Add support for snapshots/restore on OS level (#801)

buildroot-external/rootfs-overlay/etc/systemd/system/docker.service.d/hassos.conf

@@ -1,5 +1,5 @@
 [Unit]
-RequiresMountsFor=/etc/docker /mnt/data
+RequiresMountsFor=/etc/docker /mnt/data /var/lib/docker
 
 [Service]
 ExecStart=

buildroot-external/rootfs-overlay/usr/lib/systemd/system/hassos-supervisor.service

@@ -3,7 +3,7 @@ Description=HassOS supervisor
 Requires=docker.service
 Wants=network-online.target
 After=docker.service rauc.service dbus.socket network-online.target
-RequiresMountsFor=/mnt/data
+RequiresMountsFor=/mnt/data /mnt/boot /mnt/overlay
 StartLimitIntervalSec=60
 StartLimitBurst=5
 

buildroot-external/rootfs-overlay/usr/sbin/hassos-supervisor

@@ -79,7 +79,9 @@ if [ -z "${SUPERVISOR_CONTAINER_ID}" ]; then
         -v /var/run/docker.sock:/var/run/docker.sock \
         -v /var/run/dbus:/var/run/dbus \
         -v /etc/machine-id:/etc/machine-id:ro \
-        -v ${SUPERVISOR_DATA}:/data \
+        -v ${SUPERVISOR_DATA}:/data:rw \
+        -v /mnt/overlay:/os/overlay:rw \
+        -v /mnt/boot:/os/boot:rw \
         -e SUPERVISOR_SHARE=${SUPERVISOR_DATA} \
         -e SUPERVISOR_NAME=hassio_supervisor \
         -e SUPERVISOR_MACHINE=${SUPERVISOR_MACHINE} \