User Commands rsh(1)
NAME
rsh, remsh, remoteshell - remote shell
SYNOPSIS
rsh [-n] [-a] [-K] [-PN -PO] [-x] [-f -F] [-l username]
[-k realm] hostname command
rsh hostname [-n] [-a] [-K] [-PN -PO] [-x] [-f -F]
[-l username] [-k realm] command
remsh [-n] [-a] [-K] [-PN -PO] [-x] [-f -F] [-l username]
[-k realm] hostname command
remsh hostname [-n] [-a] [-K] [-PN -PO] [-x] [-f -F]
[-l username] [-k realm] command
hostname [-n] [-a] [-PN -PO] [-x] [-f -F]
[-l username] [-k realm] command
DESCRIPTION
The rsh utility connects to the specified hostname and exe-
cutes the specified command. rsh copies its standard input
to the remote command, the standard output of the remote
command to its standard output, and the standard error of
the remote command to its standard error. Interrupt, quit,
and terminate signals are propagated to the remote command.
rsh normally terminates when the remote command does.
The user can opt for a secure session of rsh which uses Ker-
beros V5 for authentication. Encryption of the network ses-
sion traffic is also possible. The rsh session can be ker-
berized using any of the following Kerberos specific
options: -a, -PN or -PO, -x, -f or -F, and -k realm. Some of
these options (-a, -x, -PN or -PO, and -f or -F) can also be
specified in the [appdefaults] section of krb5.conf(4). The
usage of these options and the expected behavior is dis-
cussed in the OPTIONS section below. If Kerberos authentica-
tion is used, authorization to the account is controlled by
rules in krb5authrules(5). If this authorization fails,
fallback to normal rsh using rhosts occurs only if the -PO
option is used explicitly on the command line or is speci-
fied in krb5.conf(4). Also, the -PN or -PO, -x, -f or -F,
and -k realm options are just supersets of the -a option.
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User Commands rsh(1)
If you omit command, instead of executing a single command,
rsh logs you in on the remote host using rlogin(1).
rsh does not return the exit status code of command.
Shell metacharacters which are not quoted are interpreted on
the local machine, while quoted metacharacters are inter-
preted on the remote machine. See EXAMPLES.
If there is no locale setting in the initialization file of
the login shell (.cshrc, . . .) for a particular user, rsh
always executes the command in the "C" locale instead of
using the default locale of the remote machine.
The command is sent unencrypted to the remote system. All
subsequent network session traffic is encrypted. See -x.
OPTIONS
The following options are supported:
-a Explicitly enable Kerberos authentication and
trusts the .k5login file for access-control.
If the authorization check by in.rshd(1M) on
the server-side succeeds and if the .k5login
file permits access, the user is allowed to
carry out the command.
-f Forward a copy of the local credentials (Ker-
beros Ticket Granting Ticket) to the remote
system. This is a non-forwardable ticket
granting ticket. Forward a ticket granting
ticket if you need to authenticate yourself
to other Kerberized network services on the
remote host. An example would be if your home
directory on the remote host is NFS mounted
by way of Kerberos V5. If your local creden-
tials are not forwarded in this case, you
cannot access your home directory. This
option is mutually exclusive with the -F
option.
-F Forward a forwardable copy of the local
credentials (Kerberos Ticket Granting Ticket)
to the remote system. The -F option provides
a superset of the functionality offered by
the -f option. For example, with the -f
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option, if, after you connected to the remote
host, your remote command attempted to invoke
/usr/bin/ftp, /usr/bin/telnet,
/usr/bin/rlogin, or /usr/bin/rsh, with the -f
or -F options, the attempt would fail. Thus,
you would be unable to push your single net-
work sign on trust beyond one system. This
option is mutually exclusive with the -f
option.
-k realm Causes rsh to obtain tickets for the remote
host in realm instead of the remote host's
realm as determined by krb5.conf(4).
-K This option explicitly disables Kerberos
authentication. It can be used to override
the autologin variable in krb5.conf(4).
-l username Uses username as the remote username instead
of your local username. In the absence of
this option, the remote username is the same
as your local username.
-n Redirect the input of rsh to /dev/null. You
sometimes need this option to avoid unfor-
tunate interactions between rsh and the shell
which invokes it. For example, if you are
running rsh and invoke a rsh in the back-
ground without redirecting its input away
from the terminal, it blocks even if no reads
are posted by the remote command. The -n
option prevents this.
-PO Explicitly request new (-PN) or old (-PO)
-PN version of the Kerberos "rcmd" protocol. The
new protocol avoids many security problems
prevalant in the old one and is regarded much
more secure, but is not interoperable with
older (MIT/SEAM) servers. The new protocol is
used by default, unless explicitly specified
using these options or through krb5.conf(4).
If Kerberos authorization fails when using
the old "rcmd" protocol, there is fallback to
regular, non-kerberized rsh. This is not the
case when the new, more secure "rcmd" proto-
col is used.
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User Commands rsh(1)
-x Cause the network session traffic to be
encrypted. See DESCRIPTION.
The type of remote shell (sh, rsh, or other) is determined
by the user's entry in the file /etc/passwd on the remote
system.
OPERANDS
The following operand is supported:
command The command to be executed on the specified host-
name.
USAGE
See largefile(5) for the description of the behavior of rsh
and remsh when encountering files greater than or equal to 2
Gbyte ( 2^31 bytes).
The rsh and remsh commands are IPv6-enabled. See ip6(7P).
IPv6 is not currently supported with Kerberos V5 authentica-
tion.
Hostnames are given in the hosts database, which can be con-
tained in the /etc/hosts file, the Internet domain name
database, or both. Each host has one official name (the
first name in the database entry) and optionally one or more
nicknames. Official hostnames or nicknames can be given as
hostname.
If the name of the file from which rsh is executed is any-
thing other than rsh, rsh takes this name as its hostname
argument. This allows you to create a symbolic link to rsh
in the name of a host which, when executed, invokes a remote
shell on that host. By creating a directory and populating
it with symbolic links in the names of commonly used hosts,
then including the directory in your shell's search path,
you can run rsh by typing hostname to your shell.
If rsh is invoked with the basename remsh, rsh checks for
the existence of the file /usr/bin/remsh. If this file
exists, rsh behaves as if remsh is an alias for rsh. If
/usr/bin/remsh does not exist, rsh behaves as if remsh is a
host name.
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For the kerberized rsh session, each user can have a private
authorization list in a file .k5login in their home direc-
tory. Each line in this file should contain a Kerberos prin-
cipal name of the form principal/instance@realm. If there is
a ~/.k5login file, then access is granted to the account if
and only if the originater user is authenticated to one of
the principals named in the ~/.k5login file. Otherwise, the
originating user is granted access to the account if and
only if the authenticated principal name of the user can be
mapped to the local account name using the authenticated-
principal-name -> local-user-name mapping rules. The
.k5login file (for access control) comes into play only when
Kerberos authentication is being done.
For the non-secure rsh session, each remote machine can have
a file named /etc/hosts.equiv containing a list of trusted
hostnames with which it shares usernames. Users with the
same username on both the local and remote machine can run
rsh from the machines listed in the remote machine's
/etc/hosts.equiv file. Individual users can set up a similar
private equivalence list with the file .rhosts in their home
directories. Each line in this file contains two names: a
hostname and a username separated by a space. The entry per-
mits the user named username who is logged into hostname to
use rsh to access the remote machine as the remote user. If
the name of the local host is not found in the
/etc/hosts.equiv file on the remote machine, and the local
username and hostname are not found in the remote user's
.rhosts file, then the access is denied. The hostnames
listed in the /etc/hosts.equiv and .rhosts files must be the
official hostnames listed in the hosts database; nicknames
can not be used in either of these files.
You cannot log in using rsh as a trusted user from a trusted
hostname if the trusted user account is locked.
rsh does not prompt for a password if access is denied on
the remote machine unless the command argument is omitted.
EXAMPLES
Example 1 Using rsh to Append Files
The following command appends the remote file lizard.file
from the machine called lizard to the file called
example.file on the machine called example:
example% rsh lizard cat lizard.file >> example.file
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The following command appends the file lizard.file on the
machine called lizard to the file lizard.file2 which also
resides on the machine called lizard:
example% rsh lizard cat lizard.file ">>" lizard.file2
EXIT STATUS
The following exit values are returned:
0 Successful completion.
1 An error occurred.
FILES
/etc/hosts Internet host table
/etc/hosts.equiv Trusted remote hosts and users
/etc/passwd System password file
$HOME/.k5login File containing Kerberos principals
that are allowed access
/etc/krb5/krb5.conf Kerberos configuration file
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
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ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWrcmdc
CSI Enabled
SEE ALSO
on(1), rlogin(1), ssh(1), telnet(1), vi(1), in.rshd(1M),
hosts(4), hosts.equiv(4), krb5.conf(4), attributes(5),
krb5authrules(5), largefile(5), ip6(7P)
NOTES
When a system is listed in hosts.equiv, its security must be
as good as local security. One insecure system listed in
hosts.equiv can compromise the security of the entire sys-
tem.
You cannot run an interactive command (such as vi(1)). Use
rlogin if you wish to do this.
Stop signals stop the local rsh process only. This is argu-
ably wrong, but currently hard to fix for reasons too com-
plicated to explain here.
The current local environment is not passed to the remote
shell.
Sometimes the -n option is needed for reasons that are less
than obvious. For example, the command:
example% rsh somehost dd if=/dev/nrmt0 bs=20b tar xvpBf -
puts your shell into a strange state. Evidently, the tar
process terminates before the rsh process. The rsh command
then tries to write into the ``broken pipe'' and, instead of
terminating neatly, proceeds to compete with your shell for
its standard input. Invoking rsh with the -n option avoids
such incidents.
This bug occurs only when rsh is at the beginning of a pipe-
line and is not reading standard input. Do not use the -n
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User Commands rsh(1)
option if rsh actually needs to read standard input. For
example:
example% tar cf - . rsh sundial dd of=/dev/rmt0 obs=20b
does not produce the bug. If you were to use the -n option
in a case like this, rsh would incorrectly read from
/dev/null instead of from the pipe.
For most purposes, ssh(1) is preferred over rsh.
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