Hi

Finally, I found a workaround how to export a directory via NFS with two different shares, one with and one with no_root_squash:

First share: "home"
Path: /lvdss100/home/
[x] Use NFS
Allow access IP: 192.168.0.16/32;192.168.1.0/27
Allow write IP: 192.168.0.16/32;192.168.1.0/27
[ ] No root squash
Squash User: nobody
Squash Group: nogroup

Second share: "nrs"
Path: /lvdss100/ <- Here the "home" is missing.
[x] Use NFS
Allow access IP: 192.168.0.16/32 <- The backup host.
Allow write IP: 192.168.0.16/32
[x] No root squash

After mounting both shares,
dss1:/share/home on /dss/home1 type nfs (rw,acl,rsize=8192,wsize=8192,addr=192.168.4.1)
dss1:/share/nrs/home on /dss/nrs1 type nfs (rw,acl,rsize=8192,wsize=8192,addr=192.168.4.1)

everything works as expected:
fkt:/dss # touch /dss/home1/test_rw
touch: cannot touch `/dss/home1/test_rw': Permission denied
fkt:/dss # touch /dss/nrs1/test_rw

The only drawback is that the "nrs" share has to be mounted with the additional path fragment "home/", i.e. "dss1:/share/nrs/home" instead of "dss1:/share/nrs".

If someone has a more elegant solution (or can explain why the original straightforward attempt didn't work), please post. I will be able to check alternative concepts for the next days (before the servers go online again).

Best regards,
-mcr