Add tool to conver disk image into Docker image

dockerize-image tool takes a virtual disk image file
and creates a Docker image based on it. You can
specify a base Docker image to make this tool create
an image that will contain only filesystem diff
instead of full filesystem.
See tools usage for details.

Signed-off-by: Maxim Kulkin <maxim.kulkin@gmail.com>

contrib/dockerize-disk.sh

@@ -0,0 +1,118 @@
+#!/usr/bin/env bash
+set -e
+
+if ! command -v qemu-nbd &> /dev/null; then
+  echo >&2 'error: "qemu-nbd" not found!'
+  exit 1
+fi
+
+usage() {
+  echo "Convert disk image to docker image"
+  echo ""
+  echo "usage: $0 image-name disk-image-file [ base-image ]"
+  echo "   ie: $0 cirros:0.3.3 cirros-0.3.3-x86_64-disk.img"
+  echo "       $0 ubuntu:cloud ubuntu-14.04-server-cloudimg-amd64-disk1.img ubuntu:14.04"
+}
+
+if [ "$#" -lt 2 ]; then
+  usage
+  exit 1
+fi
+
+CURDIR=$(pwd)
+
+image_name="${1%:*}"
+image_tag="${1#*:}"
+if [ "$image_tag" == "$1" ]; then
+  image_tag="latest"
+fi
+
+disk_image_file="$2"
+docker_base_image="$3"
+
+block_device=/dev/nbd0
+
+builddir=$(mktemp -d)
+
+cleanup() {
+  umount "$builddir/disk_image" || true
+  umount "$builddir/workdir" || true
+  qemu-nbd -d $block_device &> /dev/null || true
+  rm -rf $builddir
+}
+trap cleanup EXIT
+
+# Mount disk image
+modprobe nbd max_part=63
+qemu-nbd -rc ${block_device} -P 1 "$disk_image_file"
+mkdir "$builddir/disk_image"
+mount -o ro ${block_device} "$builddir/disk_image"
+
+mkdir "$builddir/workdir"
+mkdir "$builddir/diff"
+
+base_image_mounts=""
+
+# Unpack base image
+if [ -n "$docker_base_image" ]; then
+  mkdir -p "$builddir/base"
+  docker pull "$docker_base_image"
+  docker save "$docker_base_image" | tar -xC "$builddir/base"
+
+  image_id=$(docker inspect -f "{{.Id}}" "$docker_base_image")
+  while [ -n "$image_id" ]; do
+    mkdir -p "$builddir/base/$image_id/layer"
+    tar -xf "$builddir/base/$image_id/layer.tar" -C "$builddir/base/$image_id/layer"
+
+    base_image_mounts="${base_image_mounts}:$builddir/base/$image_id/layer=ro+wh"
+    image_id=$(docker inspect -f "{{.Parent}}" "$image_id")
+  done
+fi
+
+# Mount work directory
+mount -t aufs -o "br=$builddir/diff=rw${base_image_mounts},dio,xino=/dev/shm/aufs.xino" none "$builddir/workdir"
+
+# Update files
+cd $builddir
+diff -rq disk_image workdir \
+  | sed -re "s|Only in workdir(.*?): |DEL \1/|g;s|Only in disk_image(.*?): |ADD \1/|g;s|Files disk_image/(.+) and workdir/(.+) differ|UPDATE /\1|g" \
+  | while read action entry; do
+      case "$action" in
+        ADD|UPDATE)
+          cp -a "disk_image$entry" "workdir$entry"
+          ;;
+        DEL)
+          rm -rf "workdir$entry"
+          ;;
+        *)
+          echo "Error: unknown diff line: $action $entry" >&2
+          ;;
+      esac
+    done
+
+# Pack new image
+new_image_id="$(for i in $(seq 1 32); do printf "%02x" $(($RANDOM % 256)); done)"
+mkdir -p $builddir/result/$new_image_id
+cd diff
+tar -cf $builddir/result/$new_image_id/layer.tar *
+echo "1.0" > $builddir/result/$new_image_id/VERSION
+cat > $builddir/result/$new_image_id/json <<-EOS
+{ "docker_version": "1.4.1"
+, "id": "$new_image_id"
+, "created": "$(date -u +%Y-%m-%dT%H:%M:%S.%NZ)"
+EOS
+
+if [ -n "$docker_base_image" ]; then
+  image_id=$(docker inspect -f "{{.Id}}" "$docker_base_image")
+  echo ", \"parent\": \"$image_id\"" >> $builddir/result/$new_image_id/json
+fi
+
+echo "}" >> $builddir/result/$new_image_id/json
+
+echo "{\"$image_name\":{\"$image_tag\":\"$new_image_id\"}}" > $builddir/result/repositories
+
+cd $builddir/result
+
+# mkdir -p $CURDIR/$image_name
+# cp -r * $CURDIR/$image_name
+tar -c * | docker load