The tests are correct, I can reproduce it in s390x. Any v4.* mount fails, but v3 works:
root@nfs:~# mount localhost:/home /mnt/nfs_home -o vers=4.2 mount.nfs: mount system call failed for /mnt/nfs_home root@nfs:~# mount localhost:/home /mnt/nfs_home -o vers=4.1 mount.nfs: mount system call failed for /mnt/nfs_home root@nfs:~# mount localhost:/home /mnt/nfs_home -o vers=4.0 mount.nfs: mount system call failed for /mnt/nfs_home root@nfs:~# mount localhost:/home /mnt/nfs_home -o vers=4 mount.nfs: mount system call failed for /mnt/nfs_home root@nfs:~# mount localhost:/home /mnt/nfs_home -o vers=3 root@nfs:~# And no version at all also fails: root@nfs:~# mount localhost:/home /mnt/nfs_home mount.nfs: mount system call failed for /mnt/nfs_home dmesg is clean. Strace shows, for that last attempt with no version specified: 1998 mount("localhost:/home", "/mnt/nfs_home", "nfs", 0, "vers=4.2,addr=127.0.0.1,clientad"...) = -1 EIO (Input/output error) ** Summary changed: - DEP8 failures in noble/s390x + NFSv4 fails to mount in noble/s390x -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2060217 Title: NFSv4 fails to mount in noble/s390x To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nfs-utils/+bug/2060217/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs