added description on clean up

evshvarov · web-flow · commit 4a659b3ce3e7 · 2021-02-16T13:02:19.000+03:00
diff --git a/dev.md b/dev.md
@@ -1,5 +1,6 @@
 # useful commands
 ## clean up docker 
+use it when docker says "There is no space left on device". It will remove built but not used images and other temporary files.
 ```
 docker system prune -f
 ```
