Emergency Mode & Filesystem Repairing

Emergency Mode

Emergency mode is similar to single-user mode except the root filesystem is mounted read-only and runlevel 1 is not used. Boot into emergency mode using the same method as single-user mode except replace the word single with emergency in the boot method.

Because the filesystem is mounted read-only, files can not be changed or repaired, but files can be retrieved off the system.

Filesystem Repair

If one or more filesystem are corrupt, boot into rescue mode and do not mount the filesystem. Even if you can boot into single-user mode, do not use it because the filesystem cannot be repaired if it is mounted.

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Single-User Mode

Single-user mode is equivalent to runlevel 1 on the system. If runlevel 1 is not configured properly, you will not be able to boot into single-user mode. Rescue mode requires a boot media, but single-user mode is specified as a kernel option using the installed boot loader and does not require additional boot media. However, it does require that the boot loader is working properly and that the filesystem be mounted. It does not provide the ability to start a network connection.

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Recovery and Repair Linux system

To analyze or repair a system failure, you might need to boot into the system. But, what if the boot loader is corrupt or what if the filesystem can’t be mounted anymore? Red Hat Enterprise Linux includes alternative boot methods for system repair: rescue mode, single user mode, and emergency mode.

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