SysVinit to Systemd Cheatsheet

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This is a document to help system administrators who need to understand what commands in systemd replace their old workflow in SysVinit.  If you want generation information on systemd, refer to [[systemd]]  
 
This is a document to help system administrators who need to understand what commands in systemd replace their old workflow in SysVinit.  If you want generation information on systemd, refer to [[systemd]]  
  

Revision as of 22:46, 12 April 2011

This is a document to help system administrators who need to understand what commands in systemd replace their old workflow in SysVinit. If you want generation information on systemd, refer to systemd

Note that the 'service' and 'chkconfig' commands will continue to work as expected in the systemd world, this guide is how to use the native systemctl calls that are being made by those commands.

Services

SystemVinit Command Systemd Command Notes
ls /etc/rc.d/init.d/ ls /lib/systemd/system/*.service /etc/systemd/system/*.service Used to list the services that can be started or stopped
chkconfig frobozz systemctl is-enabled frobozz.service; echo $? Used to check whether a service is configured to start or not in the current environment.
chkconfig frobozz --list ls /etc/systemd/system/*.wants/frobozz.service Used to list what levels this service is configured on or off
chkconfig frobozz --add systemctl enable frobozz.service Set a service to run in the runlevels specified in the init script[nb 1]
chkconfig frobozz --level 12345 on for target in rescue multi-user ; do ln -s /lib/systemd/system/frobozz.service /etc/systemd/system/$target.target.wants/ && systemctl daemon-reload Turn the service on for the next reboot. [nb 2]
chkconfig frobozz --level 12345 off for target in rescue multi-user ; do rm /etc/systemd/system/$target.target.wants/frobozz.service && systemctl daemon-reload Turn the service off for the next reboot. [nb 2]
service frobozz start systemctl start frobozz.service (OR service frobozz start) Used to start a service (not reboot persistent)
service frobozz stop systemctl stop frobozz.service (OR service frobozz stop) Used to stop a service (not reboot persistent)
service frobozz restart systemctl restart frobozz.service (OR service frobozz restart) Used to stop and then start a service
service frobozz reload systemctl reload frobozz.service (OR service frobozz reload) When supported, reloads the config file without interrupting pending operations.
service frobozz condrestart systemctl reload-or-restart frobozz.service (OR systemctl condrestart frobozz.service OR service frobozz condrestart) When supported, restarts if the service is already running.
service frobozz status systemctl status frobozz.service Tells whether a service is currently running.
Warning (medium size).png
Additional commands
In SysVinit, services can define arbitrary commands. Examples would be service iptables panic, or service httpd graceful. Native systemd services do not have this ability.

Any service that defines an additional command in this way would need to define some other, service-specific, way to accomplish this task when writing a native systemd service definition.

Check the package-specific release notes for any services that may have done this.

Notes

  1. Although chkconfig --add and systemctl enable perform roughly the same action, chkconfig --add is recommended when you first install a service while systemctl enable is recommended when you first turn a service on.
  2. 2.0 2.1 In systemd, the numeric runlevels have been replaced by named targets. The graphical target is a strict superset of the multi-user target so you don't have to set it up separately. The custom runlevels (2 and 4 in this example) are not defined well enough to have a real systemd equivalent; if you use them for custom runlevels, you should try a custom named target in systemd instead. See the Runlevels section for more details

Runlevels/targets

Systemd has a concept of 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. 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. 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's 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/$YOURTARGET that takes one of the existing runlevels as a base (you can look at /lib/systemd/system/graphical.target as an example), make a directory /etc/systemd/system/$YOURTARGET.wants, and then symlink the additional services that you want to enable into that directory. (The service unit files that you symlink live in /lib/systemd/system).

SystemVinit 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

Changing runlevels:

SystemVinit Command Systemd Command Notes
telinit 3 systemctl isolate multi-user.target (OR systemctl isolate runlevel3.target OR telinit 3) Change to multi-user run level.
sed s/^id:.*:initdefault:/id:3:initdefault:/ ln -sf /lib/systemd/system/multi-user.target /etc/systemd/system/default.target Set to use multi-user runlevel on next reboot.