diff --git a/README.md b/README.md
index 5770844496bd3f6d87156802fabaef9f5bfe052e_UkVBRE1FLm1k..ce0d4b8488c4326e861208d35c5e11ea100022cb_UkVBRE1FLm1k 100644
--- a/README.md
+++ b/README.md
@@ -8,4 +8,15 @@
 Usage
 -----
 
-See `./run --help`
+See `./run --help` and `./run <subcommand> --help`
+
+
+Cleanup
+-------
+
+`hg clean -i tmp` is safe to run any time Megafine is not running.
+It should usually do nothing, but might if a process was interrupted.
+
+`hg clean -i cache`  is safe to run any time Megafine is not running,
+at the cost of CPU time and/or network traffic
+to rebuild parts as they become needed again.