Booting into Rescue Mode in CentOS

This post will go over booting into rescue mode in CentOS.  To be able to boot into rescue mode, you will need to boot to the install media and select "Rescue installed system".

You will then need to pick a language, keyboard, and whether or not you want networking enabled.  Depending on the situation, you can then try to mount the system as read-write, read-only, or skip mounting the system.

Assuming the system has started successfully and the filesystems have been mounted successfully, you are now in runlevel 1, you now have a temporary root filesystem at /, and the actual system filesystems exist under /mnt.

You can then chroot to the filesystem to be able to execute commands as if you had booted to the actual os.  This will allow you to troubleshoot the system without the need for a full boot.

If all you need is root access to the local filesystem, you can boot into runlevel 1 from the grub boot screen by appending the word "single" at the end of the kernel line.