Repairing fstab (read only /)

That was very easy to correct fstab from readonly mode. We must mount / in read-write mode.

If /etc/fstab is correct, you can simply type:

mount -n -o remount /

But if /etc/fstab is wrong (as it was in my case), you must give the device name and possibly the type, too: e.g.

mount -n -o remount -t extX /dev/hdaX /

Where extX is your filesystem type and /dev/hdaX -- is partition you use for your root mount point.

mount -n -o remount -t ext4 /dev/sda1 /