We have now confirmed that the problem is the NFS mounts in /etc/fstab.
Setting the NFS entries in fstab to "noauto" completely removes the problem:
There is no timeout during boot, and no lockup any more. The machine boote smoothly with the NFS-shares unmounted. After the machine is up, we can manually mount the NFS-shares without a problem.
This is definitely a race condition during bootup:
the NFS shares seem to be mounted at a time, where the network is not yet up, and waiting for the network to come up locks up the boot process.
We have now confirmed that the problem is the NFS mounts in /etc/fstab.
Setting the NFS entries in fstab to "noauto" completely removes the problem:
There is no timeout during boot, and no lockup any more. The machine boote smoothly with the NFS-shares unmounted. After the machine is up, we can manually mount the NFS-shares without a problem.
This is definitely a race condition during bootup:
the NFS shares seem to be mounted at a time, where the network is not yet up, and waiting for the network to come up locks up the boot process.