A/UX: Remote Dump to Magnetic Tape Drive

I'm trying to do a remote dump (rdump) from a Macintosh IIfx on an Ethernet
network to a 1/4-inch cassette tape drive on a Concurrent computer on the
same network. The device file for the tape drive is /dev/rctp. The
address on the network and in the /etc/NETHOSTS is mdsaero. I think
everything is set up properly now since the dump process begins. The
following is the command I issued:

macunix.root 1 # rdump 0usf 28800 mdsaero:/dev/rctp /dev/dsk/c5d0s3
DUMP: Date of this level 0 dump: Mon Feb 24 15:33:14 1992
DUMP: Date of last level 0 dump: the epoch
DUMP: Dumping /dev/rdsk/c5d0s3 (/users) to /dev/rctp on host mdsaero
DUMP: mapping (Pass I) [regular files]
DUMP: mapping (Pass II) [directories]
DUMP: estimated 201945 blocks on 0.41 tape(s).
DUMP: Protocol to remote tape server botched (code /etc/rmt: Command not
found.
?).
rdump: Lost connection to remote host.
DUMP: Bad return code from dump: 1
macunix.root 2 #

Note: slice 3 is a 400MB (approximately) partition and the tape cassette is
a 525MB tape. The procedure also won't work with a 120MB tape.

According to the above error message, "... remote tape server botched (code
/etc/rmt: Command not found," the problem is apparently on the remote host.

The /etc/rmt can't be found in the mdsaero host. The /etc/rmt is a remote
magtape protocol program used by the remote dump (rdump) and remote restore
(rrestore) programs in manipulating a magnetic tape drive through an IPC
(Inter Process Communication) connection. The /etc/rmt is normally started
up with an rexec() and rcmd() call.

Check the mdsaero host to see if it supports the remote procedure call for
a remote magnetic tape drive. A/UX and most BSD UNIX systems support this
facility.