fsck Dirty Bit Reported

Question

MY COMPUTER

-Model: Msi GL72 7QF -Processor: Intel i7-7700HQ; 2.8GH -RAM: 16GB DDR4 -GPU: nVidia GTX960M, Optimus enabled -SSD: 500GB, GPT UEFI -OS: Windows10 Insider Preview; Mageia 7; Ubuntu 18.04.3 LTS

Secure boot and fast boot are disabled.

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I'm trying to install Ubuntu 18.04.3 and am receiving an error message that Grub cannot install. One of the things I did to troubleshoot was run fsck to examine the ESP partition. This is the results:

root@msi:~# fsck /dev/sda2
fsck from util-linux 2.31.1
fsck.fat 4.1 (2017-01-24)
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
1) Remove dirty bit
2) No action
? 2
There are differences between boot sector and its backup.
This is mostly harmless. Differences: (offset:original/backup)
  65:01/00
1) Copy original to backup
2) Copy backup to original
3) No action
? 3
/dev/sda2: 725 files, 16131/76646 clusters
root@msi:~# 

I chose not to fix anything because I don't know what fsck is telling me. What is a dirty bit and why should I care about it? Also, since I'm having trouble installing Ubuntu, do I really want to rely on the backup boot sector? Any insights would be greatly appreciated.

Solution

It would mean that at some time during shutdown of your computer, your EFI partition, which is a vfat file system, was not properly unmounted. The linux kernel sets the dirty bit when mounting and clears it when unmounting.

For now, fix the error by unmounting the device and issuing the command fsck -a /dev/sda2. This would repair the volume using default assumptions.

Comments

[Yogi]

Thank you for the hint. That cleared the dirty bit, but I am still getting the error when trying to install Ubuntu/Grub.

[Michael Levy]

I also get a dirty bit when I try FSCK from the safe mode. When I try your suggestion in the command line, I read "WARNING!!! The filesystem is mounted. If you continue you WILL cause SEVERE filesystem damage." What can I do? Thoughts?

[vanadium]

The warning speaks for itself. You may not check a file system that is currently in use.