Linux-Basics-Complete-Course-With-Notes-Slides

Run Levels

Systemd Targets (Run Levels)

We can setup the server to boot either into graphical mode or non-graphical mode. Linux can run in multiple modes and these modes are set by something called runlevel

• The operation mode which provide a graphical interface is called runlevel 5

• The operation mode which provide a non-graphical mode is called runlevel 3

  

To see the operation mode run in the system. Run the command runlevel from the terminal

$ runlevel

During boot, the init process checks the runlevel, it make sure that all programs need to get the system operation in that mode are started.

• For example: The Graphical User mode requires a display manager service to run for the GUI to work, however this service is not required for the non-graphical mode

  

In the boot process section, we saw that the systemd is used as the init process in most new linux distributions suchs as Ubuntu 18.04.

• In systemd, runlevels are called as targets.
  • The RunLevel 5 is called as the graphical target

  • The Runlevel 3 is called as the multiuser target

    

Now that we are familiar with runlevels in systemd target unit. Lets now take a look at how we change these values from a shell.

To see the default target, run the command systemctl get-default. This command looks at the file located at /etc/systemd/system/default.target

$ systemctl get-default

To change the default target, we can make use of systemctl set-target <desired target name goes here as an argument>

$ systemctl set-default multi-user.target