Runlevels in System V

  • Runlevel 0: Halt
  • Runlevel 1: Single user mode
  • Runlevel 6: Reboot

All System V init scripts are stored in /etc/rc.d/init.d/ or /etc/init.d directory. These scripts are used to control system startup and shutdown. Usually you will find scripts to start a web server or networking. For example you type the command:
# /etc/init.d/httpd start
# /etc/init.d/network restart