Merge lp:~vorlon/livecd-rootfs/snap-in-mate into lp:livecd-rootfs

[Steve Langasek]

Generalize from live-build/ubuntu-server/hooks/032-installer-squashfs.binary handling of subiquity snap to the ability to install an arbitrary list of snaps as part of a livefs.

And install pulsemixer in the Ubuntu MATE image, per Martin Wimpress.

Ubuntu MATE build test with this change:

https://launchpad.net/~canonical-foundations/+livefs/ubuntu/artful/ubuntu-mate/+build/112019

[Martin Wimpress  (flexiondotorg)]

review: Approve

[Michael Hudson-Doyle (mwhudson)]

Looks fine, this generalizes the stuff from server-live but does not actually change server-live to use the new machinery, is there a reason for that beyond close-to-release caution?

review: Approve

[Steve Langasek (vorlon)]

Currently there are several obstacles to sort through before having server-live also use it:

- server-live installs the snap in a separate installer squashfs, not in the base livefs, which means it must be done from a binary hook. We currently have no shell libraries shared between live-build/auto/build and the hooks, and I didn't want to block this change on a refactor.
- server-live currently installs subiquity from the edge channel. While I think this should be changed, there is currently no subiquity in the stable channel, and I didn't want to block this on a subiquity promotion (nor do I want the code to support installing from non-stable channels).
- subiquity is a classic mode snap, which requires additional metadata to be provided in the seed.yaml, which I also did not want to deal with at this juncture.

[Dustin Krysak (bashfulrobot)]

This looks extremely interesting. We were considering and evaluating on how to use snaps (where appropriate) in Ubuntu Budgie. Having a method to hook into and install snaps would be amazing.

=== modified file 'debian/changelog'
--- debian/changelog	2017-10-05 23:53:11 +0000
+++ debian/changelog	2017-10-08 02:31:37 +0000
@@ -1,3 +1,10 @@
+livecd-rootfs (2.469) UNRELEASED; urgency=medium
+
+  * Add initial support for preinstallation of snaps in images, and
+    preinstall pulsemixer in the Ubuntu MATE image.
+
+ -- Steve Langasek <[e-mail]>  Fri, 06 Oct 2017 16:23:49 -0700
+
 livecd-rootfs (2.468) artful; urgency=medium
 
   [ Dimitri John Ledkov ]

=== modified file 'live-build/auto/build'
--- live-build/auto/build	2017-10-04 04:45:50 +0000
+++ live-build/auto/build	2017-10-08 02:31:37 +0000
@@ -27,6 +27,45 @@
 # Setup cleanup function
 Setup_cleanup
 
+preinstall_snaps() {
+	lb chroot_resolv install
+	chroot chroot sh -c '
+		set -x;
+		cd /var/lib/snapd/seed;
+		SNAPPY_STORE_NO_CDN=1 snap download core'
+	for snap in "$@"; do
+		chroot chroot sh -c "
+			set -x;
+			cd /var/lib/snapd/seed;
+			SNAPPY_STORE_NO_CDN=1 snap download \"$snap\""
+	done
+	lb chroot_resolv remove
+
+	CORE_SNAP=$(cd chroot/var/lib/snapd/seed; ls -1 core_*.snap)
+
+	cat <<EOF > chroot/var/lib/snapd/seed/seed.yaml
+snaps:
+ - name: core
+   channel: stable
+   file: ${CORE_SNAP}
+EOF
+	for snap in "$@"; do
+		cat <<EOF >> chroot/var/lib/snapd/seed/seed.yaml
+ - name: $snap
+   channel: stable
+EOF
+		echo -n "   file: " >> chroot/var/lib/snapd/seed/seed.yaml
+		(cd chroot/var/lib/snapd/seed; ls -1 ${snap}_*.snap) \
+			>> chroot/var/lib/snapd/seed/seed.yaml
+	done
+
+	mkdir -p chroot/var/lib/snapd/seed/snaps \
+		chroot/var/lib/snapd/seed/assertions
+	mv chroot/var/lib/snapd/seed/*.assert \
+		chroot/var/lib/snapd/seed/assertions/
+	mv chroot/var/lib/snapd/seed/*.snap chroot/var/lib/snapd/seed/snaps/
+}
+
 rm -f binary.success
 (
 	if [ -d config/gnupg ]; then
@@ -322,6 +361,17 @@
 			;;
 	esac
 
+	# FIXME: this should not be a hard-coded list in this script; this
+	# is an interim solution for 17.10.
+	case $PROJECT:$SUBPROJECT in
+		ubuntu-mate:*)
+			SNAP_LIST=pulsemixer
+			;;
+	esac
+	if [ -n "$SNAP_LIST" ]; then
+		preinstall_snaps $SNAP_LIST
+	fi
+
 	if [ "$PROJECT" = "ubuntu-touch" ] || [ "$PROJECT" = "ubuntu-touch-custom" ]; then
 		if [ "$ARCH" = "armhf" ]; then
 			INFO_DESC="$(lsb_release -d -s)"