Systemd vs Init Cheatsheet for Linux

Last Updated : 28 Mar, 2022

Systemd is the new init framework, beginning with Fedora and presently embraced in numerous circulations like RedHat, Suse, and Centos. All things considered, the vast majority of us have been utilizing conventional SysV init scripts typically living in/and so on/rc.d/init.d/. These contents conjure a daemon parallel which will then, at that point, fork a foundation cycle. Despite the fact that shell scripts are entirely adaptable, undertakings like administering processes and parallelized execution requesting are challenging to carry out. With the presentation of systemd's recent fad daemons, it is more straightforward to oversee and control them at runtime and it works on their execution.

The systemctl order is an awesome drive by the systemd group. It shows more point-by-point blunder messages and furthermore runtime mistakes of administrations including fire up blunders. systemd has presented another term called cgroups (control gatherings) which is essentially gatherings of interaction that can be sorted out in order. With the first init framework, figuring out which cycle does what and who it has a place with turns out to be progressively troublesome. With systemd, when cycles generate different cycles these kids are naturally made individuals from the guardians cgroup subsequently staying away from disarrays about legacy.

Service-Related Commands :

Comments	SysVinit	Systemd
Start a service	service dummy start	systemctl start dummy.service
Stop a service	service dummy stop	systemctl stop dummy.service
Restart a service	service dummy restart	systemctl restart dummy.service
Reload a service	service dummy reload	systemctl reload dummy.service
Service status	service dummy status	systemctl status dummy.service
Restart a service if already running	service dummy condrestart	systemctl condrestart dummy.service
Enable service at startup	chkconfig dummy on	systemctl enable dummy.service
Disable service at startup	chkconfig dummy off	systemctl disable dummy.service
Check if a service is enabled at startup	chkconfig dummy	systemctl is-enabled dummy.service
Create a new service file or modify configuration	chkconfig dummy --add	systemctl daemon-reload

Runlevels commands:

Comments	SysVinit	Systemd
System halt	0	runlevel0.target, poweroff.target
Single user mode	1, s, single	runlevel1.target, rescue.target
Multi user	2	runlevel2.target, multi-user.target
Multi user with Network	3	runlevel3.target, multi-user.target
Experimental	4	runlevel4.target, multi-user.target
Multi user, with network, graphical mode	5	runlevel5.target, graphical.target
Reboot	6	runlevel6.target, reboot.target
Emergency Shell	emergency	emergency.target
Change to multi user runlevel/target	telinit 3	systemctl isolate multi-user.target (OR systemctl isolate runlevel3. target)
Set multi-user target on next boot	sed s/^id:.*:initdefault:/ id:3:initdefault:/	ln -sf /lib/systemd/system/multiuser.target /etc/systemd/system/ default.target
Check current runlevel	runlevel	systemctl get-default
Change default runlevel	sed s/^id:.*:initdefault:/ id:3:initdefault:/	systemctl set-default multi-user.target

Systemd New Commands :

Comments	Systemd
Execute a systemd command on remote host	systemctl dummy.service start -H user@host
Check boot time	systemd-analyze or systemd-analyze time
Kill all processes related to a service	systemctl kill dummy
Get logs for events for today	journalctl --since=today
Hostname and other host related information	hostnamectl
Date and time of system with timezone and other information	timedatectl