Switch Between CLI and GUI

How to change between the cmdline interface and the GUI by editing the boot target.

First, we no longer use the runlevel term. Instead, we refer to boot choices as targets. The 2 primary targets here: multi-user.target (the CLI or runlevel 3 in legacy) and the graphical.target (the GUI or runlevel 5 in legacy).

To identify the current target:

$ sudo systemctl get-defeault

To launch GUI from the multi-user.target:

$ sudo systemctl isolate graphical.target

And to switch back to CLI mode:

$ sudo systemctl usolate multi-user.target

To set a default target

$ sudo systemctl  set-default multi-user.target

To reboot and confirm the appropriate target:

$ sudo systemctl reboot

Target Files

Targets are managed by .target files that simply group units and dependencies into a convenient format. It;s really the .unit files that define exactly what services and other features start when the target is initiated.

$ sudo systemctl enable sshd

$ sudo systemctl disable sshd

 

Links:

• Linux Run Levels
  

Linux Run Levels

Linux changes the run-level:

• (Old Linux distro) SysV init uses run-level number from 0 to 6.
• cmdline: init, telinit, who
  
• (New Linux distro) systemd init uses systemd targets.
• cmdline: systemctl 

 

Linux runlevel defines the state of the OS. 

SysV	Systemd targets	Description
0	runlevel0.target poweroff.target	Halt or shutdown the Linux system
1	runlevel1.target rescue.target	Single-user text mode (useful for maintenance mode)
2	runlevel2.target multi-user.target	Not used
3	runlevel3.target multi-user.target	Full multi-user text mode (used on Linux servers)
4	runlevel4.target multi-user.target	Not used
5	runlevel5.target graphical.target	Full multi-user GUI mode. You can use X-based login screen. Useful for Linux desktop
6	runlevel6.target reboot.target	Reboot Linux system

Comparing the cmdline used.

SysV	Systemd	Description
runelvel who -r	systemctl get-default	Show the current runlevel
init 1	systemctl rescue systemctl emergency	Change the runlevel to single user mode for maintenance
init 3	systemctl multi-user-target	Change to multi-user text mode
init 0	systemctl poweroff	Poweroff
init 6	systemctl reboot	Reboot
	systemctl default	Back to default target
init 5	systemctl graphical.target	Change to GUI mode

Links:

• https://www.cyberciti.biz/tips/linux-changing-run-levels.html