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| /{{ year }}/{{ month }}/{{ day }}/problems-after-disconnecting-luks-device | Problems after disconnecting LUKS device | 2013-01-14 23:28:00 +0100 | post.liquid |
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Yesterday I got my 2TB backup disk. I formatted it and then used LUKS to encrypt it and LVM for the Volume Management. After I copied some files to the new disk, I unmounted the disk, unplugged it and ...
... Oh, shit.
I forgot to cryptsetup luksClose it.
That's not a good thing to do. Always remember to luksClose! It's so much easier
So after reconnecting the device, you can't really decrypt and mount it, because it did not get unmapped (/dev/mapper/name still exists and so do /dev/name/*)
No problem, we fix that!
(in the following my mapping name is extern, change accordingly)
First see current status, especially Open count
dmsetup info
Now remove each mapped device (-backup and -media for me, I have 2 partiions on the disk):
dmsetup remove extern-backup
dmsetup remove extern-media
Once again check Open count, it should be 0 now. If so, go on and remove the mapping:
dmsetup remove extern
Now you got rid of all old mappings. Let's try to mount the disk again. Plug it in, then do:
cryptsetup luksOpen /dev/sdb2 extern
Type your password. If the Volume Groups are missing, use:
vgscan
vgchange -ay extern
Now you can mount your partitions:
mount /dev/extern/backup /mnt/backup
Once you're done, deactivate the volume groups and close the crypt device:
vgchange -an extern
cryptsetup luksClose extern
Now remember to always use these two commands after unmounting the device and use the following to open it:
vgchange -ay extern
cryptsetup luksOpen /dev/sdb2 extern
I wrote a little helper script which does exactly these steps as needed. I'll include it in my next post, when I talk about how I use the setup for backups.