[dm-crypt] cryptsetup luksClose

Milan Broz mbroz at redhat.com
Tue Jan 17 09:50:56 CET 2012

On 01/16/2012 03:48 PM, Marc Schwarzschild wrote:
> I am setting up an external USB encrypted drive. I can mount it
> manually after I boot the computer. I understand that I must
> issue the 'cryptsetup luksClose' after I umount the disk. How do
> I arrange for this as part of the Debian halt process so it
> happens automatically when the server is shutdown?

It is not cryptsetup job, it should be part of initscripts/systemd
to correctly unmap active devices on shutdown.
(Usually it tries to unmap all crypto disks except device
with root fs which is just remounted read-only. Recent systemd is able
to unmouteven root device properly.)

For hot-plugged disks it is usually handled by some GUI service,
usually based on udisks.

> What happens
> if there is a power failure and 'cryptsetup luksClose' was not
> executed?

For LUKS, no need to worry after power failure - luksClose
just remove kernel mapping (kernel state) it doesn't touch
on-disk metadata at all.
(Of course there can be some filesystem damage after power failure,
but that's not LUKS related, it can happen even for unencrypted fs.)


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