showmount: add page (#20627)

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

pages/common/showmount.md

@@ -0,0 +1,28 @@
+# showmount
+
+> Display mount information for an NFS server.
+> More information: <https://manned.org/showmount>.
+
+- Show clients currently mounting from the server:
+
+`showmount {{hostname}}`
+
+- Show the NFS server's export list:
+
+`showmount {{[-e|--exports]}} {{hostname}}`
+
+- Show all clients and their mounted directories:
+
+`showmount {{[-a|--all]}} {{hostname}}`
+
+- Show only the directories mounted by clients:
+
+`showmount {{[-d|--directories]}} {{hostname}}`
+
+- Show the export list without headers:
+
+`showmount {{[-e|--exports]}} --no-headers {{hostname}}`
+
+- Display help:
+
+`showmount {{[-h|--help]}}`