Runlevel description:

• 0: turn it off
• 1: single user [retrieve lost password]
• 2: no network service is available in the multi-user state
• 3: The network service is available in the multi-user state
• 4: The system is not in use
• 5: Graphical interface
• 6: The system restarts

Common runlevels are 3 and 5, but you can also specify a default runlevel.

• Prior to centos7, the configuration run level was in/etc/inittabIn the file
• Centos7 has been simplified as follows:

multi-user.target: analogous to runlevel 3
graphical.target: analogous to runlevel 5
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• Explanation:

multi-user.target is equivalent to init3The level graphical. Target is equivalent to init5levelCopy the code

• To view current default target (view current run level), run (run) :

systemctl get-default
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• To set a default target, run:

systemctl set-default TARGET.target
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• Switching to a graphical interface (Init 5 runlevel) :

systemctl set-default graphical.target
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• After restarting the system based on the above runlevel switch, it will still enter the terminal interface of Init 3, and will not enter the graphical interface again