Linux 4: Run Levels

0 — System halt
1 — Single User
2 — Multiple Users No NFS (No Network File System)
3 — Multiple Users Command Line
4 — User definable
5 — Multiple Users GUI
6 — Multiple Users Reboot

Single User Mode

• Boots multi user system into single super user
• Mainly used for maintenance
• Some tasks may require exclusive access to shared resources
• Can also be used for security purposes
• Network services not running
• On some systems lost superuser passwords can be reset by switching into superuser mode

Edit GRUB to go single

• Select menu entry to edit
• Press e
• Go to Kernel line
• Press e(??)
• Type single at the end of the line
• Press Esc
• Press b to boot