Ubuntu – Can’t run fsck in recovery mode in >18.04. Disk is mounted r/w

You will have to use the desktop cd (iso). You would boot the live iso with your VM, and run fsck from a terminal.

The server CD, as you can see, has a very limited "live" environment, and is used primarily for installation.

To check the LVM it is done with the following steps.

First we can see our drive layout with lsblk:

# lsblk
NAME                 MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                    8:0    0    20G  0 disk  
└─sda1                 8:1    0    20G  0 part  
  └─xubuntu--vg-root 253:0    0    19G  0 lvm   / 
sr0                   11:0    1  1024M  0 rom   

as we can see the LVM is named xubuntu--vg-root, but we cannot run fsck on this name as it will not find it. We need to get the whole name. To do this we are going to run the lvm lvscan command to get the LV name so we can run fsck on the LVM.

The following commands should be ran as sudo or as a root user.

# lvscan
  inactive          '/dev/xubuntu-vg/root' [<19.04 GiB] inherit
  inactive          '/dev/xubuntu-vg/swap_1' [980.00 MiB] inherit

As we can see our name to check is /dev/xubuntu-vg/root so we should be able to run fsck on that name

If the /dev/xubuntu-vg/root is not ACTIVE, we need to make it active so that we can run the check on it

lvchange -ay /dev/xubuntu-vg/root

Now it should look like this:

# lvscan
  ACTIVE            '/dev/xubuntu-vg/root' [<19.04 GiB] inherit
  inactive          '/dev/xubuntu-vg/swap_1' [980.00 MiB] inherit

Now we can run the fsck on the LVM volume.

fsck /dev/xubuntu-vg/root

or to run a forced check with assume yes

fsck -fy /dev/xubuntu-vg/root

Adding a screen shot since VirtualBox will not let me copy and paste.

Hope this helps!