Add instructions how to cleanup docker images

diff --git a/README.docker.md b/README.docker.md
index 3df89db8e0d2c39080c425ce1099081b4fd20938..6232a32a6639045ce0a675810d52d0e8cc20cafe 100644 (file)
--- a/README.docker.md
+++ b/README.docker.md
@@ -2,3 +2,11 @@
 
 With docker engine there's nothing needed to configure on local system other
 than access to running docker engine and docker client program.
+
+## Maintenance
+
+To kill all containers created by cleanbuild:
+
+```shell
+docker ps -f label=cleanbuild --format '{{.ID}}' | xargs -r docker kill -q
+```