diskimage-builder/elements/vm/block-device.d/10-partition

#!/bin/bash

if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
    set -x
fi
set -eu
set -o pipefail

source $_LIB/die
[ -n "$IMAGE_BLOCK_DEVICE" ] || die "Image block device not set"

# Create 2 partitions for PPC, one for PReP boot and other for root
if [[ "$ARCH" =~ "ppc" ]] ; then
    sudo sfdisk --force $IMAGE_BLOCK_DEVICE << EOF
0,8,41 *
,,L
;
EOF
else
    # sfdisk changed around 2.26 and was largely rewritten.  The old
    # version defaults to c/h/s and interprets arguments as cylinders.
    # The new version defaults to sectors.
    #
    # Luckily, the old version has a -uS flag (ignored by the new
    # version) to interpret arguments as sectors.  However, it
    # incorrectly calculates the c/h/s offset when finding free space,
    # and gets upset [1], requiring the use of --force.
    #
    # TODO: switch this to parted, or something saner (is there such a
    # thing when talking about partitioning?)
    #
    # The below command creates a partition that starts at 1MiB --
    # which is the standard place to start a partition these days --
    # and fills up the disk.  The zeros are to ignore the other 3
    # primary partitions (probably not needed, but left for safety).
    #
    # [1] https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1481158
    sudo sfdisk -uS --force $IMAGE_BLOCK_DEVICE << EOF
2048 + L *
0 0;
0 0;
0 0;
EOF
fi

sudo partprobe $IMAGE_BLOCK_DEVICE

# To ensure no race conditions exist from calling partprobe
sudo udevadm settle

# If the partition isn't under /dev/loop*p1, create it with kpartx
DM=
if [ ! -e "${IMAGE_BLOCK_DEVICE}p1" ]; then
    DM=${IMAGE_BLOCK_DEVICE/#\/dev/\/dev\/mapper}
    # If running inside Docker, make our nodes manually, because udev will not be working.
    if [ -f /.dockerenv ]; then
        # kpartx cannot run in sync mode in docker.
        sudo kpartx -av $TMP_IMAGE_PATH
        sudo dmsetup --noudevsync mknodes
    else
        sudo kpartx -asv $TMP_IMAGE_PATH
    fi
elif [[ "$ARCH" =~ "ppc" ]]; then
    sudo kpartx -asv $TMP_IMAGE_PATH
fi

if [ -n "$DM" ]; then
    echo "IMAGE_BLOCK_DEVICE=${DM}p1"
elif [[ "$ARCH" =~ "ppc" ]]; then
    DM=${IMAGE_BLOCK_DEVICE/#\/dev/\/dev\/mapper}
    echo "IMAGE_BLOCK_DEVICE=${DM}p2"
else
    echo "IMAGE_BLOCK_DEVICE=${IMAGE_BLOCK_DEVICE}p1"
fi