Rexec
calls the
rexec(3)
routine to act as a client for the remote host's
rexecd(8)
server.
It asks that ``command'' be run on the host computer,
using username/password authentication. See
rexec(3)
and
rexecd(8)
for details of the protocol.
OPTIONS
Rexec
accepts several options, but only three are likely to be very useful:
-l username
Set the log-in name on the remote host to username.
-p password
Provide the password for the remote account. The command line argument
will be blanked after being parsed, to prevent it from being
seen with
ps(1).
However, it is still not very secure to type the password on the
command line. In particular, be sure that the shell's history file
is protected.
-n
Explicitly prompt for name and password, even if provided in
the environment, in the $HOME/.netrc file, or in the environmental
variables REXEC_USER and REXEC_PASS.
Other options that might be useful with non-standard remote exec
daemons, or to debug connections:
-a
Do not set up an auxiliary channel for standard error from command;
the remote standard error and output are then both returned on the
local standard output. By default,
rexec
asks that a separate channel be set up for diagnostic output
from the remote command.
-b
Use signal handling as in BSD rsh(1). Only the signals
SIGINT, SIGQUIT, and SIGTERM are echoed to the remote process.
They do not remain raised locally, so rexec waits for the
remote command to shutdown its side of the socket. Also, CNTRL-Z will
only suspend execution locally--the remote command may continue to run.
-c
Do not close remote standard input when local standard input closes.
Normally the standard input to the remote command is closed when
the local standard input is closed.
-d
Turn on debugging information. In particular the command sent to the
remote host will be echoed.
-h
Print a usage message.
-s
Do not echo signals received by the rexec onto the remote
process. Normally, signals which can be trapped are passed
on to the remote process; then, when you type CNTRL-C, the remote
process terminates as well.
USERNAME AND PASSWORD
Rexec(1)
searches for the username and password in the following order:
1. If -n is given on the command line, the user will always be
prompted for both, even if they are also given on the command line.
2. The command line will be parsed
3. If the environmental variables REXEC_USER or REXEC_PASS are
defined, they will define the username or password.
4. The $HOME/.netrc file will be searched. See
ftp(1)
for a description of this file's format.
5. Finally, the user will be prompted if either the username or password
remains undefined.
SECURITY
Users of this command should be aware that
rexec(3)
transmits their password to the remote host clear text, not
encrypted. If the network is not secure to the remote host, the
password can be comprimised.
SIGNALS
Without the -b option,
all signals which can be handled are echoed to the remote process.
Afterwards, however, they remain raised in the local process.
Typically, this means that
rexec(1)
will exit after receiving a fatal signal, even if the remote
process has arranged to handle or ignore it.
Differing operating systems use differing signal numbers; for example
AIX and SunOS use 18 for SIGTSTP (^Z), while Linux uses 20. Therefore,
it may have a different effect remotely than
locally. In particular, typing CNTL-Z may not suspend the execution
of the remote process.
