NFS v4 group mapping

[Aexoh5oo]

I am running Linux Mint 18.3 as an NFSv4 client. The client shows both user and group correctly but the group is wrong when writing or creating files.

The users' ids are defined locally in /etc/passwd and the groups in /etc/group. The users' ids are the same on both server and client, there being no number clash and I set them so. The users belong to group "staff" which has id 10 on the server and 50 on the client.

Viewing files works as expected, the group shows as staff/50 on the client and staff/10 on the server (ls -l, ls -n).

If I create a file with the client on the server I am shown group 4294967294/4294967294 by the client and gdm/50 is shown by the server.

Group gdm does not exist on the client as installed. If I create a group for gdm with id 99 then the created file shows as belonging to gdm/99 on the client and gdm/50 on the server. The files are created without translation with group 50 but are viewed back translated for gdm, 50 to 99.

Something is translating the group identity for reading but not writing, why?

[Aexoh5oo]

Hello,

No thoughts from forum users... I have circumvented the mapping problem by renumbering some of the client's groups. What problems this creates for the future is unknown, so far none, but I have read/write permissions on user files.