Книга: Fedora™ Unleashed, 2008 edition

Runlevel Definitions

Runlevel Definitions

The Fedora runlevels are defined for the Fedora system in /etc/inittab.

Each runlevel tells the init command what services to start or stop. Although runlevels might all have custom definitions, Fedora has adopted some standards for runlevels:

? Runlevel 0 — Known as "halt," this runlevel is used to shut down the system.

? Runlevel 1 — This is a special runlevel, defined as "single," which boots Fedora to a root access shell prompt where only the root user may log in. Networking, X, and multiuser access are turned off. This is the maintenance or rescue mode. It allows the system administrator to perform work on the system, make backups, or repair configuration or other files.

? Runlevel 2 — This runlevel dictates that Fedora be booted to a console, or text-based mode, with multiuser access.

? Runlevel 3 — This runlevel is identical to runlevel 2, except that it also starts any networking services.

? Runlevel 4 — This runlevel is undefined, and it can readily be configured to boot Fedora to a custom system state.

? Runlevel 5 — This runlevel boots Fedora to a networking, multiuser state with an active X session. This is the most common runlevel for home users who want a graphical interface.

? Runlevel 6 — This runlevel is used to reboot the system.

Runlevel 1 (also known as single-user mode or maintenance mode) is most commonly used to repair file systems and change the root password on a system when the password has been forgotten. Trespassers with physical access to the machine can also use runlevel 1 to access your system.

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