs (time going backwards is rarely a good thing).
One reason for allowing the RTC to be in local time is to allow dual boot with Windows (which uses localtime). However, Windows is able to deal with the RTC being in UTC with a simple registry fix. It is recommended to configure Windows to use UTC, rather than Linux to use localtime. If you make Windows use UTC, also remember to disable the "Internet Time Update" Windows feature, so that Windows don't mess with the hardware clock, trying to sync it with internet time. You should instead leave touching the RTC and syncing it to internet time to Linux, by enabling an NTP daemon, as suggested previously.
- For more information, see Time.
Kernel modules
Today, all necessary module loading is handled automatically by udev, so that, if you don't want/need to use any out-of-tree kernel modules, there is no need to put modules that should be loaded at boot in any config file. However, there are cases where you might want to load an extra module during the boot process, or blacklist another one for your computer to function properly.
Extra modules to load at boot
Extra kernel modules to be loaded during boot are configured as a static list in files under /etc/modules-load.d/
. Each configuration file is named in the style of /etc/modules-load.d/<program>.conf
. Configuration files simply contain a list of kernel module names to load, separated by newlines. Empty lines and lines whose first non-whitespace character is #
or ;
are ignored.
/etc/modules-load.d/virtio-net.conf
# Load virtio-net.ko at boot virtio-net
See man 5 modules-load.d
for more details.
Configure module options
Additional module options must be set in the /etc/modprobe.d/modprobe.conf
.
Example:
- we have
/etc/modules-load.d/loop.conf
with moduleloop
inside to load during the boot.
- in the
/etc/modprobe.d/modprobe.conf
specify the additional options, e.g.options loop max_loop=64
Afterwards, the newly set option might be verified via cat /sys/module/loop/parameters/max_loop
Blacklisting
Module blacklisting works the same way as with initscripts since it is actually handled by kmod. See Module Blacklisting for details.
Filesystem mounts
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 /etc/fstab
should work out of the box.
See man 5 systemd.mount
for details.
Automount
- If you have a large
/home
partition, it might be better to allow services that do not depend on/home
to start while/home
is checked by fsck. This can be achieved by adding the following options to the/etc/fstab
entry of your/home
partition:
noauto,x-systemd.automount
This will fsck and mount /home
when it is first accessed, and the kernel will buffer all file access to /home
until it is ready.
Note: this will make your /home
filesystem type autofs
, which is ignored by mlocate by default. The speedup of automounting /home
may not be more than a second or two, depending on your system, so this trick may not be worth it.
- The same applies to remote filesystem mounts. If you want them to be mounted only upon access, you will need to use the
noauto,x-systemd.automount
parameters. In addition, you can use thex-systemd.device-timeout=#
option to specify a timeout in case the network resource is not available.
- If you have encrypted filesystems with keyfiles, you can also add the
noauto
parameter to the corresponding entries in/etc/crypttab
. Systemd will then not open the encrypted device on boot, but instead wait until it is actually accessed and then automatically open it with the specified keyfile before mounting it. This might save a few seconds on boot if you are using an encrypted RAID device for example, because systemd doesn't have to wait for the device to become available. For example:
/etc/crypttab
data /dev/md0 /root/key noauto
LVM
If you have LVM volumes not activated via the initramfs, enable the lvm-monitoring
service, which is provided by the lvm2 package:
# systemctl enable lvm-monitoring
Similarly, if you have LVM on encrypted devices mounted later during boot (e.g. from /etc/crypttab
), enable the lvm-on-crypt
service, which is also provided by the lvm2 package:
# systemctl enable lvm-on-crypt
ACPI power management
Systemd handles some power-related ACPI events. They can be configured via the following options from /etc/systemd/logind.conf
:
-
HandlePowerKey
: specifies which action is invoked when the power key is pressed. -
HandleSuspendKey
: specifies which action is invoked when the suspend key is pressed. -
HandleHibernateKey
: specifies which action is invoked when the hibernate key is pressed. -
HandleLidSwitch
: specifies which action is invoked when the lid is closed.
The specified action can be one of ignore
, poweroff
, reboot
, halt
, suspend
, hibernate
, hybrid-sleep
, lock
or kexec
.
If these options are not configured, systemd will use its defaults: HandlePowerKey=poweroff
, HandleSuspendKey=suspend
, HandleHibernateKey=hibernate
, and HandleLidSwitch=suspend
.
On systems which run no graphical setup or only a simple window manager like i3 or awesome, this may replace the acpid daemon which is usually used to react to these ACPI events.
systemctl restart systemd-logind.service
for your changes to take effect.In the current version of systemd, the Handle*
options will apply throughout the system unless they are "inhibited" (temporarily turned off) by a program, such as a power manager inside a desktop environment. If these inhibits are not taken, you can end up with a situation where systemd suspends your system, then when it wakes up the other power manager suspends it again.
Handle
options to ignore
if you want your ACPI events to be handled by Xfce, acpid or other programs.For systemctl hibernate
to work on your system you need to follow instructions at Hibernation and possibly at Mkinitcpio Resume Hook (pm-utils
does not need to be installed.)
Sleep hooks
Systemd does not use pm-utils to put the machine to sleep when using systemctl suspend
, systemctl hibernate
or systemctl hybrid-sleep
; pm-utils hooks, including any custom hooks, will not be run. However, systemd provides two similar mechanisms to run custom scripts on these events.
Suspend/resume service files
Service files can be hooked into suspend.target, hibernate.target and sleep.target to execute actions before or after suspend/hibernate. Separate files should be created for user actions and root/system actions. To activate the user service files, # systemctl enable suspend@<user> && systemctl enable resume@<user>
. Examples:
/etc/systemd/system/suspend@.service
[Unit] Description=User suspend actions Before=sleep.target [Service] User=%I Type=forking Environment=DISPLAY=:0 ExecStartPre= -/usr/bin/pkill -u %u unison ; /usr/local/bin/music.sh stop ; /usr/bin/mysql -e 'slave stop' ExecStart=/usr/bin/sflock [Install] WantedBy=sleep.target
/etc/systemd/system/resume@.service
[Unit] Description=User resume actions After=suspend.target [Service] User=%I Type=simple ExecStartPre=/usr/local/bin/ssh-connect.sh ExecStart=/usr/bin/mysql -e 'slave start' [Install] WantedBy=suspend.target
For root/system actions (activate with # systemctl enable root-suspend
):
/etc/systemd/system/root-resume.service
[Unit] Description=Local system resume actions After=suspend.target [Service] Type=simple ExecStart=/usr/bin/systemctl restart mnt-media.automount [Install] WantedBy=suspend.target
/etc/systemd/system/root-suspend.service
[Unit] Description=Local system suspend actions Before=sleep.target [Service] Type=simple ExecStart=-/usr/bin/pkill sshfs [Install] WantedBy=sleep.target
A couple of handy hints about these service files (more in man systemd.service
):
- If
Type=OneShot
then you can use multipleExecStart=
lines. Otherwise only one ExecStart line is allowed. You can add more commands with eitherExecStartPre
or by separating commands with a semicolon (see the first example above -- note the spaces before and after the semicolon...these are required!). - A command prefixed with '-' will cause a non-zero exit status to be ignored and treated as a successful command.
- The best place to find errors when troubleshooting these service files is of course with
journalctl
.
Combined Suspend/resume service file
With the combined suspend/resume service file, a single hook does all the work for different phases (sleep/resume) and for different targets (suspend/hibernate/hybrid-sleep).
Example and explanation:
/etc/systemd/system/wicd-sleep.service
[Unit] Description=Wicd sleep hook Before=sleep.target StopWhenUnneeded=yes [Service] Type=oneshot RemainAfterExit=yes ExecStart=-/usr/share/wicd/daemon/suspend.py ExecStop=-/usr/share/wicd/daemon/autoconnect.py [Install] WantedBy=sleep.target
-
RemainAfterExit=yes
: After started, the service is considered active until it is explicitly stopped. -
StopWhenUnneeded=yes
: When active, the service will be stopped if no other active service requires it. In this specific example, it will be stopped after sleep.target is stopped. - Because sleep.target is pulled in by suspend.target, hibernate.target and hybrid-sleep.target and sleep.target itself is a StopWhenUnneeded service, the hook is guaranteed to start/stop properly for different tasks.
Hooks in /usr/lib/systemd/system-sleep
Systemd runs all executables in /usr/lib/systemd/system-sleep/
, passing two arguments to each of them:
- Argument 1: either
pre
orpost
, depending on whether the machine is going to sleep or waking up - Argument 2:
suspend
,hibernate
orhybrid-sleep
, depending on which is being invoked
In contrast to pm-utils, systemd will run these scripts concurrently and not one after another.
The output of any custom script will be logged by systemd-suspend.service
, systemd-hibernate.service
or systemd-hybrid-sleep.service
. You can see its output in systemd's journal:
# journalctl -b -u systemd-suspend
Note that you can also use sleep.target
, suspend.target
, hibernate.target
or hybrid-sleep.target
to hook units into the sleep state logic instead of using custom scripts.
An example of a custom sleep script:
/usr/lib/systemd/system-sleep/example.sh
#!/bin/sh case $1/$2 in pre/*) echo "Going to $2..." ;; post/*) echo "Waking up from $2..." ;; esac
Don't forget to make your script executable:
# chmod a+x /usr/lib/systemd/system-sleep/example.sh
See man 7 systemd.special
and man 8 systemd-sleep
for more details.
Temporary files
Systemd-tmpfiles uses configuration files in /usr/lib/tmpfiles.d/
and /etc/tmpfiles.d/
to describe the creation, cleaning and removal of volatile and temporary files and directories which usually reside in directories such as /run
or /tmp
. Each configuration file is named in the style of /etc/tmpfiles.d/<program>.conf
. This will also override any files in /usr/lib/tmpfiles.d/
with the same name.
tmpfiles are usually provided together with service files to create directories which are expected to exist by certain daemons. For example the Samba daemon expects the directory /run/samba
to exist and to have the correct permissions. The corresponding tmpfile looks like this:
/usr/lib/tmpfiles.d/samba.conf
D /run/samba 0755 root root
tmpfiles may also be used to write values into certain files on boot. For example, if you use /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 man 5 tmpfiles.d
for details.
/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.Units
A unit configuration file encodes information about a service, a socket, a device, a mount point, an automount point, a swap file or partition, a start-up target, a file system path or a timer controlled and supervised by systemd. The syntax is inspired by XDG Desktop Entry Specification .desktop files, which are in turn inspired by Microsoft Windows .ini files.
See man 5 systemd.unit
for details.
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 1 systemctl
for more details.
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 the systemd-ui-gitAUR package from the AUR.Analyzing the system state
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). You can see list installed unit files by:
$ 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 shortforms when specifying the unit in the following systemctl
commands:
- If you don't specify the suffix, systemctl will assume
.service
. For example,netcfg
andnetcfg.service
are treated equivalent. - Mount points will automatically be translated into the appropriate
.mount
unit. For example, specifying/home
is equivalent tohome.mount
. - Similiar 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.
Activate a unit immediately:
# systemctl start <unit>
Deactivate 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>
[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.
# 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>
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.
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
Running DEs under systemd
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 and LightDM.
# systemctl enable kdm
This should work out of the box. If not, you might have a default.target
set manually or from a older install:
# ls -l /etc/systemd/system/default.target
/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
).
# rm /etc/systemd/system/default.target
Using systemd-logind
In order to check the status of your user session, you can use loginctl
. All PolicyKit actions like suspending the system or mounting external drives will work out of the box.
$ loginctl show-session $XDG_SESSION_ID
Writing custom .service files
See: Systemd/Services
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.
Type
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. See man systemd.service
for a more detailed explanation.
-
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 bylibsystemd-daemon.so
. -
Type=dbus
: The service is considered ready when the specifiedBusName
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 /etc/systemd/system/<unit>.d/
for example /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:
/etc/systemd/system/<unit>.d/customdependency.conf
[Unit] Requires=<new dependency> After=<new dependency>
Then run the following for your changes to take effect:
# systemctl daemon-reload # systemctl restart <unit>
Alternatively you can copy the old unit file from /usr/lib/systemd/system/
to /etc/systemd/system/
and make your changes there. A unit file in /etc/systemd/system/
always overrides the same unit in /usr/lib/systemd/system/
. Note that when the original unit in /usr/lib/
is changed due to a package upgrade, these changes will not automatically apply to your custom unit file in /etc/
. Additionally you will have to manually reenable the unit with systemctl reenable <unit>
. It is therefore recommended to use the *.conf
method described before instead.
systemd-delta
to see which unit files have been overridden and what exactly has been changed.Syntax highlighting for units within Vim
Syntax highlighting for systemd unit files within Vim can be enabled by installing vim-systemd from the official repositories.
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 runlevel
:
$ systemctl list-units --type=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 /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:
.target
extension can be left out.-
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 enable multi-user.target
The effect of this command is outputted by systemctl
; a symlink to the new default target is made at /etc/systemd/system/default.target
. This works if, and only if:
[Install] Alias=default.target
is in the target's configuration file. Currently, multi-user.target
and graphical.target
both have it.
Journal
Since version 38, systemd has its own logging system, the journal. Therefore, running a syslog daemon is no longer required. To read the log, use:
# journalctl
By default (when Storage=
is set to auto
in /etc/systemd/journald.conf
), the journal writes to /var/log/journal/
. The directory /var/log/journal/
is part of core/systemd. If you or some program delete it, systemd will not recreate it automatically, however it will be recreated during the next update of systemd. Till then, logs will be written to /run/systemd/journal
. This means that logs will be lost on reboot.
Filtering output
journalctl
allows you to filter the output by specific fields.
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). Currently, this feature is not implemented, though there was a discussion at systemd-devel@lists.freedesktop.org (September/October 2012).
As a workaround you can use at the moment:
# journalctl --since=today | tac | sed -n '/-- Reboot --/{n;:r;/-- Reboot --/q;p;n;b r}' | tac
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.
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
See man journalctl
, systemd.journal-fields
or Lennert'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 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 SystemMaxUse
in /etc/systemd/journald.conf
, so to limit it for example to 50 MiB uncomment and edit the corresponding line to:
SystemMaxUse=50M
Refer to man journald.conf
for more info.
Journald in conjunction with syslog
Compatibility with classic syslog implementations is provided via a socket /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 /dev/log
(official announcement). The syslog-ng package in the repositories automatically provides the necessary configuration.
# systemctl enable syslog-ng
A good journalctl
tutorial is here.
Optimization
Analyzing the boot process
Using systemd-analyze
Systemd provides a tool called systemd-analyze
that allows you to analyze your boot process so you can see which unit files are causing your boot process to slow down. You can then optimize your system accordingly.
To see how much time was spent in kernelspace and userspace on boot, simply use:
$ systemd-analyze
- If you append the
timestamp
hook to yourHOOKS
array in/etc/mkinitcpio.conf
and rebuild your initramfs withmkinitcpio -p linux
, systemd-analyze is also able to show you how much time was spent in the initramfs. - If you boot via UEFI and use a boot loader which implements systemds' Boot Loader Interface (which currently only Gummiboot does), systemd-analyze can additionally show you how much time was spent in the EFI firmware and the boot loader itself.
To list the started unit files, sorted by the time each of them took to start up:
$ systemd-analyze blame
You can also create a SVG file which describes your boot process graphically, similiar to Bootchart:
$ systemd-analyze plot > plot.svg
Using systemd-bootchart
Bootchart has been merged into systemd since Oct. 17, and you can use it to boot just as you would with the original bootchart. Add this to your kernel line:
initcall_debug printk.time=y init=/usr/lib/systemd/systemd-bootchart
Using bootchart2
You could also use a version of bootchart to visualize the boot sequence. Since you are not able to put a second init into the kernel command line you won't be able to use any of the standard bootchart setups. However the bootchart2AUR package from AUR comes with an undocumented systemd service. After you've installed bootchart2 do:
# systemctl enable bootchart
Read the bootchart documentation for further details on using this version of bootchart.
Readahead
Systemd comes with its own readahead implementation, this should in principle improve boot time. However, depending on your kernel version and the type of your hard drive, your mileage may vary (i.e. it might be slower). To enable, do:
# systemctl enable systemd-readahead-collect systemd-readahead-replay
Remember that in order for the readahead to work its magic, you should reboot a couple of times.
Troubleshooting
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 don't seem to log any output
If journalctl -u foounit.service
doesn't 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.
Diagnosing Boot Problems
Boot with these parameters on the kernel command line:
systemd.log_level=debug systemd.log_target=kmsg log_buf_len=1M
See also
- Official Web Site
- 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