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

#!/bin/bash

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

# Create 1 partition far enough up the disk to permit grub to be installed on
# the MBR.
sudo sfdisk $IMAGE_BLOCK_DEVICE << EOF
1 - - *
0 0;
0 0;
0 0;
EOF

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
fi

if [ -n "$DM" ]; then
    echo "IMAGE_BLOCK_DEVICE=${DM}p1"
else
    echo "IMAGE_BLOCK_DEVICE=${IMAGE_BLOCK_DEVICE}p1"
fi