Build images using loopdev instead of qemu-nbd.

Qemu-nbd does not perform well with older versions of qemu due to
the lack of writeback caching mode. It also only builds qcow2 images
and there is a desire for raw image support. Finally, qemu-nbd makes
it very difficult to build images concurrently due to the somewhat
opaque nature of how it selects a /dev/nbd# device. losetup, on
the other hand, makes this process very straight forward.

Change-Id: I309fad8af4fd1e8d1720c17b65e1897a76d5e897
Co-Author: Clint Byrum <clint@fewbar.com>

.gitignore

@@ -6,3 +6,4 @@
 *.egg-info
 dist
 *.qcow2
+*.raw

README.md

@@ -50,8 +50,10 @@ Images are built using a chroot and bind mounted /proc /sys and /dev. The goal
 of the image building process is to produce blank slate machines that have all
 the necessary bits to fulfill a specific purpose in the running of an Openstack
 cloud: e.g. a nova-compute node. Images produce either a filesystem image with
-a label of cloudimg-rootfs, or can be customised to produce disk images (but
+a label of cloudimg-rootfs, or can be customised to produce whole disk images
-will still contain a filesystem labelled cloudimg-rootfs).
+(but will still contain a filesystem labelled cloudimg-rootfs). Once the file
+system tree is assembled a loopback device with filesystem (or partition table
+and file system) is created and the tree copied into it.
 
 An element is a particular set of code that alters how the image is built, or
 runs within the chroot to prepare the image. E.g. the local-config element
@@ -83,7 +85,7 @@ contents can be modelled as three distinct portions:
   nova instance disk images, disk image cache. These would typically be stored
   on a dedicated partition and not overwritten when re-deploying the image.
 
-The goal of the image building tools is to create machine images that content
+The goal of the image building tools is to create machine images that contain
 the correct global content and are ready for 'last-mile' configuration by the
 nova metadata API, after which a configuration management system can take over
 (until the next deploy, when it all starts over from scratch). 
@@ -120,27 +122,27 @@ part of the process you need to customise:
 
  * inputs: $ARCH=i386|amd64|armhf $TARGET\_ROOT=/path/to/target/workarea
 
-* cleanup.d: Perform cleanups of the root filesystem content. For instance,
+* finalise.d: Perform final tuning of the root filesystem. Runs in a chroot
-  temporary settings to use the image build environment HTTP proxy are removed
+  after the root filesystem content has been copied into the mounted
-  here in the dpkg element. Runs outside the chroot on the host environment.
+  filesystem: this is an appropriate place to reset SELinux metadata, install
+  grub bootloaders and so on. Because this happens inside the final image, it
+  is important to limit operations here to only those necessary to affect the
+  filesystem metadata and image itself. For most operations, post-install.d
+  is preferred.
+
+* cleanup.d: Perform cleanup of the root filesystem content. For
+  instance, temporary settings to use the image build environment HTTP proxy
+  are removed here in the dpkg element. Runs outside the chroot on the host
+  environment.
 
  * inputs: $ARCH=i386|amd64|armhf $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.
-  NB: Due to the current simple implementation, the last output value wins
-  so this should be used rarely - only one element in a mix can reliably set
-  a size.
-
- * outputs: $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).
+  (e.g. to make partitions). Runs outside the chroot, after the target tree
+  has been fully populated but before the cleanup hook runs.
 
  * outputs: $IMAGE\_BLOCK\_DEVICE={path}
- * inputs: $IMAGE\_BLOCK\_DEVICE={path}
+ * inputs: $IMAGE\_BLOCK\_DEVICE={path} $TARGET\_ROOT={path}
 
 * extra-data.d: pull in extra data from the host environment that hooks may
   need during image creation. This should copy any data (such as SSH keys,

bin/disk-image-create

@@ -94,22 +94,6 @@ echo "If prompted for sudo, install sudoers.d/img-build-sudoers into /etc/sudoer
 ensure_nbd
 
 mk_build_dir
-eval_run_d block-device-size "DIB_IMAGE_SIZE="
-
-qemu-img create -f qcow2 -o preallocation=metadata $TMP_IMAGE_PATH ${DIB_IMAGE_SIZE}G
-
-# grab the next available /dev/nbdX and connect to it
-map_nbd $TMP_IMAGE_PATH
-echo "NBD Device: $NBD_DEV"
-
-export EXTRA_UNMOUNT="sudo qemu-nbd -d $NBD_DEV"
-export IMAGE_BLOCK_DEVICE=$NBD_DEV
-eval_run_d block-device "IMAGE_BLOCK_DEVICE="
-
-sudo mkfs -F -t $FS_TYPE -L cloudimg-rootfs ${IMAGE_BLOCK_DEVICE}
-
-mount_tmp_image ${IMAGE_BLOCK_DEVICE}
-
 create_base
 run_d extra-data
 # Run pre-install scripts. These do things that prepare the chroot for package installs
@@ -119,6 +103,27 @@ do_extra_package_install
 run_d_in_target install
 run_d_in_target post-install
 prepare_first_boot
+# Free up /mnt
+unmount_image
+mv $TMP_BUILD_DIR/mnt $TMP_BUILD_DIR/built
+# in kb*0.8 - underreport to get a slightly bigger device
+_NEEDED_SIZE=$(sudo du --block-size=800 -x -s ${TMP_BUILD_DIR}/built | awk ' { print $1 } ')
+truncate -s${_NEEDED_SIZE}K $TMP_IMAGE_PATH
+LOOPDEV=$(sudo losetup --show -f $TMP_IMAGE_PATH)
+export EXTRA_UNMOUNT="sudo losetup -d $LOOPDEV"
+export IMAGE_BLOCK_DEVICE=$LOOPDEV
+eval_run_d block-device "IMAGE_BLOCK_DEVICE="
+OPTS=""
+if [ "$FS_TYPE" = "ext4" ] ; then
+    # Very conservative to handle images being resized a lot
+    OPTS="-i 4096"
+fi
+sudo mkfs $OPTS -t $FS_TYPE -L cloudimg-rootfs ${IMAGE_BLOCK_DEVICE}
+mkdir $TMP_BUILD_DIR/mnt
+sudo mount ${IMAGE_BLOCK_DEVICE} $TMP_BUILD_DIR/mnt
+sudo mv -t $TMP_BUILD_DIR/mnt ${TMP_BUILD_DIR}/built/*
+mount_proc_dev_sys
+run_d_in_target finalise
 finalise_base
 unmount_image
 compress_image

elements/fedora/bin/map-packages

@@ -21,6 +21,7 @@ import sys
 # distromatch or other rich data sources.
 # Debian name on the left, Fedora on the right.
 package_map = {
+    'grub-pc': 'grub2-tools grub2',
     'linux-image-generic': 'kernel',
     'open-iscsi': 'iscsi-initiator-utils',
     'vlan': 'vconfig',

elements/fedora/pre-install.d/15-fedora-remove-grub

@@ -2,12 +2,14 @@
 
 set -e
 
-GRUB_CFG=/boot/grub2/grub.cfg
+yum remove -y grub2-tools
 
-[ -f "$GRUB_CFG" ]
+#GRUB_CFG=/boot/grub2/grub.cfg
+
+#[ -f "$GRUB_CFG" ]
 
 # Update the config to have the search UUID of the image being built.
 # When partition staging is moved to a separate stage, this will need to happen
 # there. This generates a non-UUID config, which is irrelevant for booting with
 # hypervisor kernel + ramdisk, and fixed up by 51-grub for vm images.
-GRUB_DISABLE_LINUX_UUID=true grub2-mkconfig -o $GRUB_CFG
+#GRUB_DISABLE_LINUX_UUID=true grub2-mkconfig -o $GRUB_CFG

elements/fedora/root.d/10-fedora-cloud-image

@@ -43,3 +43,4 @@ if [ ! -f $IMG_PATH/$BASE_IMAGE_TAR ] ; then
 fi
 # Extract the base image
 sudo tar -C $TARGET_ROOT -xzf $IMG_PATH/$BASE_IMAGE_TAR
+sudo rmdir $TARGET_ROOT/lost+found

elements/ubuntu/pre-install.d/00-remove-grub

@@ -0,0 +1,8 @@
+#!/bin/bash
+# The grub post-kernel install hook will barf if the block device can't be
+# found (as happens in a chroot).
+# Temporarily remove grub, to avoid that confusion.
+
+set -e
+
+apt-get -y remove grub-pc grub2-common

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

@@ -27,3 +27,4 @@ if [ ! -f $IMG_PATH/$BASE_IMAGE_FILE ] ; then
 fi
 # Extract the base image
 sudo tar -C $TARGET_ROOT -xzf $IMG_PATH/$BASE_IMAGE_FILE
+sudo rmdir $TARGET_ROOT/lost+found

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

@@ -13,4 +13,6 @@ sudo sfdisk $IMAGE_BLOCK_DEVICE << EOF
 0 0;
 EOF
 
+sudo partprobe $IMAGE_BLOCK_DEVICE
+
 echo "IMAGE_BLOCK_DEVICE=${IMAGE_BLOCK_DEVICE}p1"

elements/vm/finalise.d/51-grub

@@ -4,20 +4,25 @@
 # different distributions gracefully.
 
 set -e
+set -x
 
-# XXX: grub-probe on the nbd0 device returns nothing - workaround, manually
+install-packages grub-pc
+
+# XXX: grub-probe on the nbd0/loop0 device returns nothing - workaround, manually
 # specify modules. https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1073731
 GRUBNAME=`which grub-install` || echo "trying grub2-install"
 if [ -z "$GRUBNAME" ]; then
-    GRUBNAME=`which grub2-install`
+    GRUBNAME="bash -x `which grub2-install`"
 fi
 if [ -z "$GRUBNAME" ]; then
     echo "NO grub-install or grub2-install found"
     exit 1
 fi
-BOOT_DEV=/dev/nbd0
+# FIXME:
-PART_DEV=/dev/nbd0p1
+[ -n "$IMAGE_BLOCK_DEVICE" ]
-$GRUBNAME --modules="biosdisk part_msdos" $BOOT_DEV
+PART_DEV=$IMAGE_BLOCK_DEVICE
+BOOT_DEV=$(echo $IMAGE_BLOCK_DEVICE | sed -e 's/p1//')
+$GRUBNAME --target=i386-pc --modules="biosdisk part_msdos" $BOOT_DEV
 # This might be better factored out into a per-distro 'install-bootblock'
 # helper.
 if [ -f "/boot/grub/grub.cfg" ] ; then
@@ -30,3 +35,6 @@ fi
 # NOTE: Updating the grub config by hand once deployed should work, its just
 # prepping it in a different environment that needs fiddling.
 sed -i "s%$PART_DEV%LABEL=cloudimg-rootfs%" $GRUB_CFG
+sed -i "s%search --no-floppy --fs-uuid --set=root .*$%search --no-floppy --set=root --label cloudimg-rootfs%" $GRUB_CFG
+sed -i "s%root=UUID=[A-Za-z0-9\-]*%root=LABEL=cloudimg-rootfs%" $GRUB_CFG
+

lib/common-functions

@@ -16,9 +16,11 @@
 function mk_build_dir () {
   export TMP_BUILD_DIR=$(mktemp -t -d --tmpdir=${TMP_DIR:-/tmp} image.XXXXXXXX)
   [ $? -eq 0 ] || die "Failed to create tmp directory"
+  sudo mount -t tmpfs tmpfs $TMP_BUILD_DIR
+  sudo chown $(id -u):$(id -g) $TMP_BUILD_DIR
   trap cleanup EXIT
   echo Building in $TMP_BUILD_DIR
-  export TMP_IMAGE_PATH=$TMP_BUILD_DIR/image
+  export TMP_IMAGE_PATH=$TMP_BUILD_DIR/image.raw
   export TMP_HOOKS_PATH=$TMP_BUILD_DIR/hooks
 }
 
@@ -30,7 +32,7 @@ function save_image () {
     fi
 
     cp $TMP_IMAGE_PATH $1
-    rm -r $TMP_BUILD_DIR
+    cleanup_dirs
     # All done!
     trap EXIT
     echo "Image file $1 created..."

lib/img-functions

@@ -25,8 +25,8 @@ function unmount_image () {
     sleep 5
     # oh ya don't want to forget to unmount the image
     sudo umount -f $TMP_BUILD_DIR/mnt || true
-    # having disk corruption issues; one possibility is qemu-nbd not flush dirty
+    # having disk corruption issues; one possibility is qemu-nbd not flushing
-    # pages on disconnect?
+    # dirty pages on disconnect?
     sync
     if [ -n "$EXTRA_UNMOUNT" ]; then
         $EXTRA_UNMOUNT
@@ -35,6 +35,13 @@ function unmount_image () {
 
 function cleanup () {
     unmount_image
+    cleanup_dirs
+}
+
+function cleanup_dirs () {
+    sudo rm -rf $TMP_BUILD_DIR/built
+    sudo rm -rf $TMP_BUILD_DIR/mnt
+    sudo umount $TMP_BUILD_DIR
     rm -rf $TMP_BUILD_DIR
 }
 
@@ -52,14 +59,9 @@ function ensure_sudo () {
     sudo echo "Ensuring sudo is available"
 }
 
-function mount_tmp_image () {
-  mkdir $TMP_BUILD_DIR/mnt
-  sudo mount $@ $TMP_BUILD_DIR/mnt
-  [ $? -eq 0 ] || die "Failed to mount image"
-  export TMP_MOUNT_PATH=$TMP_BUILD_DIR/mnt
-}
-
 function create_base () {
+    mkdir $TMP_BUILD_DIR/mnt
+    export TMP_MOUNT_PATH=$TMP_BUILD_DIR/mnt
     # Copy data in to the root.
     TARGET_ROOT=$TMP_MOUNT_PATH run_d root
     if [ -z "$(ls $TMP_MOUNT_PATH | grep -v lost+found)" ] ; then
@@ -92,12 +94,14 @@ function create_base () {
     else
         echo nameserver 8.8.8.8 > $TMP_MOUNT_PATH/etc/resolv.conf
     fi
+    mount_proc_dev_sys
+}
 
+function mount_proc_dev_sys () {
     # supporting kernel file systems
     sudo mount -t proc none $TMP_MOUNT_PATH/proc
     sudo mount --bind /dev $TMP_MOUNT_PATH/dev
     sudo mount -t sysfs none $TMP_MOUNT_PATH/sys
-
 }
 
 # Helper function to run a command inside the chroot
@@ -167,7 +171,7 @@ function finalise_base () {
 function compress_image () {
     # Recreate our image to throw away unnecessary data
     test $IMAGE_TYPE != qcow2 && COMPRESS_IMAGE=""
-    qemu-img convert ${COMPRESS_IMAGE:+-c} $TMP_IMAGE_PATH -O $IMAGE_TYPE $TMP_IMAGE_PATH-new
+    qemu-img convert ${COMPRESS_IMAGE:+-c} -f raw $TMP_IMAGE_PATH -O $IMAGE_TYPE $TMP_IMAGE_PATH-new
     rm $TMP_IMAGE_PATH
     mv $TMP_IMAGE_PATH-new $TMP_IMAGE_PATH
 }

sudoers.d/img-build-sudoers

@@ -24,9 +24,12 @@ ALL ALL=(root) NOPASSWD: /bin/mount -o remount\,ro\,bind /tmp/*/hooks /tmp/*/mnt
 ALL ALL=(root) NOPASSWD: /bin/mount -t proc none /tmp/*/mnt/proc
 ALL ALL=(root) NOPASSWD: /bin/mount -t sysfs none /tmp/*/mnt/sys
 ALL ALL=(root) NOPASSWD: /bin/mount /dev/nbd0* /tmp/*/mnt
-ALL ALL=(root) NOPASSWD: /bin/mount /dev/loop*p* /tmp/*/mnt
+ALL ALL=(root) NOPASSWD: /bin/mount /dev/loop* /tmp/*/mnt
 ALL ALL=(root) NOPASSWD: /bin/mv /tmp/*/mnt/* /tmp/*/mnt/*
+ALL ALL=(root) NOPASSWD: /bin/mv -t /tmp/*/mnt /tmp/*/built/*
+ALL ALL=(root) NOPASSWD: /bin/rm -* /tmp/*/mnt
 ALL ALL=(root) NOPASSWD: /bin/rm -* /tmp/*/mnt/*
+ALL ALL=(root) NOPASSWD: /bin/rm -* /tmp/*/built
 ALL ALL=(root) NOPASSWD: /bin/rmdir /tmp/*/mnt/*
 ALL ALL=(root) NOPASSWD: /bin/tar -C /tmp/*/mnt -xzf /*/.cache/image-create/*
 ALL ALL=(root) NOPASSWD: /bin/umount -f /tmp/*/mnt
@@ -34,9 +37,10 @@ ALL ALL=(root) NOPASSWD: /bin/umount -f /tmp/*/mnt/dev
 ALL ALL=(root) NOPASSWD: /bin/umount -f /tmp/*/mnt/proc
 ALL ALL=(root) NOPASSWD: /bin/umount -f /tmp/*/mnt/sys
 ALL ALL=(root) NOPASSWD: /bin/umount -f /tmp/*/mnt/tmp/in_target.d
-ALL ALL=(root) NOPASSWD: /sbin/mkfs -F -t ext4 -L cloudimg-rootfs /dev/nbd0*
+ALL ALL=(root) NOPASSWD: /sbin/mkfs -i 4096 -t ext4 -L cloudimg-rootfs /dev/loop*
 ALL ALL=(root) NOPASSWD: /sbin/modprobe nbd max_part=16
-ALL ALL=(root) NOPASSWD: /sbin/sfdisk /dev/nbd0
+ALL ALL=(root) NOPASSWD: /sbin/sfdisk /dev/nbd*
+ALL ALL=(root) NOPASSWD: /sbin/sfdisk /dev/loop*
 ALL ALL=(root) NOPASSWD: /usr/bin/qemu-nbd -c /dev/nbd0 --cache=writeback /tmp/*/image
 ALL ALL=(root) NOPASSWD: /usr/bin/qemu-nbd -d /dev/nbd0
 ALL ALL=(root) NOPASSWD: /usr/bin/touch /tmp/*/mnt/*
@@ -45,6 +49,10 @@ ALL ALL=(root) NOPASSWD: /bin/cp -t /tmp/*/mnt/etc/ -a /tmp/*/hooks/first-boot.d
 ALL ALL=(root) NOPASSWD: /usr/bin/install -m 0755 -o root -g root -D */dib-run-parts /tmp/*/mnt/usr/local/bin/dib-run-parts
 ALL ALL=(root) SETENV: NOPASSWD: /usr/sbin/chroot /tmp/*/mnt *
 ALL ALL=(root) NOPASSWD: /sbin/losetup --show -r -f /tmp/*/*.raw
-ALL ALL=(root) NOPASSWD: /sbin/losetup -d /dev/loop*
+ALL ALL=(root) NOPASSWD: /sbin/losetup --show -f /tmp/*/*.raw
 ALL ALL=(root) NOPASSWD: /sbin/losetup -d /dev/loop*
 ALL ALL=(root) NOPASSWD: /sbin/partprobe /dev/loop*
+ALL ALL=(root) NOPASSWD: /usr/bin/du --block-size=* -x -s /tmp/*/built
+ALL ALL=(root) NOPASSWD: /bin/mount -t tmpfs tmpfs /tmp/image.*
+ALL ALL=(root) NOPASSWD: /bin/umount /tmp/image.*
+ALL ALL=(root) NOPASSWD: /bin/chown *\:* /tmp/image.*