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My Ubuntu 11.04 machine uses LUKS encryption for root, swap and home. A routine fsck -n revealed a set of errors I need to repair. fsck requires to unmount the partitions. Before luks I would simply boot from a USB stick and fix run fsck from there. What are the steps to do that for LUKS encrypted partitions?

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up vote 13 down vote accepted

The exact method depends on how you have setup luks, and if you have LVM on top of luks or if you just have a filesystem within the luks volume.

If you don't have LVM in addition to luks then you would probably do something like this.

cryptsetup luksOpen /dev/rawdevice somename
fsck /dev/mapper/somename

# or

cryptsetup luksOpen /dev/sda2 _dev_sda2
fsck /dev/mapper/_dev_sda2

If you used the LVM on LUKS option providied by the Debian/Ubuntu installer, then you'll need to start up LVM. So vgchange -aly after opening the encrypted volume, then run fsck against the /dev/mapper/lvname.

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For whatever reason cryptsetup luksOpen /dev/rawdevice somename wasn't working out to give me something to run fsck on, although it was showing up with vgscan just fine after vgchange -ay as 'active'... I had to create the raw devices manually with vgscan --mknodes and then fsck on the logical volume showing up in vgscan with fsck /dev/cryptVG/root - Hope this helps someone else out there – Dmitri DB Nov 2 '14 at 18:30
Hm, no matter if I use cryptsetup or cryptdisk_start, I get the same result when I try fsck: /dev/mapper/ext_crypt is in use. I checked mount and it is not mounted anywhere. – Nikodemus May 14 at 8:27

You need to open the LUKS volume first.

cryptsetup luksOpen /dev/(whatever) someName

This'll ask you for the password, then create /dev/mapper/someName, which is the plaintext device that you can run fsck on. When you're done,

cryptsetup luksClose someName

will remove the /dev/mapper/someName plaintext device, .

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