[users] Explain new permissions possibilities in config

src/modules/users/users.conf

@@ -215,14 +215,20 @@ allowWeakPasswordsDefault: false
 #   names for a given distro (eg. "video", or "mysql" might not be a valid
 #   end-user login name).
 # - *home_permissions* Home directory of the user is given **approximately**
-#   this set of permissions. Write the permissions in octal. If not set,
+#   this set of permissions. If not set, there is no default and no
-#   there is no default and no permission-setting is done (uses defaults of
+#   permission-setting is done (uses defaults of `useradd` in the target).
-#   `useradd` in the target). A umask is computed from these permissions
+#   A umask is computed from these permissions
-#   and passed to `useradd`. Take care to quote the numeric value.
+#   and passed to `useradd`.
+#
+#   You may write permissions as:
+#   - write "NNN" (three octal digits) or
+#   - write "oNNN" (small 'o' and three octal digits) or
+#   - write "rwxrwxrwx" (like the output of ls, with a - for unset bits)
+#   The following permissions mean the same thing: "o750", "rwxr-x---" .
 user:
   shell: /bin/bash
   forbidden_names: [ root ]
-  home_permissions: "0700"
+  home_permissions: "o700"
 
 
 # Hostname settings