Use the dracut shell to troubleshoot filesystems

I have a test VM running Fedora 18 with btrfs filesystems. After applying the latest OS updates the machine failed to boot failing over to a dracut shell. Here’s a short guide on what I did to recover it.

First some OS info:

During the boot process these messages were displayed after switching back and forth from text mode to GUI mode by pressing the ESC key:

Eventually I got a dracut shell where I typed help and got access to a bunch of utilities:

With the help of dmesg I found what went wrong:

It was one of the btrfs partitions that was causing the issues. Just to be sure I searched and found all btrfs partitions that were automatically mounted and ran the btrfsck tool to fix the errors:

dmesg | less
mount
umount /dev/sda2 /dev/sdb1
btrfsck /dev/sda2
btrfsck /dev/sdb1

After fixing the errors I hit CTRL+D to exit the dracut shell and the OS booted successfully.

 

More info on:

• btrfs
• dracut shell

 

Hope this helps.