[dm-crypt] configuration files

Jonas Meurer jonas at freesources.org
Sat Feb 20 09:55:39 CET 2010


hey sven,

On 17/02/2010 Selim Levy wrote:
> The cause:
> During the CD installation of debian, the debian installer associates the
> external hard drive to /dev/sdb.  However, following the installation, when
> I boot *from* the external hard drive, the system associates it with
> /dev/sda.  So essentially, I'm installing linux (and dm-crypt and everything
> else) to /dev/sdb, though it will then be called /dev/sda when I boot from
> it.
> 
> The question:
> I've already made the necessary changes to GRUB and the /boot partition is
> booting properly -- I can get a busybox prompt -- but I'm unable to continue
> booting into the root partition.  Where are the files on /boot located that
> must be changed in order for the boot partition to properly deal with the
> dm-crypt encrypted LVM volume group?  I have already found the
> conf/conf.d/cryptroot file within my initrd image and have modified both
> lines in it.  (One line is for the root partition, the other for swap.)
> I've modified the 'target=' and the 'source=' entries (on both llines) to
> show 'sda3' as opposed to the original 'sdb3'.  What else must be changed?

you need to change both /etc/crypttab and /etc/fstab on the rescue
system, and maybe even /etc/initramfs-tools/conf.d/resume.
afterwards you'll have to regenerate the initramfs image. the best way
to do so is to:
- unlock and mount the rootfs of your rescue system to /mnt/rescue
- copy /proc/modules, /proc/cmdline and /proc/devices to
  /mnt/rescue/proc
- bind-mount /dev to /mnt/rescue/dev: 'mount -o bind /dev /mnt/rescue/dev'
- chroot into /mnt/rescue/dev
- modify /proc/cmdline, /etc/crypttab and /etc/fstab
- run 'update-initramfs -u'

this is written down from memory, i hope that i didn't forget anything.

greetings,
 jonas
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