+.I nfsidmap
+can also used to clear the keyring of all the keys or
+revoke one particular key.
+This is useful when the id mappings have failed to due
+to a lookup error resulting in all the cached uids/gids to be set
+to the user id nobody.
+.SH OPTIONS
+.TP
+.B -c
+Clear the keyring of all the keys.
+.TP
+.B -g user
+Revoke the gid key of the given user.
+.TP
+.B -r user
+Revoke both the uid and gid key of the given user.
+.TP
+.B -t timeout
+Set the expiration timer, in seconds, on the key.
+The default is 600 seconds (10 mins).
+.TP
+.B -u user
+Revoke the uid key of the given user.
+.TP
+.B -v
+Increases the verbosity of the output to syslog
+(can be specified multiple times).