• Spawned from the kernel
• init creates all processes
• Has process ID 1
• Runs processes in /etc/inittab

Run Levels

• Software configuration
• A selection of processes running concurrently
• Usually set by:
• kernel parameter
• initdefault setting in /etc/inittab
• running telinit

Predefined run levels

• 0 - Halt
• 1 - Single user mode
• 2 - Multiuser, without NFS
• 3 - Full multiuser mode
• 4 - unused
• 5 - X11
• 6 - reboot