Systemd has replaced sysVinit as the default service manager in RHEL 7. Some of the sysVinit commands have been symlinked to their RHEL 7 counterparts, however this will eventually be deprecated in favor of the standard systemd commands in the future.
SysVinit V/s systemd runlevels
Here is a comparison between SysVinit runlevels V/s systemd targets.
| Sysvinit Runlevel | Systemd Target | Function |
|---|---|---|
| 0 | runlevel0.target, poweroff.target | System halt/shutdown |
| 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 mode, text console only |
| 5 | runlevel5.target, graphical.target | Multi-user, graphical mode |
| 6 | runlevel6.target, reboot.target | Reboot |
| emergency | emergency.target | Emergency mode |
Changing runlevels with systemd
The runlevel target can be changed by using the systemctl isolate command :
# systemctl isolate multi-user.target
To view what targets are available you can issue the list-units option with the type target
# systemctl list-units --type=target
Run level 3 is emulated by multi-user.target. This is done by symbolic link and can be used interchangeably
# systemctl isolate multi-user.target # systemctl isolate runlevel3.target # ls -l /usr/lib/systemd/system/runlevel3.target lrwxrwxrwx 1 root root 17 Oct 18 11:41 /usr/lib/systemd/system/runlevel3.target -> multi-user.target
Run level 5 is emulated by graphical.target. This is also done by symbolic link and can be used interchangeably
# systemctl isolate graphical.target # systemctl isolate runlevel5.target # ls -l /usr/lib/systemd/system/runlevel5.target lrwxrwxrwx 1 root root 16 Oct 18 11:41 /usr/lib/systemd/system/runlevel5.target -> graphical.target
Changing the default runlevel
The default runlevel can be changed by using the set-default option.
# systemctl set-default multi-user.target
To get the currently set default, you can use the get-default option.
# systemctl get-default
The default runlevel in systemd can also be set using the below method (not recommended though).
# ln -sf /lib/systemd/system/[desired].target /etc/systemd/system/default.target
The default target can also be set in the kernel line during boot by adding the following option :
systemd.unit=multi-user.target