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.
 
 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
+```