School of Computing
and Communications
D35 InfoLab21
Lancaster University
Lancaster, LA1 4WA
United Kingdom
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nfsidmap
Section: File Formats (5)Updated: 1 October 2010
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NAME
nfsidmap - The NFS idmapper upcall programDESCRIPTION
The file /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. /usr/sbin/nfsidmap should only be called by request-key, and will perform the translation and initialize a key with the resulting information.NFS_USE_NEW_IDMAPPER must be selected when configuring the kernel to use this feature.
CONFIGURING
The file /etc/request-key.conf will need to be modified so /sbin/request-key can properly direct the upcall. The following line should be added before a call to keyctl negate:
create id_resolver * * /usr/sbin/nfsidmap %k %d 600
This will direct all id_resolver requests to the program /usr/sbin/nfsidmap The last parameter, 600, defines how many seconds into the future the key will expire. This is an optional parameter for /usr/sbin/nfsidmap and will default to 600 seconds when not specified.
The idmapper system uses four 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
group: Find the group name for the given GID
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:
create id_resolver uid:* * /some/other/program %k %d 600
create id_resolver * * /usr/sbin/nfsidmap %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 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.
AUTHOR
Bryan Schumaker, <bjschuma@netapp.com>
Index
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