Linux Run Level

The Linux system runs at a specified runlevel, with different running levels of programs and services that are different for different purposes.
0: All processes will terminate and the machine will be in shutdown state
1: Single-user mode for system maintenance, enabling a small number of processes, all services not running.
2: Multi-user mode, and Level 3, just NFS (Network File System) service does not start.
3: Multi-user mode, allowing multiple users to log on to the system, is the default boot level of the system.
4: Custom Run level.
5: Multi-user mode, run graphical interface.
6: All processes are terminated and the system restarts.

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Run and view the current run level
#runlevel
User switch Run level
#init "0-6"
If the character interface, switch the graphical interface
#startx

Linux Run Level