Redhat7:systemd targets

Previously and Now..

In the old versions of Redhat services that used the SysV or upstart, implemented in a predifined set of run levels that each represented a specific mode of operation. The run levels were numbered from 0-6.

Runlevels have now been replaced with the concept of systemd targets. Each target is represented by a target unit, which end with the .target file extension.

Targets units only purpose is to group together other systemd units, using dependencies. As an example the graphical.target unit is used to start a graphical session, starts the GNOME display Manager (gdm-service).

Redhat7 has a number of predefined targets which are more or less equivalent to the runlevels of RHEL6. To make life easier there a aliases set up to reflect this.

Comparison of SysV runlevels with systemd targets
Run Level	Target Units	Description
0	runlevel0.target poweroff.target	Shutdown the system and power off the system
1	runlevel1.target rescue.target	Set up a resuce shell
2	runlevel2.target multi-user.target	Set up a non-graphical multi-user system
3	runlevel3.target multi-user.target	Set up a non-graphical multi-user system
4	runlevel4.target multi-user.target	Set up a non-graphical multi-user system
5	runlevel5.target graphical.target	Set up a graphical multi-user system
6	runlevel6.target reboot.target	Shut down and reboot the system