readme updated

README.md

@@ -4,3 +4,15 @@ Debootstrap for RPM Distros on Ubuntu
 Downloads SuSE environments from the openSUSE homepage and installs them into schroot environments.
 
 See [scripts/susebootstrap.sh](scripts/susebootstrap.sh).
+
+I used that to «cross compile» packages for suse and fedora on an ubuntu server. But now I don't use these scripts anymore. To get I suse build environment, I simply use docker:
+
+  docker run --rm -it opensuse bash
+
+I have special images prepared for my builds:
+
+https://hub.docker.com/r/mwaeckerlin/rpmbuildenv/
+
+  docker run --rm -it mwaeckerlin/rpmbuildenv:amd64-opensuse-leap
+
+This is all part of my [bootstrap environment](https://mrw.sh/development/bootstrap-build-environment), that installs a nice script `build-in-docker.sh`.