uuid: add page, uuidgen: update description (#5892)

pages/linux/uuidgen.md

@@ -1,15 +1,17 @@
 # uuidgen
 
 > Generate unique identifiers (UUIDs).
+> See also `uuid`.
+> More information: <https://manned.org/uuidgen>.
 
-- Create a random UUID:
+- Create a random UUIDv4:
 
 `uuidgen --random`
 
-- Create a UUID based on the current time:
+- Create a UUIDv1 based on the current time:
 
 `uuidgen --time`
 
-- Create a UUID based on the hash of a URL:
+- Create a UUIDv5 of the name with a specified namespace prefix:
 
-`uuidgen --sha1 --namespace {{@url}} --name {{object_name}}`
+`uuidgen --sha1 --namespace {{@dns|@url|@oid|@x500}} --name {{object_name}}`