I'm running NetBSD-1.2(beta) on a Sparc 5.  I'm trying to set it
   up as an NFS server.  I'm doing all of this by hand after the machine has
   been up, if that matters.  I have an /etc/exports that looks like:

   /export/sun4-netbsd1 -ro all_ng

You didn't explain the meaning of "all_ng" but I presume you intended
to create a netgroup in /etc/netgroup by that name.  If this is so,
you need to recreate the netgroup databases using netgroup_mkdb before
this will work.

Hope that helps.

Cheers,
Brook