= Moving the root filesystem to an LVM volume in etch =

== What is the problem? ==

I experienced quite some trouble when migrating etch to an LVM volume. Thus I documented the process below.

Afterwards I found this [[http://linux.derkeiler.com/Mailing-Lists/Debian/2006-08/msg01699.html|posting]], which claims, that it should not be a problem at all, if you start it correctly. Please read that post and try if it works for you, before you continue reading.

== Details of migration ==
 * split the active raid 1 mirror: {{{
mdadm --fail /dev/md2 /dev/hdb5
mdadm --remove /dev/md2 /dev/hdb5
}}}
 * create a new raid 1 mirror: {{{
mdadm --create /dev/md3 --raid-devices=2 --raid-level=mirror /dev/hdb5 missing
}}}
 * create an LVM physical volume, a volume group and the logical volume: {{{
pvcreate /dev/md3
vgcreate base-lvm /dev/md3
lvcreate -n root -L 5G base-lvm
mkfs.ext3 /dev/base-lvm/root
}}}
 * copy the old system to the new volume: {{{
mount /dev/base-lvm/root /mnt
cp -axv / /mnt/
}}}
 * backup the current initrd file and the ''menu.lst'': {{{
cp /boot/initrd-XXX /boot/initrd-XXX_before_lvm
cp /boot/grub/menu.lst /boot/grub/menu.lst_before_lvm
}}}
 * chroot into the new system on lvm: {{{
mount --bind /dev /mnt/dev
mount --bind /boot /mnt/boot
chroot /mnt
mount /proc
mount /sys
}}}
 * change the root filesystem in ''/etc/fstab'': {{{
/dev/base-lvm/root      /               ext3    noatime,errors=remount-ro 0       1
}}}
 * copy the following script to ''/usr/share/initramfs-tools/hooks/lvm'': {{{
#!/bin/sh

PREREQ=""

prereqs()
{
        echo "$PREREQ"
}

case $1 in
prereqs)
        prereqs
        exit 0
        ;;
esac

if [ ! -x /sbin/lvm ]; then
        exit 0
fi

. /usr/share/initramfs-tools/hook-functions

if [ -e /etc/lvm/lvm.conf ]; then
        mkdir -p ${DESTDIR}/etc/lvm
        cp /etc/lvm/lvm.conf ${DESTDIR}/etc/lvm/
fi

copy_exec /sbin/lvm /sbin
# this is the self-made stuff to get it running under etch ...
cp -a /sbin/lv* $DESTDIR/sbin
cp -a /sbin/vg* $DESTDIR/sbin
cp -a /sbin/pv* $DESTDIR/sbin
cp -a /lib/lvm-200 $DESTDIR/lib
cp -a /lib/lvm-default $DESTDIR/lib
# also copy the required libraries
ldd /lib/lvm-200/lvm | cut -f 1 -d " " | cut -f 2 | sed s#^l#/lib/l# | while read fname
  do    test -e $DESTDIR$fname || cp "$fname" $DESTDIR$fname
 done

for x in dm_mod dm_snapshot dm_mirror; do
        manual_add_modules ${x}
done
}}}
  * the script is heavily based
 * run {{{update-initramfs -u}}}
 * change the root device for grub:
  * update the placeholder in ''/boot/grub/menu.lst'': {{{
# kopt=root=/dev/mapper/base--lvm-root ro
}}}
   * BEWARE: in ''etch'' you '''must''' use the ''/dev/mapper/XXXX'' location (instead of the ''/dev/vg/lv''-style)
  * update the grub menu file: {{{
update-grub
}}}
 * reboot
 * hope for mercy :)