Run Levels / Operating Modes

Linux has 7 different run levels (or operating modes):

  • 0 - System Halted
  • 1 - Single User Mode
  • 2 - Single User Mode with Networking
  • 3 - Multi-User Mode - boot up in text mode
  • 4 - Not yet Defined
  • 5 - Multi-User Mode - boot up in X Windows
  • 6 - Shutdown & Reboot

chkconfig is used to list all the registered services and display thier status at each different run level.

The runlevel command:

runlevel prints the previous and current SysV runlevel if they are known. The two runlevel characters are separated by a single space character. If a runlevel cannot be determined, N is printed instead. If neither can be determined, the word "unknown" is printed. Unless overridden in the environment, this will check the utmp database for recent runlevel changes. This is a legacy command available for compatibility only. It should not be used anymore, as the concept of runlevels is obsolete.

See also systemd(1), systemctl(1)

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