Update Readme

Signed-off-by: Roger Pueyo Centelles <roger.pueyo@guifi.net>

README.md

@@ -98,7 +98,14 @@ The `monitors` *set* in the `guifi` *bucket* is an `array` of `strings`, each `s
 $ curl localhost:3000/set/read/guifi/monitors
   ["0","1","2"]
 ```
+When started, each of the monitoring instances register to the system by adding their `ID` to this *set*.
 
+##### guifi (bucket) => checksum (LWW<sup>1</sup> register)
+The `checksum` *LWW register* in the `guifi` *bucket* is a `strings` containing the *SHA256 checksum* of the CNML data fetched from the Guifi.net website and pushed to the database. For example:
+```bash
+$ curl localhost:3000/register/read/guifi/checksum
+  35aaa826b841ed412897691bb1f50278d742ef9a76da9750a8ae509d3b01f8ee
+```
 
 #### device-i (bucket)
 The `device-i` bucket, where `i` is the numeric `ID` of a device in the `guifi/devices` set, contains the information about a Guifi.net device:
@@ -116,7 +123,8 @@ The `monitors` *set* in the `device-i` *bucket* is an `array` of `strings`, each
 $ curl localhost:3000/set/read/device-26932/monitors
   ["a45632","21435","a47363"]
 ```
-##### device-i (bucket) => graphserver (LWW<sup>1</sup> register)
+
+##### device-i (bucket) => graphserver (LWW register)
 The `graphserver` *LWW register* in the `device-i` *bucket* is a `string` containing the ID of a monitor the device is assigned to **in the Guifi.net** website (i.e., not automatically assigned by the monitoring application, but done manually on the Guifi.net website, and included in the CNML). For example:
 
 ```bash