Add tar as an output type

Add support for d-i-b to create tarballs, the primary consumer for
tarball images would be linux containers.

Change-Id: I27d67401f3e4415226a4a51e1dde46f739c0220a

README.md

@@ -23,7 +23,9 @@ What tools are there?
   Element dependencies are automatically included. Support for other
   architectures depends on your environment being able to run binaries of that 
   platform. For instance, to enable armhf on Ubuntu install the qemu-user-static
-  package.
+  package. The default output format from disk-image-create is qcow2. To instead
+  output a tarball pass in "-t tar". This tarball could then be used as an image
+  for a linux container(see docs/docker.md).
 
 * ramdisk-image-create -o filename {element} [{element} ...] : Create a kernel+
   ramdisk pair for running maintenance on bare metal machines (deployment,

bin/disk-image-create

@@ -46,6 +46,7 @@ function show_options () {
     echo "Options:"
     echo "    -a i386|amd64|armhf -- set the architecture of the image(default amd64)"
     echo "    -o imagename -- set the imagename of the output image file(default image)"
+    echo "    -t qcow2|tar -- set the imagetype of the output image file(default qcow2)"
     echo "    -x -- turn on tracing"
     echo "    -u -- uncompressed; do not compress the image - larger but faster"
     echo "    -c -- clear environment before starting work"
@@ -83,7 +84,7 @@ function show_options () {
 
 INSTALL_PACKAGES=""
 COMPRESS_IMAGE="true"
-TEMP=`getopt -o a:ho:xucnp: -l no-tmpfs,offline,help,min-tmpfs:,image-size:,image-cache:,max-online-resize: -n $SCRIPTNAME -- "$@"`
+TEMP=`getopt -o a:ho:t:xucnp: -l no-tmpfs,offline,help,min-tmpfs:,image-size:,image-cache:,max-online-resize: -n $SCRIPTNAME -- "$@"`
 if [ $? -ne 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi
 
 # Note the quotes around `$TEMP': they are essential!
@@ -93,6 +94,7 @@ while true ; do
     case "$1" in
         -a) export ARCH=$2; shift 2 ;;
         -o) export IMAGE_NAME=$2; shift 2 ;;
+        -t) export IMAGE_TYPE=$2; shift 2 ;;
         -h|--help) show_options; exit 0;;
         -x) shift; set -x;;
         -u) shift; export COMPRESS_IMAGE="";;
@@ -181,9 +183,15 @@ mount_proc_dev_sys
 run_d_in_target finalise
 finalise_base
 
+if [ "$IMAGE_TYPE" == "tar" ]; then
+  sudo tar -C ${TMP_BUILD_DIR}/mnt -cf $IMAGE_NAME.tar --exclude ./sys \
+           --exclude ./proc --xattrs --xattrs-include=\* .
+  sudo chown $USER: $IMAGE_NAME.tar
+fi
+
 unmount_image
 
-if [ "$IS_RAMDISK" == "0" ]; then
+if [ "$IS_RAMDISK" == "0" -a "$IMAGE_TYPE" != "tar" ]; then
   compress_and_save_image $IMAGE_NAME.$IMAGE_TYPE
 else
   # This is a ramdisk build, we have already extracted the kernel and ramdisk

docs/docker.md

@@ -0,0 +1,18 @@
+Creating Docker Images
+======================
+
+disk-image-create can be used to create a tarball suitable to be imported as a
+docker image. To do this you can change the output of disk-image-create to tar
+with the -t flag and run docker e.g.
+
+```
+disk-image-create -o image -t tar fedora selinux-permissive
+```
+
+Assuming you have docker running and have permission to use it, the tarball can
+be imported into docker and run.
+
+```
+docker import - image:test1 < image.tar
+docker  run -t -i  image:test1 /bin/bash
+```