Re: [dm-crypt] configuration files

[Jonas Meurer <jonas@freesources.org>]

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hey selim,

On 21/02/2010 Selim Levy wrote:
> On 21 February 2010 12:10, Bryan Kadzban <bryan.kadzban@gmail.com> wrote:
> > Doesn't Debian's initramfs bring up udev and let you use the
> > /dev/disk/by-*/ symlinks in crypttab?  That's a *LOT* better way to find
> > this drive (in your case, by-id might work, and by-uuid will almost
> > definitely work, assuming a new-enough udev that can find the UUID of a
> > LUKS volume).  Maybe poke around in /dev/disk when you're at the busybox
> > prompt, and see what you can find.
> > (If it doesn't bring up udev and let you use those symlinks, then ...
> > why not?  :-P  Not a question for you obviously, but more for the Debian
> > maintainers.)
> >
> > Anyway, then you don't care which sd* name is given to this device,
> > since you're using an explicitly-guaranteed-stable name for it.
> >
> 
> Hmmmm.... that's really interesting.  I played around at the busybox prompt
> and took down all the info in the /dev/disk/by-* directories (which do get
> created).  I redirected output of 'ls -alF' commands from those directories
> to file and have the info available to me.
> 
> So here's what I've now confirmed:
> When I boot into my main/internal hd, /dev/sda, sdb and sdc are the
> following: internal hd, cardreader, external hd (respectively).
> When I boot into my rescue/external system, they are the following: internal
> hd, external hd, cardreader.
> 
> How do I go about using the /dev/disk/by-* devices with dm-crypt?  Does it
> only require modifying, as before, /etc/fstab and /proc/cmdline?  Or is
> there something else I should play around with?

yon can use "UUID=..." instead of the device path both in /etc/fstab and
in /etc/crypttab. for example:

/etc/fstab:
UUID=9385bada-5c09-a303-ee31-4fd23452af29 / ext3 errors=remount-ro 0 1

/etc/crypttab:
sdb3_crypt UUID=35bc3457-127a-4344-80bf-6cdfff232339 none luks

/proc/cmdline:
BOOT_IMAGE=/vmlinuz-2.6.26-1-amd64 root=/dev/mapper/rescue-rooto ro

you need to substitute the UUID in /etc/fstab with the UUID of
/dev/mapper/rescue-rooto, and the UUID in /etc/crypttab with the one of
/dev/sdb3.

greetings,
 jonas

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