You can do it, it just isn't really documented at all.. Sun just tells you to run the scripts on the disks (setup_install_server, add_install_client), which modify a whole bunch of system files to setup netbooting. You can do things manually though, it involves the same kinds of things that you would do to netboot something like debian:
- dhcp ( though lots of guides have you use rarpd, not sure why as newer boxes do dhcp)
If you read those two scripts you can sort of figure out what needs to be done..
You just need to copy the files to the right places on the hard drive, and setup rarpd+tftp+nfs.
This guide talks about solaris 10:
and according to them you can at least run setup_install_server in linux these days.
FYI, you can get solaris 10 and opensolaris as cdrom images..