# Selectively disable growroot               -*- shell-script -*-
set -e
PREREQ=""
prereqs()
{
  echo "$PREREQ"
}

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

message() { echo "DISABLE-GROWROOT:" "$@" ; }
error_exit() { message "$@"; exit 1; }

. /scripts/functions

# initramfs-tools exports the following variables, used below:
# $ROOT - Generally "/dev/disk/by-uuid/<id>" which is a link to /dev/sda1
# $ROOTFLAGS - Generally empty
# $ROOTFSTYPE - Generally empty
# $rootmnt - Set to "/root"

# According to the initramfs documentation, it's supposed to wait until
# the disks have been attached and verified before the local-premount scripts
# run. This does not happen, however, and failures can happen below if $ROOT
# is referenced before the disk that it points to is attached. This allows for
# up to 4 seconds for that to happen. In practice, it generally takes less
# than half a second.
for i in $(seq 1 20); do
  if [ -e "${ROOT}" ]; then
    break
  fi
  sleep 0.2
done

# Follow link to get real root location
if [ ! -L "${ROOT}" ]; then
  real_root=${ROOT}
else
  real_root=$(readlink -f "${ROOT}")
fi

# Remove partition number to get disk
disk=$(echo ${real_root} | sed 's/[0-9]*$//')

# Determine number of 512-byte sectors in 2TB
two_tb=$((2*(1024**4)))
max_sectors=$((${two_tb}/512))

# Determine number of sectors on disk
geometry=$(sfdisk ${disk} --show-pt-geometry)
cyl=$(echo $geometry | cut -d " " -f 2)
heads=$(echo $geometry | cut -d " " -f 4)
secs=$(echo $geometry | cut -d " " -f 6)
sectors=$((${cyl}*${heads}*${secs}))

# If disk is >2TB, disable growroot
if [ "$sectors" -gt "$max_sectors" ]; then
  message "Disk size >2TB - Not expanding root partition"
  # Temporarily mount filesystem
  if [ -z "${ROOTFSTYPE}" ]; then
    fstype=$(get_fstype "${ROOT}")
  else
    fstype=${ROOTFSTYPE}
  fi
  mount -w ${fstype:+-t ${fstype} }${ROOTFLAGS} ${ROOT} ${rootmnt} ||
      error_exit "failed to mount ${ROOT}."
  # Disable growroot
  touch "${rootmnt}/etc/growroot-disabled"
  # Unmount filesystem
  umount "${rootmnt}" || error_exit "failed to umount ${rootmnt}";
fi