fsck e2fsck: Cannot continue, aborting [duplicate]

When I tried to run fsck on Ubuntu 18.04 recovery-mode I got the following message. Can anyone tell me why?

/lib/recocery-mode/recovery-menu: line 80: /etc/default/rcS: No such file or directory
fsck from util-linux 2.31.1
/dev/sda4 is mounted
e2fsck: Cannot continue, aborting.

Solution 1:

The error is telling you that you cannot use e2fsck while the target file system is mounted. You must unmount the file system first using umount /dev/sda4. If you're currently booted into a system that has that volume mounted it's likely that you cannot unmount it. You should probably use a USB stick and run e2fsck from that.

Solution 2:

You don't say what command you're using, so do it this way...

To check the file system on your Ubuntu partition...

• boot to the GRUB menu
• choose Advanced Options
• choose Recovery mode
• choose Root access
• at the # prompt, type sudo fsck -f /
• repeat the fsck command if there were errors
• type reboot

If for some reason you can't do the above...

• boot to a Ubuntu Live DVD/USB
• start gparted and determine which /dev/sdaX is your Ubuntu EXT4 partition
• quit gparted
• open a terminal window
• type sudo fsck -f /dev/sda4 # replacing 4 with the number you found earlier
• repeat the fsck command if there were errors
• type reboot