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rsh

BSD mandoc
HEIMDAL

NAME

rsh - remote shell

SYNOPSIS

[-45FGKdefnuxz ] [-U string ] [-p port ] [-l username ] [-P N|O ] host [command]

DESCRIPTION

authenticates to the rshd(8) daemon on the remote host and then executes the specified command

copies its standard input to the remote command, and the standard output and error of the remote command to its own.

Valid options are:

-4 --krb4

The -4 option requests Kerberos 4 authentication. Normally all supported authentication mechanisms will be tried, but in some cases more explicit control is desired.

-5 --krb5

The -5 option requests Kerberos 5 authentication. This is analogous to the -4 option.

-K --broken

The -K option turns off all Kerberos authentication. The security in this mode relies on reserved ports. The long name is an indication of how good this is.

-n --no-input

The -n option directs the input from the /dev/null device (see the Sx BUGS section of this manual page).

-d

Enable setsockopt(2) socket debugging.

-e --no-stderr

Don't use a separate socket for the stderr stream. This can be necessary if rsh-ing through a NAT bridge.

-x --encrypt

The -x option enables encryption for all data exchange. This is only valid for Kerberos authenticated connections (see the Sx BUGS section for limitations).

-z

The opposite of -x This is the default, and is mainly useful if encryption has been enabled by default, for instance in the appdefaults section of /etc/krb5.conf when using Kerberos 5.

-f --forward

Forward Kerberos 5 credentials to the remote host. Also settable via appdefaults (see krb5.conf).

-F --forwardable

Make the forwarded credentials re-forwardable. Also settable via appdefaults (see krb5.conf).

-l string --user= string

By default the remote username is the same as the local. The -l option or the username@host format allow the remote name to be specified.

-n --no-input

Direct input from /dev/null (see the Sx BUGS section).

-p number-or-service --port= number-or-service

Connect to this port instead of the default (which is 514 when using old port based authentication, 544 for Kerberos 5 and non-encrypted Kerberos 4, and 545 for encrytpted Kerberos 4; subject of course to the contents of /etc/services )

-P N|O|1|2 --protocol= N|O|1|2

Specifies the protocol version to use with Kerberos 5. N and 2 select protocol version 2, while O and 1 select version 1. Version 2 is believed to be more secure, and is the default. Unless asked for a specific version, will try both. This behaviour may change in the future.

-u --unique

Make sure the remote credentials cache is unique, that is, don't reuse any existing cache. Mutually exclusive to -U

-U string --tkfile= string

Name of the remote credentials cache. Mutually exclusive to -u

-x --encrypt

The -x option enables encryption for all data exchange. This is only valid for Kerberos authenticated connections (see the Sx BUGS section for limitations).

-z

The opposite of -x This is the default, but encryption can be enabled when using Kerberos 5, by setting the libdefaults/encrypt option in krb5.conf5.

EXAMPLES

Care should be taken when issuing commands containing shell meta characters. Without quoting, these will be expanded on the local machine.

The following command:

rsh otherhost cat remotefile > localfile

will write the contents of the remote remotefile to the local localfile but:

rsh otherhost 'cat remotefile > remotefile2'

will write it to the remote remotefile2

FILES

/etc/hosts

SEE ALSO

rlogin(1), krb_realmofhost3, krb_sendauth3, hosts.equiv5, krb5.conf5, rhosts(5), kerberos(8) rshd(8)

HISTORY

The command appeared in BSD 4.2

AUTHORS

This implementation of was written as part of the Heimdal Kerberos 5 implementation.

BUGS

Some shells (notably csh(1)) will cause to block if run in the background, unless the standard input is directed away from the terminal. This is what the -n option is for.

The -x options enables encryption for the session, but for both Kerberos 4 and 5 the actual command is sent unencrypted, so you should not send any secret information in the command line (which is probably a bad idea anyway, since the command line can usually be read with tools like ps(1)). Forthermore in Kerberos 4 the command is not even integrity protected, so anyone with the right tools can modify the command.