The preauthkeys commands expect a user id instead of a username

docs/setup/install/container.md

@@ -112,11 +112,11 @@ docker exec -it headscale \
 
 ### Register a machine using a pre authenticated key
 
-Generate a key using the command line:
+Generate a key using the command line for the user with ID 1:
 
 ```shell
 docker exec -it headscale \
-  headscale preauthkeys create --user myfirstuser --reusable --expiration 24h
+  headscale preauthkeys create --user 1 --reusable --expiration 24h
 ```
 
 This will return a pre-authenticated key that can be used to connect a node to headscale with the `tailscale up` command:

docs/usage/getting-started.md

@@ -117,14 +117,14 @@ headscale instance. By default, the key is valid for one hour and can only be us
 === "Native"
 
     ```shell
-    headscale preauthkeys create --user <USER>
+    headscale preauthkeys create --user <USER_ID>
     ```
 
 === "Container"
 
     ```shell
     docker exec -it headscale \
-      headscale preauthkeys create --user <USER>
+      headscale preauthkeys create --user <USER_ID>
     ```
 
 The command returns the preauthkey on success which is used to connect a node to the headscale instance via the