Explain how the tool must work

README.md

@@ -1,3 +1,57 @@
 # home-impermanence
 
-OpenBSD compatible implementation of the impermanence project from the NixOS community https://nixos.wiki/wiki/Impermanence
+OpenBSD compatible implementation of the [impermanence project from
+the NixOS community](https://nixos.wiki/wiki/Impermanence)
+
+Such a tool permits to have your $HOME mounted with a memory
+filesystem and populate it from an explicit list of files and
+directories hooked from a persistent storage directory, the point
+is to have a clean and reproducible environment every time you log
+in with only the content you selected.  No more extra files when
+you start a program only once.
+
+# Configuration
+
+The configuration is done in two part, system wide to configure the
+**impermanence** service that will mount the memory filesystem and
+populate it.
+
+## System wide
+
+Using rcctl: `rcctl set impermanence flags -d /home/persist/ -u
+my-user` and `rcctl enable impermanence`.
+
+## User configuration
+
+The user configuration will be done in
+`/home/persist/my-user/impermanence.yml` if you chose `-d /home/persist`
+for the service and `-u my-user`.
+
+The configuration file describes the size of the memory filesystem,
+the list of files and the list of directories that should be added
+to the filesystem as symbolic links from the persistent directory.
+
+# home-impermanence rc service
+
+## Restart
+
+The restart parameter to the service will unmount the device and
+recreate it, allowing a fresh restart.
+
+## Reload
+
+The reload parameter to the service will check the configuration
+file and will create missing links or overwrite files from the
+temporary filesystem with a symlink to the persistent storage if
+any.
+
+This should be used when you add a file or directory to your
+configuration and you want to update your current living system.
+
+## Start
+
+Creates and populates the home filesystem.
+
+## Stop
+
+Umount the home filesystem.