install.sh

#!/usr/bin/env bash

set -euo pipefail

trap 'sleep infinity' EXIT

volume_mount="/runtime"

host_path=$(awk -v path="$volume_mount" '$5 == path {print $4; exit}' /proc/self/mountinfo)

if [ -z "${host_path}" ]; then
    echo "ERROR: Could not determine host path for volume ${volume_mount}"
    exit 1
fi

# Add the host mount point
# e.g /docker/volumes/1_runsc/_data -> /mnt/data/docker/volumes/1_runsc/_data
host_path="/mnt/data${host_path}"

echo "Volume host path: ${host_path}"

echo "Installing runsc runtime binaries to volume..."
rsync -av --delete /opt/ "${volume_mount}/bin/"

"${volume_mount}"/bin/runsc --version
"${volume_mount}"/bin/containerd-shim-runsc-v1 -v
echo "Binaries installed successfully!"

helper_image="${HELPER_IMAGE:-docker.io/library/alpine:latest}"

conf_path="/host/run/systemd/system/balena.service.d/runsc.conf"

# create custom drop-in to add runsc runtime to balena service
custom_conf="[Service]
Environment=\"PATH=${host_path}/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\"
Environment=\"BALENAD_EXTRA_ARGS=--add-runtime runsc=${host_path}/bin/runsc\"
"

# check if drop-in already exists and matches desired content
if docker run --rm -v /run:/host/run:ro "${helper_image}" sh -c \
    "[ -f '${conf_path}' ] && echo '${custom_conf}' > /tmp/runsc.conf.tmp && cmp -s '${conf_path}' /tmp/runsc.conf.tmp"; then
    echo "runsc runtime already registered with balena service. No changes needed."
    exit 0
fi

# install drop-in under the host OS /run path so it is cleared on reboot
echo "Installing runsc runtime drop-in to balena service..."
docker run --rm -v /run:/host/run:rw "${helper_image}" sh -c \
    "mkdir -p '$(dirname ${conf_path})' && echo '${custom_conf}' > '${conf_path}'"

# reload the systemd daemon (same as systemctl daemon-reload)
echo "Reloading systemd daemon..."
dbus-send \
    --system \
    --dest=org.freedesktop.systemd1 \
    --type=method_call \
    --print-reply \
    /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager.Reload

# restart the balena service (same as systemctl restart balena.service)
echo "Restarting balena service..."
dbus-send \
    --system \
    --dest=org.freedesktop.systemd1 \
    --type=method_call \
    --print-reply \
    /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager.RestartUnit \
    string:"balena.service" string:"replace"

echo "runsc runtime registered successfully!"