+## Advanced Usage
+
+There are several environtment variables which can be used to modify the behavior of
+the image. Those can be listed using `frr-topotests -h`.
+
+For example, a volume is used to cache build artifacts between multiple runs
+of the image. If you need to force a complete recompile, you can set `TOPOTEST_CLEAN`:
+
+```console
+TOPOTEST_CLEAN=1 frr-topotests
+```
+
+By default, `frr-topotests` will execute pytest without any arguments. If you append an
+arguments with the first one starting with `/` or `./`, they will replace the call to
+pytest. If the appended arguments do not match this patttern, they will be provided to
+pytest as arguments.
+
+So, to run a specific test with more verbose logging:
+
+```console
+frr-topotests -vv -s all-protocol-startup/test_all_protocol_startup.py
+```
+
+And to compile FRR but drop into a shell instead of running pytest:
+
+```console
+frr-topotests /bin/bash
+```