Network File System - Wikipedia
https://en.wikipedia.org/wiki/Network_File_SystemNetwork File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun) in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. NFS is an open IETF standard defined in a Request for Comments (RFC), allowing anyone to implement the protocol.
linux - NFS user mapping - Server Fault
https://serverfault.com/questions/520276V4 relay on the fact, that user names are shared between client and server, while uid/gid cant be different. In opposite, v3 shares uid and gid. Probably, you have to mount with vers=3 to solve your problem. The other possibility to turn off id mapping on the server side: echo "options nfs nfs4_disable_idmapping=1" > /etc/modprobe.d/nfs.conf