Activates a service immediately:
systemctl start foo.service
Deactivates a service immediately:
systemctl stop foo.service
Restarts a service:
systemctl restart foo.service
Shows status of a service including whether it is running or not:
systemctl status foo.service
Enables a service to be started on bootup:
systemctl enable foo.service
Disables a service to not start during bootup:
systemctl disable foo.service
Check whether a service is already enabled or not:
0 indicates that it is enabled. 1 indicates that it is disabled
systemctl is-enabled foo.service; echo $?
Change ad-hoc runlevel with systemctl isolate command:
Switch to another target (in this case multi-user/runlevel 3 in old SysV):
systemctl isolate multi-user.target
Switch to graphical target (in this case graphical/runlevel 5 in old SysV):
systemctl isolate graphical.target
Change permanently change default.target:
Remove configured default target
rm /etc/systemd/system/default.target
Create default.target as symbolic link to multi-user.target
ln -sf /lib/systemd/system/multi-user.target /etc/systemd/system/default.target
Set default target through systemctl ``` To find a [new target]:
systemctl set-default [new target]
List-units by pattern:
```shell
systemctl list-units *etwok*.service
Example content:
UNIT LOAD ACTIVE SUB DESCRIPTION
network.service loaded active exited LSB: Bring up/down networking
NetworkManager.service loaded active running Network Manager
LOAD = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB = The low-level unit activation state, values depend on unit type.
2 loaded units listed. Pass --all to see loaded but inactive units, too.
Display a content of unit file
systemctl cat network.service
Displayed content:
# /run/systemd/generator.late/network.service
# Automatically generated by systemd-sysv-generator
[Unit]
Documentation=man:systemd-sysv-generator(8)
SourcePath=/etc/rc.d/init.d/network
Description=LSB: Bring up/down networking
Before=runlevel2.target runlevel3.target runlevel4.target runlevel5.target shutdown.target network-online.target network.target
After=iptables.service ip6tables.service NetworkManager-wait-online.service NetworkManager.service
Wants=network-online.target
Conflicts=shutdown.target
[Service]
Type=forking
Restart=no
TimeoutSec=5min
IgnoreSIGPIPE=no
KillMode=process
GuessMainPID=no
RemainAfterExit=yes
ExecStart=/etc/rc.d/init.d/network start
ExecStop=/etc/rc.d/init.d/network stop
ExecReload=/etc/rc.d/init.d/network reload
Suppress non zero exit code (service after stop will be displayed as inactive, not failed):
[Service]
SuccessExitStatus=143
Link:
- [services-remain-in-failed-state-after-stopped-with-systemctl] (https://serverfault.com/questions/695849/services-remain-in-failed-state-after-stopped-with-systemctl)
How to put PID of service as variable to service systemd file:
ExecReload=/bin/kill -s HUP $MAINPID
Link
List all services with pattern
<pattern> - httpd e.g
systemctl list-units -t service --full | grep <pattern> | sed 's/^\s*//g' | cut -d " " -f1 | while read s; do systemctl status $s; done
Link
List all enable units
systemctl list-unit-files | grep enabled
smartd.service enabled
sshd.service enabled
sysstat.service enabled
...
Link
Reference links:
Pid Eins:
Digital Ocean: