Run levels in linux shell

A Linux system can be in specific run level. Linux system usually can have 7 run level (0-6).
  • 0 run level is used to shut down the system.
  • 6 run level is used to reboot the system.
Run levels 1 to 5 are used to start the system in single user or multi user mode and with or without networking. We can use below command to check run level of the system.
 
$ runlevel
$ who -r

To know which processes will start in any of the run level, you can use below command.
 
$ chkconfig

You can use below command to shut down the system.
 
$ init 0

You can use below command to restart the system.
 
$ init 6

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