Create snap image

create-image.sh

#!/bin/bash
#
# Copyright (C) 2016 Canonical Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

set -ex

workdir=$(mktemp -d)
output=
kernel=
gadget=
model_assertion=
extra_snaps=
extra_devmode_snaps=
extra_assertions=
arch=
channel=stable

show_help() {
	echo "Usage: $0 [OPTIONS]"
	echo
	echo "optional arguments:"
	echo " --help:                 Show this help message and exit"
	echo " --channel:              Select another channel to use for build the image (default: $channel)"
	echo " --kernel-snap:          Kernel snap to use for building the boot image"
	echo " --gadget-snap:          Device gadget snap to use"
	echo " --model-assertion:      Model assertion file to use"
	echo " --extra-snap:           Additional snap to add to the created image. Value is directly passed to prepare-image"
	echo " --extra-assertion:      Additional assertion file to include in the image"
	echo " --output:               Target path and file name for the boot image to create"
	echo " --arch:                 Target device architecture"
}

while [ -n "$1" ]; do
	case "$1" in
		--help)
			show_help
			exit
			;;
		--channel=*)
			channel=${1#*=}
			shift
			;;
		--kernel-snap=*)
			kernel=${1#*=}
			shift
			;;
		--gadget-snap=*)
			gadget=${1#*=}
			shift
			;;
		--output=*)
			output=${1#*=}
			shift
			;;
		--model-assertion=*)
			model_assertion=${1#*=}
			shift
			;;
		--extra-snap=*)
			snap=${1#*=}
			extra_snaps="$extra_snaps --extra-snaps $snap"
			shift
			;;
		--extra-devmode-snap=*)
			snap=${1#*=}
			extra_devmode_snaps="$extra_devmode_snaps $snap"
			shift
			;;
		--extra-assertion=*)
			assert=${1#*=}
			extra_assertions="$extra_assertions $assert"
			shift
			;;
		--arch=*)
			arch=${1#*=}
			shift
			;;
		*)
			echo "Unknown command: $1"
			exit 1
			;;
	esac
done

if [ -z "$kernel" ] || [ -z "$gadget" ] || [ -z "$model_assertion" ] ; then
	echo "ERROR: Please provide a valid kernel and gadget snap and a model assertion"
	exit 1
fi

channel=stable
image_size=2G
image_name=ubuntu-core-mako
image_fs_label=writable

cp $kernel $workdir/mako-kernel.snap
cp $gadget $workdir/mako.snap

mkdir $workdir/rootfs
mkdir $workdir/rootfs/boot

snap prepare-image \
	--channel $channel \
	--extra-snaps $workdir/mako.snap \
	--extra-snaps $workdir/mako-kernel.snap \
	$extra_snaps \
	$model_assertion \
	$workdir/rootfs

sudo chown -R root:root $workdir/rootfs

mkdir $workdir/writable
mkdir $workdir/writable/system-data
cp -ra $workdir/rootfs/image/* $workdir/writable/system-data/

# Migrate all systemd units from core snap into the writable area. This
# would be normally done on firstboot by the initramfs but we can't rely
# on that because we  are adding another file in there and that will
# prevent the initramfs from transitioning any files.
core_snap=$(find $workdir/writable/system-data/var/lib/snapd/snaps -name "core_*.snap")
tmp_core=`mktemp -d`
sudo mount -o loop $core_snap $tmp_core
mkdir -p $workdir/writable/system-data/etc/systemd
cp -rav $tmp_core/etc/systemd/* \
	$workdir/writable/system-data/etc/systemd/
sudo umount $tmp_core
rm -rf $tmp_core

# system-user assertion which gives us our ubuntu:ubuntu user we use to
# log into the system
if [ -n "$extra_assertions" ]; then
	mkdir -p $workdir/writable/system-data/var/lib/snapd/seed/assertions
	for assert in $extra_assertions ; do
		cp $assert $workdir/writable/system-data/var/lib/snapd/seed/assertions/
	done
fi

# Use NetworkManager as our default network management solution
mkdir -p $workdir/writable/system-data/etc/netplan
cat << EOF > $workdir/writable/system-data/etc/netplan/00-default-nm-renderer.yaml
network:
  renderer: NetworkManager
EOF

# Disable console-conf for the first boot
mkdir -p $workdir/writable/system-data/var/lib/console-conf/
touch $workdir/writable/system-data/var/lib/console-conf/complete

# Create systemd service which is running on firstboot and sets up
# various things for us.
mkdir -p $workdir/writable/system-data/etc/systemd/system
cat << 'EOF' > $workdir/writable/system-data/etc/systemd/system/devmode-firstboot.service
[Unit]
Description=Run devmode firstboot setup
After=snapd.service snapd.socket

[Service]
Type=oneshot
ExecStart=/bin/bash -c "/bin/bash /writable/system-data/var/lib/devmode-firstboot/run.sh > /dev/console"
RemainAfterExit=yes
EOF

mkdir -p $workdir/writable/system-data/etc/systemd/system/multi-user.target.wants
ln -sf /etc/systemd/system/devmode-firstboot.service \
	$workdir/writable/system-data/etc/systemd/system/multi-user.target.wants/devmode-firstboot.service

mkdir $workdir/writable/system-data/var/lib/devmode-firstboot

cat << 'EOF' > $workdir/writable/system-data/var/lib/devmode-firstboot/run.sh
#!/bin/bash

set -ex

# Don't start again if we're already done
if [ -e /writable/system-data/var/lib/devmode-firstboot/complete ] ; then
	exit 0
fi

echo "Start devmode-firstboot $(date -Iseconds --utc)"

if [ "$(snap managed)" = "true" ]; then
	echo "System already managed, exiting"
	exit 0
fi

# no changes at all
while ! snap changes ; do
	echo "No changes yet, waiting"
	sleep 1
done

while snap changes | grep -qE '(Do|Doing) .*Initialize system state' ;  do
	echo "Initialize system state is in progress, waiting"
	sleep 1
done

if [ -n "$(snap known system-user)" ]; then
	echo "Trying to create known user"
	snap create-user --known --sudoer
fi

# Enable console-conf again
rm /writable/system-data/var/lib/console-conf/complete

# Mark us done
touch /writable/system-data/var/lib/devmode-firstboot/complete

# Reboot the system as its now prepared for the user
reboot
EOF

chmod +x $workdir/writable/system-data/var/lib/devmode-firstboot/run.sh

if [ -n "$extra_devmode_snaps" ]; then
	mkdir -p $workdir/writable/system-data/var/lib/snapd/seed/snaps/
	for snap in $extra_devmode_snaps ; do
		snap_name=
		if [ -e $snap ]; then
			cp $snap $workdir/writable/system-data/var/lib/snapd/seed/snaps/
			snap_name=`basename $snap .snap`
		else
			snap_name=`echo $snap | cut -d':' -f 1`
			if [ -z "$snap_name" ]; then
				echo "ERROR: no valid snap name provided '$snap'"
				exit 1
			fi
			snap_channel=`echo $snap | cut -d':' -f 2`
			if [ -z "$snap_channel" ]; then
				snap_channel=edge
			fi
			snap_url=`curl -H "X-Ubuntu-Series: 16" -H "X-Ubuntu-Architecture: $arch" https://search.apps.ubuntu.com/api/v1/snaps/details/$snap_name?channel=$snap_channel | jq .download_url`
			wget $snap_url -O $workdir/writable/system-data/snapd/seed/snaps/$snap_name.snap
		fi
		name=`snap info $snap | grep name | awk '{print $2}'`
		cat <<EOF >> $workdir/writable/system-data/var/lib/snapd/seed/seed.yaml
- name: $name
  unasserted: true
  devmode: true
  file: $snap_name.snap
EOF
	done
fi

(cd $workdir/writable ; tar cf $workdir/writable.tar *)
tar --numeric-owner --exclude=dev/ -tvvf $workdir/writable.tar \
	--directory $workdir > $workdir/writable.content

make_ext4fs -u / -U $workdir/writable.content -l $image_size -s \
	-L $image_fs_label $workdir/$image_name.img $workdir/writable

cp $workdir/$image_name.img $output
sudo rm -rf $workdir
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