Recover root password or failed mount

Overview

If you need to set the root password on a Centos 7 instance or fix a faulty /etc/fstab for example, then this is the procedure to access the boot disk without a root password.

Modify boot parameters

1. Reboot the instance and press “e” when the grub 2 boot menu is shown.

2. Add the following parameters at the end of the linux16 line:

   rd.break enforcing=0

3. Remove all parameters starting with “console=”

4. Press Ctrl+x to boot

Set password

1. Remount the root filesystem read write.

$ mount -o remount,rw /sysroot

2. You can now edit the root disk files under /sysroot.

3. To set a new password do a change root and set password.

$ chroot /sysroot
$ passwd

4. Exit both shells and the instance will reboot.

$ exit