rmt-0.4b21-3 is using a non-compatible version of the protocol and causes the Sun to blow up (nova?). Here's the output from ufsdump: DUMP: rmtstatus: expected response size 24, got 28 DUMP: This means the remote rmt daemon is not compatible. DUMP: Lost connection to remote host. DUMP: Bad return code from dump: 1 Should I just give up and put the tape on a Solaris machine?
Received a reply from the maintainer of dump. It's a known bug, and he can't fix it -- someone with access to Solaris source will have to.