diskimage-builder/elements/ubuntu-core/root.d/10-cache-ubuntu-image

#!/bin/bash
# These are useful, or at worst not harmful, for all images we build.

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

[ -n "$ARCH" ]
[ -n "$TARGET_ROOT" ]

shopt -s extglob

DIB_CLOUD_IMAGES=${DIB_CLOUD_IMAGES:-http://cdimage.ubuntu.com/ubuntu-core/preview}
DIB_RELEASE=${DIB_RELEASE:-alpha-01}
BASE_IMAGE_FILE=${BASE_IMAGE_FILE:-ubuntu-core-$DIB_RELEASE.img}
BASE_IMAGE_TAR=$DIB_RELEASE-ubuntu-core.tgz
SHA256SUMS=${SHA256SUMS:-$DIB_CLOUD_IMAGES/SHA256SUMS}
CACHED_FILE=$DIB_IMAGE_CACHE/$BASE_IMAGE_FILE
CACHED_TAR=$DIB_IMAGE_CACHE/$BASE_IMAGE_TAR
CACHED_SUMS=$DIB_IMAGE_CACHE/SHA256SUMS.ubuntu-core.$DIB_RELEASE

if [ -n "$DIB_OFFLINE" -a -f "$CACHED_TAR" ] ; then
    echo "Not checking freshness of cached $CACHED_TAR"
else
    echo "Fetching Base Image"
    $TMP_HOOKS_PATH/bin/cache-url $SHA256SUMS $CACHED_SUMS
    $TMP_HOOKS_PATH/bin/cache-url $DIB_CLOUD_IMAGES/$BASE_IMAGE_FILE $CACHED_FILE

    pushd $DIB_IMAGE_CACHE
    if ! grep "$BASE_IMAGE_FILE" $CACHED_SUMS | sha256sum --check - ; then
        # It is likely that an upstream http(s) proxy has given us a skewed
        # result - either a cached SHA file or a cached image. Use cache-busting
        # to get (as long as caches are compliant...) fresh files.
        # Try the sha256sum first, just in case that is the stale one (avoiding
        # downloading the larger image), and then if the sums still fail retry
        # the image.
        $TMP_HOOKS_PATH/bin/cache-url -f $SHA256SUMS $CACHED_SUMS
        if ! grep "$BASE_IMAGE_FILE" $CACHED_SUMS | sha256sum --check - ; then
            $TMP_HOOKS_PATH/bin/cache-url -f \
                $DIB_CLOUD_IMAGES/$BASE_IMAGE_FILE $CACHED_FILE
            grep "$BASE_IMAGE_FILE" $CACHED_SUMS | sha256sum --check -
        fi
    fi
    popd

    if [ ! -f $CACHED_TAR -o \
        $DIB_IMAGE_CACHE/$BASE_IMAGE_FILE -nt $CACHED_TAR ] ; then

        echo "Repacking base image as tarball."
        WORKING=$(mktemp -d)
        EACTION="rm -r $WORKING"
        trap "$EACTION" EXIT
        RAW_FILE=$(basename $BASE_IMAGE_FILE)
        RAW_FILE=${RAW_FILE%.img}.raw
        qemu-img convert -f qcow2 -O raw $CACHED_FILE $WORKING/$RAW_FILE
        MAGIC_BIT=p1
        # NOTE: On RHEL, partprobe of /dev/loop0 does not create /dev/loop0p2,
        # while kpartx at least creates /dev/mapper/loop0p2.
        LOOPDEV=$(sudo kpartx -av $WORKING/$RAW_FILE | awk "/loop[0-9]+$MAGIC_BIT/ {print \$3}")
        # If running inside Docker, make our nodes manually, because udev will not be working.
        if [ -f /.dockerenv ]; then
            sudo dmsetup --noudevsync mknodes
        fi
        export LOOPDEV=$LOOPDEV
        echo "Loop device is set to: $LOOPDEV"
        if ! timeout 5 sh -c "while ! [ -e /dev/mapper/$LOOPDEV ]; do sleep 1; done"; then
            echo "Error: Could not find /dev/mapper/$LOOPDEV"
            exit 1
        fi
        EACTION="sudo kpartx -d $WORKING/$RAW_FILE;$EACTION"
        trap "$EACTION" EXIT
        mkdir $WORKING/mnt
        sudo mount /dev/mapper/$LOOPDEV $WORKING/mnt
        EACTION="sudo umount -f $WORKING/mnt;$EACTION"
        trap "$EACTION" EXIT
        # Chroot in so that we get the correct uid/gid
        sudo chroot $WORKING/mnt bin/tar -cz . > $WORKING/tmp.tar
        mv $WORKING/tmp.tar $DIB_IMAGE_CACHE/$BASE_IMAGE_TAR
    fi
fi

# Extract the base image (use --numeric-owner to avoid UID/GID mismatch between
# image tarball and host OS e.g. when building Ubuntu image on an openSUSE host)
sudo tar -C $TARGET_ROOT --numeric-owner -xzf $DIB_IMAGE_CACHE/$BASE_IMAGE_TAR