I upgraded my home server from Debian 8 to 9 and afterwards could not mount NFS shares from my Synology Diskstation (running DSM 4.2) anymore:
$ journalctl -x systemd[1]: mnt-media\x2ddisa.mount: Mount process exited, code=exited status=32 systemd[1]: Failed to mount /mnt/media-disa. -- Subject: Unit mnt-media\x2ddisa.mount has failed -- Defined-By: systemd -- Support: https://www.debian.org/support -- -- Unit mnt-media\x2ddisa.mount has failed. -- -- The result is failed. kernel: NFS: nfs4_discover_server_trunking unhandled error -22. Exiting with error EIO systemd[1]: Dependency failed for Remote File Systems. -- Subject: Unit remote-fs.target has failed -- Defined-By: systemd -- Support: https://www.debian.org/support -- -- Unit remote-fs.target has failed. -- -- The result is dependency. systemd[1]: remote-fs.target: Job remote-fs.target/start failed with result 'dependency'. systemd[1]: mnt-media\x2ddisa.mount: Unit entered failed state.
I found a Fedora bug report that suggested to specify the NFS version that should be used for mounting.
So I edited /etc/fstab and added nfsvers=4 to the mount options, and mounting works since.
/etc/fstab
disa:/volume2/data /mnt/data-disa nfs user,nolock,nfsvers=4