Update README with repl basic documentation

README.md

@@ -7,7 +7,8 @@ A network of LXC containers, managed through libvirt
 This script will most probably break on any other system than Linux, and will
 definitely break on anything non-UNIX.
 
-It relies on `libvirt` and `overlayfs`.
+It relies on `libvirt`, `overlayfs` and `sudo` (to gain the required privileges
+to use overlayfs).
 
 ## Setup
 
@@ -43,6 +44,17 @@ You can spawn a network using
 where `topology_description.yml` is a valid topology description file (see
 below).
 
+When the network is spawned, you will get a (very basic) prompt. The available
+commands are:
+
+* `help`: display a list of available commands;
+* `exit`: cleanup the network and quit the program;
+* `dom`:
+  * `dom down`: keep the networks up, but cleanup the containers. Useful to
+    reset the containers or update binaries and settings.
+  * `dom up`: spawn the containers, if they were cleaned up beforehand.
+  * `dom restart`: equivalent to `dom down ; dom up`.
+
 ## Topology description file
 
 A topology is described in a [YAML](https://en.wikipedia.org/wiki/YAML) file