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#!/bin/bash
# mount ubuntu cloud image through qemu-nbd and mount
# critical virtual filesystems (such as proc) under
# the root of mounted image.
# The path of the image needs to be absolute as a systemd service
# gets created for qemu-nbd.
mount_ubuntu_image() {
local CLOUD_IMAGE=$1
local IMAGE_MOUNTPOINT=$2
if ! lsmod | grep nbd; then
modprobe nbd
fi
# Run qemu-nbd as a service, so that it does not interact with ssh
# stdin/stdout it would otherwise inherit from the spread session.
systemd-run --system --service-type=forking --unit=qemu-nbd-preseed.service "$(command -v qemu-nbd)" -v --fork -c /dev/nbd0 "$CLOUD_IMAGE"
# nbd0p1 may take a short while to become available
if ! retry -n 30 --wait 1 test -e /dev/nbd0p1; then
echo "ERROR: /dev/nbd0p1 did not show up"
journalctl -u qemu-nbd-preseed.service
find /dev/ -name "nbd0*" -ls
exit 1
fi
mount /dev/nbd0p1 "$IMAGE_MOUNTPOINT"
mount -t proc /proc "$IMAGE_MOUNTPOINT/proc"
mount -t sysfs sysfs "$IMAGE_MOUNTPOINT/sys"
mount -t devtmpfs udev "$IMAGE_MOUNTPOINT/dev"
mount -t securityfs securityfs "$IMAGE_MOUNTPOINT/sys/kernel/security"
}
umount_ubuntu_image() {
local IMAGE_MOUNTPOINT=$1
for fs in proc dev sys/kernel/security sys; do
umount "$IMAGE_MOUNTPOINT/$fs"
done
umount "$IMAGE_MOUNTPOINT"
rmdir "$IMAGE_MOUNTPOINT"
# qemu-nbd -d may sporadically fail when removing the device,
# reporting it's still in use.
retry -n 5 --wait 1 qemu-nbd -d /dev/nbd0
}
# inject_snap_info_seed adds a snap to the seed.yaml, and works for snaps not
# already in the seed. It requires base snaps, default-providers, etc. to all be
# worked out and manually added with additional invocations
# the first argument is the mountpoint of the image, the second argument is the
# name of the snap, the snap file must be the same as the name with .snap as the
# file extension in the current working directory
# example:
# $ snap download --edge --basename=test-snapd-sh test-snapd-sh
# $ inject_snap_into_seeds "$IMAGE_MOUNTPOINT" test-snapd-sh
inject_snap_into_seed() {
local IMAGE_MOUNTPOINT=$1
local SNAP_NAME=$2
local SNAP_FILE="$SNAP_NAME.snap"
local SEED_DIR="$IMAGE_MOUNTPOINT/var/lib/snapd/seed"
local SEED_YAML="$SEED_DIR/seed.yaml"
local SEED_SNAPS_DIR="$SEED_DIR/snaps"
# Ubuntu 24.04: there is no longer any seeded snaps in base or minimal cloud images
# https://bugs.launchpad.net/ubuntu/+source/ubuntu-meta/+bug/2051346
# https://bugs.launchpad.net/ubuntu/+source/ubuntu-meta/+bug/2051572
if [ ! -d "$SEED_DIR" ]; then
snap known model > /tmp/generic.model
snap prepare-image --classic /tmp/generic.model "$IMAGE_MOUNTPOINT"
fi
# need remarshal for going from json to yaml and back for seed manipulation
if ! command -v json2yaml || ! command -v yaml2json; then
snap install remarshal
fi
# XXX: this is very simplistic and will break easily, refactor to use the
# iterative seed modification prepare-image args when those exist
# shellcheck disable=SC2016
snapsWithName=$(gojq --yaml-input -r --arg NAME "$SNAP_NAME" '[.snaps[] | select(.name == $NAME)] | length' < "$SEED_YAML")
if [ "$snapsWithName" != "0" ]; then
# get the snap file name so we can delete it from the seed
# shellcheck disable=SC2016
old_name=$(gojq --yaml-input -r --arg NAME "$SNAP_NAME" '.snaps[] | select(.name == $NAME) | .file' < "$SEED_YAML")
rm "$SEED_SNAPS_DIR/$old_name"
# now drop the entry from the seed.yaml so we can add the new one easily
# shellcheck disable=SC2016
gojq --yaml-input --yaml-output --arg NAME "$SNAP_NAME" \
'del(.snaps[] | select(.name == $NAME))' < "$SEED_YAML" > "$SEED_YAML.tmp"
mv "$SEED_YAML.tmp" "$SEED_YAML"
fi
# now add the desired snap as an unasserted snap with some jq magic™
# shellcheck disable=SC2016
gojq --yaml-input --yaml-output --arg FILE "$SNAP_FILE" --arg NAME "$SNAP_NAME" \
'.snaps[.snaps| length] |= . + {"channel":"stable","unasserted":true,"name":$NAME,"file":$FILE}' < "$SEED_YAML" > "$SEED_YAML.tmp"
mv "$SEED_YAML.tmp" "$SEED_YAML"
# and remember to copy the new snap file to the seed
cp "$SNAP_FILE" "$SEED_SNAPS_DIR"
# check that we didn't break things too badly
snap debug validate-seed "$SEED_YAML"
}
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