Booting into read-only file system

Solution 1:

I had the same problem when booting into a copied root filesystem (I forgot to adjust UUID values in /etc/fstab). It turns out mount -o remount still looks in /etc/fstab if you don't specify a device. It worked when manually specifying a device:

mount -o remount,rw /dev/sda1 /

Solution 2:

Now lets try this fix:

1. Boot into recovery mode
2. Select root from recovery menu.

3. Mount file system with:

   mount -o remount,rw /
   

4. Using vim or nano change your /etc/fstab like so:

   #UUID=/dev/sda1 /               ext4    errors=remount-ro 0       1
   UUID=643d9cab-177e-4eee-a52f-224ebf0bc405 /               ext4    errors=remount-ro 0       1
   

5. Then exit and select resume from recovery menu, that should fix your issue.

Solution 3:

There is something wrong in your /etc/fstab.

UUID=/dev/sda1 /               ext4    errors=remount-ro 0       1
# UUID=643d9cab-177e-4eee-a52f-224ebf0bc405 /               ext4    errors=remount-ro 0 

THe first line is wrong, /dev/sda1 isn't a uuid. The second line looks like the correct one. Put a # in front of the first line, and remove it on the line below.

You can verify the UUID by blkid /dev/sda1 .. if it differs, change the one in /etc/fstab so that it matches.

OR you can remove the UUID= in front of /dev/sda1