From Newsgroup: comp.os.linux.networking

[Please advice if a better group exists for this question]

I have three PCs (1 each of Debian-12, Debian-13 and OpenSuse-15.6).
Each PC NFS-mounts a common directory from an NFS-Server (OpenSuse-15.6).

Mount options look the same on all three:

Opensuse:
xxx on xxx type nfs4 (rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.1.164,local_lock=none,addr=192.168.1.190)

Debian12
xxx on xxx type nfs4 (rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.1.168,local_lock=none,addr=192.168.1.190)

Debian13
xxx on xxx type nfs4 (rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.1.179,local_lock=none,addr=192.168.1.190)


When I try to 'flock' a file in a directory on that share simultaneously
on all 3 machines:
% flock foobar sh -c 'echo start ; sleep 10 ; echo end'

- when any Debian-machine holds the lock:
- the other two block as expected

- when the Opensuse machine holds the lock:
- the Debian-12 machine blocks as expected
- the Debian-13 machine fails with
% flock foobar sh -c 'echo start ; sleep 10 ; echo end'
flock: foobar: Input/output error

Any hint why the Debian-13 fails when Opensuse holds the lock?
Any hint where to start to look for answers?

TNX
R'
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