> is there a way, to set up an fai-config-server with nfsroot on an > x86-based server, if the target-architecture is x64?
Depends on your definition of 'set up'. You can install X86_64 clients from a X86_32 server. You cannot create a 64bit nfsroot on a 32bit host. You definitely need some 64bit machine where to do the initial configuration and create a 64bit nfsroot. After it's been created you can move the nfsroot and the config space to a different machine. You can even use a SPARC/Solaris environment to host the nfsroot and the config space. (It's just NFS and DHCP anyway.) However you can't simply chroot into your nfsroot and modify/update it.