There are 7 runlevels at linux. these are:
runlevel 0 --> shutdown
runlevel 1--> single user
runlevel 2--> multiuser without NFS
runlevel 3--> multiuser with NFS
runlevel 4--> not in use
runlevel 5 --> Graphical user interface
runlevel 6 --> restart
We can go to any runlevel by typing init runlevel . As for example to go to graphical user mode we can type init 5. To restart we can type init 6, to shutdown init 0 etc.
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