The author encountered a problem.
I added a user A to the two groups B and C, and then accessed the directory with the permissions of the directory group B and C, and it appeared Permission denied, but obviously the user was in these two groups.
After analyzing and reappearing the problem, it is found that before adding user A to groups B and C, the user has already joined 16 groups. Due to the limitation of nas mount, a user can join up to 16 groups.
Reason: The RPC message of the NFS protocol has a maximum of 16 group messages, and the excess part will be discarded. Therefore, the RPC message received by the protocol layer on the storage side will not contain group17 information, resulting in authentication failure. .
If there is no nas mount limit, how many groups a user can join, the answer is 32.