docker: add systemd service file

Some options of docker.service are commented out, because they currently
don't work on our system (to old systemd).

We want to start docker only on demand.

docker.be0

@@ -1,6 +1,6 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION docker-1.12.1-0.bee
+# BEE_VERSION docker-1.12.1-1.bee
 
 # NOTE: We require a running docker environment. For the first bootstrap
 # this can be provided by the package docker_binary
@@ -69,6 +69,7 @@ mee_build() {
 mee_install() {
     install --directory $D$BINDIR
     install --directory $D$SYSCONFDIR/default
+    install --directory $D$SYSCONFDIR/systemd/system
 
     V=$PKGVERSION
 
@@ -90,6 +91,38 @@ mee_install() {
     cat >$D$SYSCONFDIR/default/docker <<-'__EOF__'
 	DOCKER_OPTS="--storage-driver=overlay2"
 	__EOF__
+
+    cat >$D$SYSCONFDIR/systemd/system/docker.service <<-'__EOF__'
+	[Unit]
+	Description=Docker Application Container Engine
+	#Documentation=https://docs.docker.com
+	After=network.target
+
+	[Service]
+	Type=notify
+	# the default is not to use systemd for cgroups because the delegate issues still
+	# exists and systemd currently does not support the cgroup feature set required
+	# for containers run by docker
+	ExecStart=/usr/bin/dockerd
+	ExecReload=/bin/kill -s HUP $MAINPID
+	# Having non-zero Limit*s causes performance problems due to accounting overhead
+	# in the kernel. We recommend using cgroups to do container-local accounting.
+	#LimitNOFILE=infinity
+	#LimitNPROC=infinity
+	#LimitCORE=infinity
+	# Uncomment TasksMax if your systemd version supports it.
+	# Only systemd 226 and above support this version.
+	#TasksMax=infinity
+	#TimeoutStartSec=0
+	# set delegate yes so that systemd does not reset the cgroups of docker containers
+	#Delegate=yes
+	# kill only the docker process, not all processes in the cgroup
+	KillMode=process
+	StandardOutput=syslog
+
+	[Install]
+	#WantedBy=multi-user.target
+	__EOF__
 }
 
 ## by default this may be 'make install DESTDIR="${D}"'