Moo wrote:
>
> But when I rsh from 'linux machines that are in .rhosts to
> any of the Sun servers' it prompts for a password.

Give it the password and when you're logged in do "who am i".
Carefully note the hostname it says that you came in from.
Especially whether it uses the short name or FQDN. Whichever
name it gives, add that one to your .rhosts file and try again.

If it gives the IP number instead of either short hostname or
FQDN, then you have a DNS/DHCP automated update problem.
Your linux boxes aren't getting registered in DNS when they
get their DHCP leases.