I have a problem I'm hoping someone can help me with...

I have an NFS server/client setup. On the server side, I export a romfs filesystem to the NFS. The client computers boot via PXE bootloader and mount their root filesystem via NFS, using tempfs/unionfs to make parts of the filesystem read/write (i.e., /etc, /var, etc)

The OS itself is based on Linux From Scratch, so the kernel sources are straight from kernel.org. As far as I can tell, the NFS and network filesystem options in both kernels is correct.

I had been using kernel 2.6.26.5 without issue. However recently I've been trying to upgrade to kernel 2.6.31.5. Now when I try to export the romfs filesystem via NFS I get this error message...

exportfs: Warning: /diskless does not support NFS export

I can export an ext3 filesystem via NFS... it seems that the newer kernel doesn't like romfs. I've been through the changelogs between 2.6.26.5 and 2.6.31.5 and didn't see anything that jumped out at me.

Has anyone managed to successfully export a romfs to NFS using a bleeding-edge kernel? Does anyone know what I could be doing wrong?