SystemD commands cheatsheet

Systemd is the new system and service manager for Linux. It is a replacement for init system and can manage system startup and services. It starts up and supervises the entire system.

List all running services

# systemctl

Start/stop or enable/disable services

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:

# systemctl is-enabled foo.service; echo $?

0 indicates that it is enabled. 1 indicates that it is disabled

 

How do I change the runlevel?

systemd has the concept of targets which is a more flexible replacement for runlevels in sysvinit.

Run level 3 is emulated by multi-user.target. Run level 5 is emulated by graphical.target. runlevel3.target is a symbolic link to multi-user.target and runlevel5.target is a symbolic link to graphical.target.

You can switch to ‘runlevel 3′ by running

# systemctl isolate multi-user.target (or) systemctl isolate runlevel3.target

You can switch to ‘runlevel 5′ by running

# systemctl isolate graphical.target (or) systemctl isolate runlevel5.target

 

How do I change the default runlevel?

systemd uses symlinks to point to the default runlevel. You have to delete the existing symlink first before creating a new one.

# rm /etc/systemd/system/default.target

Switch to runlevel 3 by default

# ln -sf /lib/systemd/system/multi-user.target /etc/systemd/system/default.target

Switch to runlevel 5 by default

# ln -sf /lib/systemd/system/graphical.target /etc/systemd/system/default.target

systemd does not use /etc/inittab file.

 

List the current run level

runlevel command still works with systemd. You can continue using that however runlevels is a legacy concept in systemd and is emulated via ‘targets’ and multiple targets can be active at the same time. So the equivalent in systemd terms is

# systemctl list-units --type=target

 

Powering off the machine

You can use

# poweroff

Some more possibilities are: halt -p, init 0, shutdown -P now

Note that halt used to work the same as poweroff in previous Fedora releases, but systemd distinguishes between the two, so halt without parameters now does exactly what it says – it merely stops the system without turning it off.

 

Service vs. systemd

# service NetworkManager stop

(or)

# systemctl stop NetworkManager.service

 

Chkconfig vs. systemd

# chkconfig NetworkManager off

(or)

# systemctl disable NetworkManager.service

 

Readahead

systemd has a built-in readahead implementation. It should improve bootup speed but your mileage may vary depending on your hardware. To enable it:

# systemctl enable systemd-readahead-collect.service
# systemctl enable systemd-readahead-replay.service

 

List the services that can be started or stopped

ls /lib/systemd/system/*.service /etc/systemd/system/*.service

 

Check whether a service is configured to start or not in the current environment

 systemctl is-enabled foobar.service

 

List what levels this service is configured on or off

ls /etc/systemd/system/*.wants/foobar.service

 

To reload the configuration of service (say ssh), without restarting it

systemctl reload sshd