systemd is a system and service manager. systemctl is a main command of systemd


$ journalctl
list all running services, sockets, etc. (units).

Change Runlevel

# systemctl isolate   analog to runlevel5 of SysV
# systemctl isolate   ... level3
# systemctl isolate   ... level1

Reboot and Power Off

# systemctl soft-reboot

soft-reboot restarts user space components without touching the Linux kernel. The acceleration of the reboot is achieved by excluding relatively long stages such as hardware initialization, bootloader operation, kernel startup, driver initialization, firmware loading, and initrd processing [techplanet].

systemd-soft-reboot.service -

$ systemctl reboot

$ systemctl poweroff

Change Display Manager

# systemctl disable gdm
# systemctl enable xdm

List of Processes

$ systemd-cgls
$ ps xawf -eo pid,user,cgroup,args
tree view of processes belonging to services and logged-in user.

List of Units

$ tree /etc/systemd/   currently used units
$ tree /lib/systemd/   all available units

3 Levels of OFF

# systemctl stop
terminates the running unit.

# systemctl disable
prevents activation of unit on boot, by socket or bus (or by other triggers) activation. Howerver, the unit can be started manually.

# systemct mask
# ln -s /dev/null /etc/systemd/system/example.service
# systemctl daemon-reload
disable unit completely (can not be started anymore).

Analyze Boot-Up Performance

journalctl --since=today | grep userspace
show the boot-up time (the time spent in the kernel before userspace has been reached).

systemd-analyze blame
print a list of all running units, ordered by the time they took to initialize.


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