Documentation: nfs: idmapper: convert to ReST

Convert idmapper.txt to ReST and move it to admin-guide.
Content remains mostly unchanged otherwise.
Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
Link: https://lore.kernel.org/r/069e40cd551ea778538f8fe9ad15ee26e45fc748.1578697871.git.dwlsalmeida@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/nfs/index.rst

@@ -9,3 +9,4 @@ NFS
     nfsroot
     nfs-rdma
     nfsd-admin-interfaces
+    nfs-idmapper

Documentation/filesystems/nfs/idmapper.txt → Documentation/admin-guide/nfs/nfs-idmapper.rst

+=============
+NFS ID Mapper
+=============
 
-=========
-ID Mapper
-=========
 Id mapper is used by NFS to translate user and group ids into names, and to
 translate user and group names into ids.  Part of this translation involves
 performing an upcall to userspace to request the information.  There are two
@@ -20,22 +20,24 @@ legacy rpc.idmap daemon for the id mapping.  This result will be stored
 in a custom NFS idmap cache.
 
 
-===========
 Configuring
 ===========
+
 The file /etc/request-key.conf will need to be modified so /sbin/request-key can
 direct the upcall.  The following line should be added:
 
-#OP	TYPE	DESCRIPTION	CALLOUT INFO	PROGRAM ARG1 ARG2 ARG3 ...
-#======	=======	===============	===============	===============================
-create	id_resolver	*	*		/usr/sbin/nfs.idmap %k %d 600
+``#OP	TYPE	DESCRIPTION	CALLOUT INFO	PROGRAM ARG1 ARG2 ARG3 ...``
+``#======	=======	===============	===============	===============================``
+``create	id_resolver	*	*		/usr/sbin/nfs.idmap %k %d 600``
+
 
 This will direct all id_resolver requests to the program /usr/sbin/nfs.idmap.
 The last parameter, 600, defines how many seconds into the future the key will
 expire.  This parameter is optional for /usr/sbin/nfs.idmap.  When the timeout
 is not specified, nfs.idmap will default to 600 seconds.
 
-id mapper uses for key descriptions:
+id mapper uses for key descriptions::
+
 	  uid:  Find the UID for the given user
 	  gid:  Find the GID for the given group
 	 user:  Find the user  name for the given UID
@@ -45,23 +47,24 @@ You can handle any of these individually, rather than using the generic upcall
 program.  If you would like to use your own program for a uid lookup then you
 would edit your request-key.conf so it look similar to this:
 
-#OP	TYPE	DESCRIPTION	CALLOUT INFO	PROGRAM ARG1 ARG2 ARG3 ...
-#======	=======	===============	===============	===============================
-create	id_resolver	uid:*	*		/some/other/program %k %d 600
-create	id_resolver	*	*		/usr/sbin/nfs.idmap %k %d 600
+``#OP	TYPE	DESCRIPTION	CALLOUT INFO	PROGRAM ARG1 ARG2 ARG3 ...``
+``#======	=======	===============	===============	===============================``
+``create	id_resolver	uid:*	*		/some/other/program %k %d 600``
+``create	id_resolver	*	*		/usr/sbin/nfs.idmap %k %d 600``
+
 
 Notice that the new line was added above the line for the generic program.
 request-key will find the first matching line and corresponding program.  In
 this case, /some/other/program will handle all uid lookups and
 /usr/sbin/nfs.idmap will handle gid, user, and group lookups.
 
-See <file:Documentation/security/keys/request-key.rst> for more information
+See Documentation/security/keys/request-key.rst for more information
 about the request-key function.
 
 
-=========
 nfs.idmap
 =========
+
 nfs.idmap is designed to be called by request-key, and should not be run "by
 hand".  This program takes two arguments, a serialized key and a key
 description.  The serialized key is first converted into a key_serial_t, and