PXE Boot fails: mount.nfs: Protocol not supported

[c.monty at web.de]

Hi,

I'm running FAI server in KVM.

Starting demohost (KVM, too) and booting PXE is generally working, but it fails in step "NFS mount".
The error message displayed in demohost is:
mount.nfs: Protocol not supported

This is the current NFS configuration on FAI server:
thomas at vm02-fai:~$ cat /etc/exports
# /etc/exports: the access control list for filesystems which may be exported
#               to NFS clients.  See exports(5).
#
# Example for NFSv2 and NFSv3:
# /srv/homes       hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
#
# Example for NFSv4:
# /srv/nfs4        gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
# /srv/nfs4/homes  gss/krb5i(rw,sync,no_subtree_check)
#
/srv/nfs4  192.168.33.0/24(fsid=0,async,ro,no_subtree_check)
/srv/fai/config 192.168.33.0/24(async,ro,no_subtree_check)
/srv/fai/nfsroot 192.168.33.0/24(async,ro,no_subtree_check,no_root_squash)


I can mount these NFS share on another client w/o problems:
thomas at vm01-debian9:~$ sudo mount -vv -t nfs 192.168.33.250:/srv/fai/nfsroot /mnt/
mount.nfs: timeout set for Fri Sep 15 12:03:10 2017
mount.nfs: trying text-based options 'vers=4.2,addr=192.168.33.250,clientaddr=192.168.33.11'
mount.nfs: mount(2): No such file or directory
mount.nfs: trying text-based options 'addr=192.168.33.250'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 192.168.33.250 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 192.168.33.250 prog 100005 vers 3 prot UDP port 52002

Checking mounts on this client reveals that NFS version 3 is used:
192.168.33.250:/srv/fai/nfsroot on /mnt type nfs (rw,relatime,vers=3,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.33.250,mountvers=3,mountport=52002,mountproto=udp,local_lock=none,addr=192.168.33.250)


What's causing the failure on demohost?

THX