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.
