Comment 1 for bug 120375

Sorry folks, being tooo fast.

This is not working if all discs are present, now i understand the include of MD_DEGRADED_ARGS

my new workaround is to add a bootmenue entry in grub

title Ubuntu, kernel 2.6.20-16-generic (raid defect)
root (hd0,1)
kernel /boot/vmlinuz-2.6.20-16-generic root=/dev/md1 ro raid_degraded
initrd /boot/initrd.img-2.6.20-16-generic

and /etc/initramfs-tools/scripts/init-premount/raid_degraded

#!/bin/sh

set -eu

PREREQ="udev"

prereqs()
{
        echo "$PREREQ"
}

case ${1:-} in
  prereqs)
    prereqs
    exit 0
    ;;
  *)
    . /scripts/functions
    ;;
esac

if [ -e /scripts/local-top/md ]; then
  log_warning_msg "old md initialisation script found, getting out of its way..."
  exit 1
fi

MDADM=$(command -v mdadm)
[ -x $MDADM ] || exit 0

if grep raid_degraded /proc/cmdline 2>/dev/null; then
  echo "MD_DEGRADED_ARGS=' '" >> /conf/md.conf
fi

exit 0

now if a disc is defect and i will to start only with one disc i choose raid defect from bootmenu