[Solved] Problem booting root in LVM, which spans two LUKS partitions

Question

Hello,
I recently switched to Arch from OpenSuse, and I'm having a bit of trouble getting my encrypted disks to boot properly. I have two disks, the first is a 4 TB drive set up like this:
MBR partition table
Partition 1 - Windows 7, 200GB
Partition 2 - Linux boot, 200MB
Partition 3 - Luks partition, 1.7TB
Partition 4 - Luks partition, 1.7TB
Within partition 3 and 4 is an LVM volume which spans the two partitions. The reason for that is just that I can't have a 3.4TB partition on an MBR formatted drive (as I understand it). I have the root volume and swap, etc within this LVM. The second hard drive is simply a data drive, also encrypted. My problem is that I don't know how to tell the system to open both of these encrypted partitions at boot, in order to boot the root volume. This worked fine under OpenSuse and I only needed to enter the Luks password once (it is the same for both partitions).
As it is right now, my boot parameters in /etc/default/grub look like this:
GRUB_CMDLINE_LINUX_DEFAULT="quiet nomodeset cryptdevice=/dev/sda3:sda3_crypt root=/dev/mapper/vg_arch-root"
Currently the system boots, asks for the password to /dev/sda3, hangs for roughly 20 seconds and then kicks me into a root prompt. I can manually open /dev/sda4 at this point using cryptsetup and the system will continue booting normally... but I would like to have it set up properly, so I don't need to do that. Considering OpenSuse does this out of the box I figured it should be possible under Arch. Any help would be appreciated.
Thanks
Last edited by keitolainen (2015-06-09 21:56:08)

Answer 1

As a quick update in case anyone is reading this, I cleaned up the script a bit and hopefully made it something closer to a "proper" fix.
Rather than editing /usr/lib/initcpio/hooks/encrypt directly, I did the following:
cp /usr/lib/initcpio/hooks/encrypt /etc/initcpio/hooks/
then changed the following section of /etc/initcpio/hooks/encrypt from:
# Ask for a passphrase
if [ ${dopassphrase} -gt 0 ]; then
echo ""
echo "A password is required to access the ${cryptname} volume:"
#loop until we get a real password
while ! eval cryptsetup open --type luks ${resolved} ${cryptname} ${cryptargs} ${CSQUIET}; do
sleep 2;
done
fi
to:
# Ask for a passphrase
if [ ${dopassphrase} -gt 0 ]; then
echo ""
while true ; do
echo -n "A password is required to access the ${cryptname} volume: "
read -sr password
echo $password | cryptsetup open --type luks ${resolved} ${cryptname} ${cryptargs} ${CSQUIET}
if [ $? = 0 ] ; then
break
fi
done
echo $password | cryptsetup open --type luks /dev/sda4 sda4_crypt
echo ""
fi
then edited /etc/mkinitcpio.conf and changed:
FILES=""
to:
FILES="/etc/initcpio/hooks/encrypt"
and ran
mkinitcpio
This is working well for me and I think it's a little cleaner than the solution I posted earlier. Sorry for the awkward bash, if anyone has a more elegant solution please let me know.