I have a linux mint 18 installation with a luks encrypted / and swap partitions. / which is /dev/sda6 unlocks and mounts fine at boot up. The system then goes into emergency mode. journalctl says timeout trying to reach the swap partition.

I tried running cryptsetup open --type luks /dev/sda5 sda5_cryptand that returns Device /dev/sda5 is not a valid LUKS device.

  • 2
    If the swap partition got zotted by a dirty shutdown, you might just have to destroy the swap partition entirely - including the encrypted container - and recreate it.
    – DopeGhoti
    Apr 17, 2017 at 22:31

1 Answer 1


DopeGhoti is correct.

To confirm a corrupted LUKS header, you can use the following command:

cryptsetup luksDump /dev/sda5

You should get the same error message.

To fix it, re-create the LUKS container, setup the swap again, and take a backup of the LUKS header. Something like this:

cryptsetup luksFormat /dev/sda5
cryptsetup open --type luks /dev/sda5 sda5_crypt
mkswap -L SWAP /dev/mapper/sda5_crypt
swapon -L SWAP
cryptsetup luksHeaderBackup /dev/sda5 --header-backup-file /root/sda5_luks_header.img

The LUKS header is so vulnerable. There's only one copy so when you lose it, there's no way to unlock the device. Unless... you have a backup ;)

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