Move initial root contents into a hook.

This is a necessary but not complete step towards supporting Fedora and Suse
distributions. Further work is needed (e.g. to quiesce daemons on
installation).

Change-Id: If3ea6093d41a21de755db52328226b84b5a3ede6

.gitignore

@@ -5,3 +5,4 @@
 .tox
 *.egg-info
 dist
+*.qcow2

README.md

@@ -87,6 +87,16 @@ Writing an element
 Make as many of the following subdirectories as you need, depending on what
 part of the process you need to customise:
 
+* root.d: Create or adapt the initial root filesystem content. This is where
+  alternative distribution support is added, or customisations such as
+  building on an existing image. If no element configures a root, the ubuntu
+  element will be automatically invoked to obtain an Ubuntu image.
+  Runs outside the chroot on the host environment, so should cleanup after
+  itself using the root-finished.d hook.
+  NB: Only one element can use this at a time.
+
+ * inputs: $ARCH=i386|amd64 $TARGET\_ROOT=/path/to/target/workarea
+
 * block-device-size.d: Alter the size (in GB) of the disk image. This is useful
   when a particular element will require a certain minimum (or maximum) size.
   You can either error and stop the build, or adjust the size to match.
@@ -94,8 +104,8 @@ part of the process you need to customise:
   so this should be used rarely - only one element in a mix can reliably set
   a size.
 
- * outputs: $IMAGE\_SIZE={size_in_GB}
+ * outputs: $IMAGE\_SIZE={size\_in\_GB}
- * inputs: $IMAGE_SIZE={size_in_GB}
+ * inputs: $IMAGE\_SIZE={size\_in\_GB}
 
 * block-device.d: customise the block device that the image will be made on
   (e.g. to make partitions).

bin/disk-image-create

@@ -41,7 +41,6 @@ INSTALL_PACKAGES=""
 COMPRESS_IMAGE="true"
 TEMP=`getopt -o a:ho:xucp: -n $SCRIPTNAME -- "$@"`
 if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi
-echo "XXX $TEMP"
 
 # Note the quotes around `$TEMP': they are essential!
 eval set -- "$TEMP"
@@ -76,13 +75,11 @@ IMAGE_ELEMENT=$($SCRIPT_HOME/element-info --expand-dependencies $IMAGE_ELEMENT)
 
 echo "Building elements: $IMAGE_ELEMENT"
 echo "If prompted for sudo, install sudoers.d/img-build-sudoers into /etc/sudoers.d and restart the build."
-mkdir -p $IMG_PATH
 
-# TODO: make an element.
+# TODO: make into an element.
 ensure_nbd
 
 mk_build_dir
-ensure_base_available
 eval_run_d block-device-size "IMAGE_SIZE="
 
 qemu-img create -f qcow2 -o preallocation=metadata $TMP_IMAGE_PATH ${IMAGE_SIZE}G

elements/ubuntu/README.md

@@ -0,0 +1 @@
+Use Ubuntu cloud images as the baseline for built disk images.

elements/ubuntu/root.d/10-cache-ubuntu-tarball

@@ -0,0 +1,22 @@
+#!/bin/bash
+# These are useful, or at worst not harmful, for all images we build.
+
+set -e
+
+[ -n "$ARCH" ]
+[ -n "$TARGET_ROOT" ]
+
+IMG_PATH=~/.cache/image-create
+CLOUD_IMAGES=${CLOUD_IMAGES:-http://cloud-images.ubuntu.com/}
+RELEASE=${RELEASE:-quantal}
+BASE_IMAGE_FILE=${BASE_IMAGE_FILE:-$RELEASE-server-cloudimg-$ARCH-root.tar.gz}
+
+mkdir -p $IMG_PATH
+# TODO: don't cache -current forever.
+if [ ! -f $IMG_PATH/$BASE_IMAGE_FILE ] ; then
+   echo "Fetching Base Image"
+   wget $CLOUD_IMAGES/$RELEASE/current/$BASE_IMAGE_FILE -O $IMG_PATH/$BASE_IMAGE_FILE.tmp
+   mv $IMG_PATH/$BASE_IMAGE_FILE.tmp $IMG_PATH/$BASE_IMAGE_FILE
+fi
+# Extract the base image
+sudo tar -C $TARGET_ROOT -xzf $IMG_PATH/$BASE_IMAGE_FILE

elements/vm/install.d/51-grub

@@ -3,7 +3,6 @@
 
 
 set -e
-set -o xtrace
 
 # XXX: grub-probe on the nbd0 device returns nothing - workaround, manually
 # specify modules. https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1073731

lib/img-defaults

@@ -15,9 +15,6 @@
 
 # options for create-baremetal-image.sh
 ARCH=${ARCH:-$(dpkg --print-architecture)}
-RELEASE=${RELEASE:-quantal}
-BASE_IMAGE_FILE=${BASE_IMAGE_FILE:-$RELEASE-server-cloudimg-$ARCH-root.tar.gz}
-CLOUD_IMAGES=${CLOUD_IMAGES:-http://cloud-images.ubuntu.com/}
 FS_TYPE=${FS_TYPE:-ext4}
 # Used to set the file extension only at this stage.
 IMAGE_TYPE=${IMAGE_TYPE:-qcow2}
@@ -25,5 +22,4 @@ IMAGE_NAME=${IMAGE_NAME:-image}
 export IMAGE_SIZE=${IMAGE_SIZE:-2} # N.B. This size is in GB
 # Set via the CLI normally. 
 # IMAGE_ELEMENT=
-IMG_PATH=~/.cache/image-create
 export ELEMENTS_DIR=$(dirname $0)/../elements

lib/img-functions

@@ -48,15 +48,6 @@ function ensure_nbd () {
     (lsmod | grep '^nbd ') || sudo modprobe nbd max_part=16
 }
 
-function ensure_base_available () {
-    # TODO: don't cache -current forever.
-    if [ ! -f $IMG_PATH/$BASE_IMAGE_FILE ] ; then
-       echo "Fetching Base Image"
-       wget $CLOUD_IMAGES/$RELEASE/current/$BASE_IMAGE_FILE -O $IMG_PATH/$BASE_IMAGE_FILE.tmp
-       mv $IMG_PATH/$BASE_IMAGE_FILE.tmp $IMG_PATH/$BASE_IMAGE_FILE
-    fi
-}
-
 function ensure_sudo () {
     sudo echo "Ensuring sudo is available"
 }
@@ -69,8 +60,17 @@ function mount_tmp_image () {
 }
 
 function create_base () {
-    # Extract the base image
+    # Copy data in to the root.
-    sudo tar -C $TMP_MOUNT_PATH -xzf $IMG_PATH/$BASE_IMAGE_FILE
+    TARGET_ROOT=$TMP_MOUNT_PATH run_d root
+
+    if [ -z "$(ls /tmp/foo)" ] ; then
+        # Nothing copied in, use Ubuntu.
+	echo "Adding ubuntu element as / had no contents"
+        IMAGE_ELEMENT=$($SCRIPT_HOME/element-info --expand-dependencies $IMAGE_ELEMENT ubuntu)
+	generate_hooks
+	echo "Now building: $IMAGE_ELEMENT"
+	TARGET_ROOT=$TMP_MOUNT_PATH run_d root
+    fi
 
     # Configure Image
     # Setup resolv.conf so we can chroot to install some packages
@@ -242,4 +242,5 @@ function do_extra_package_install () {
 function copy_elements_lib () {
   sudo mkdir -p $TMP_MOUNT_PATH/lib/diskimage-builder
   sudo cp -t $TMP_MOUNT_PATH/lib/diskimage-builder $_LIB/elements-functions
-}
+}
+