the lustre2.1 doc say "The default group upcall is set by mkfs.lustre. Use tunefs.lustre --param or echo

>/proc/fs/lustre/mds/

/group_upcall" doesn't exist.

service150 /proc/fs/lustre/mds # ls -l /proc/fs/lustre/mds
total 0
rrr- 1 root root 0 Jan 11 12:23 num_refs

Also the line above this says "The default upcall is /usr/sbin/l_getidentity, which can interact with the user/group database to obtain UID/GID/suppgid. The user/group database depends on authentication configuration, and can be local /etc/passwd, NIS, LDAP, etc. If necessary, the administrator can use a parse utility to set /proc/fs/lustre/mdt/${FSNAME}-MDT

/identity_upcall. If the upcall interface is set to NONE, then upcall is disabled. The MDS uses the UID/GID/suppgid supplied by the client."

How do you setup group upcall?