groupadd, groupdel, groupmod, groups: update page (#7660)

pages/linux/groupadd.md

@@ -1,12 +1,17 @@
 # groupadd
 
 > Add user groups to the system.
+> See also: `groups`, `groupdel`, `groupmod`.
 > More information: <https://manned.org/groupadd>.
 
-- Create a new Linux group:
+- Create a new group:
 
-`groupadd {{group_name}}`
+`sudo groupadd {{group_name}}`
 
-- Create new group with a specific groupid:
+- Create a new system group:
 
-`groupadd {{group_name}} -g {{group_id}}`
+`sudo groupadd --system {{group_name}}`
+
+- Create a new group with the specific groupid:
+
+`sudo groupadd --gid {{id}} {{group_name}}`