--- /dev/null
+.\"
+.\"@(#)nfsidmap(8) - The NFS idmapper upcall program
+.\"
+.\" Copyright (C) 2010 Bryan Schumaker <bjschuma@netapp.com>
+.TH nfsidmap 5 "1 October 2010"
+.SH NAME
+nfsidmap \- The NFS idmapper upcall program
+.SH DESCRIPTION
+The file
+.I /usr/sbin/nfsidmap
+is used by the NFS idmapper to translate user and group ids into names, and to
+translate user and group names into ids. Idmapper uses request-key to perform
+the upcall and cache the result.
+.I /usr/sbin/nfsidmap
+should only be called by request-key, and will perform the translation and
+initialize a key with the resulting information.
+.PP
+NFS_USE_NEW_IDMAPPER must be selected when configuring the kernel to use this
+feature.
+.SH CONFIGURING
+The file
+.I /etc/request-key.conf
+will need to be modified so
+.I /sbin/request-key
+can properly direct the upcall. The following line should be added before a call
+to keyctl negate:
+.PP
+create nfs_idmap * * /usr/sbin/nfsidmap %k %d 600
+.PP
+This will direct all nfs_idmap requests to the program
+.I /usr/sbin/nfsidmap
+The last parameter, 600, defines how many seconds into the future the key will
+expire. This is an optional parameter for
+.I /usr/sbin/nfsidmap
+and will default to 600 seconds when not specified.
+.PP
+The idmapper system uses four key descriptions:
+.PP
+ uid: Find the UID for the given user
+.br
+ gid: Find the GID for the given group
+.br
+ user: Find the user name for the given UID
+.br
+ group: Find the group name for the given GID
+.PP
+You can choose to 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 looks similar to this:
+.PP
+create nfs_idmap uid:* * /some/other/program %k %d 600
+.br
+create nfs_idmap * * /usr/sbin/nfsidmap %k %d 600
+.PP
+Notice that the new line was added above the line for the generic program.
+request-key will find the first matching line and run the corresponding program.
+In this case, /some/other/program will handle all uid lookups, and
+/usr/sbin/nfsidmap will handle gid, user, and group lookups.
+.SH AUTHOR
+Bryan Schumaker, <bjschuma@netapp.com>