rsh or remsh Command

Purpose

Executes the specified command at the remote host or logs into the remote host.

Syntax

{ rsh | remsh } RemoteHost [ -n ] [ -l User ] [ -f | -F ] [ -k realm] [ Command]

Description

The /usr/bin/rsh command executes the command specified by the Command parameter at the remote host specified by the RemoteHost parameter; if the Command parameter is not specified, the rsh command logs into the remote host specified by the RemoteHost parameter. The rsh command sends standard input from the local command line to the remote command and receives standard output and standard error from the remote command.

Note: Since any input to the remote command must be specified on the local command line, you cannot use the rsh command to execute an interactive command on a remote host. If you need to execute an interactive command on a remote host, use either the rlogin command or the rsh command without specifying the Command parameter. If you do not specify the Command parameter, the rsh command executes the rlogin command instead.

Access Files

If you do not specify the -l flag, the local user name is used at the remote host. If -l User is entered, the specified user name is used at the remote host.

Using Standard AIX Authentication

The remote host allows access only if at least one of the following conditions is satisfied:

• The local user ID is not the root user, and the name of the local host is listed as an equivalent host in the remote /etc/hosts.equiv file.
• If either the local user ID is the root user or the check of /etc/hosts.equiv is unsuccessful, the remote user's home directory must contain a $HOME/.rhosts file that lists the local host and user name.

Although you can set any permissions for the $HOME/.rhosts file, it is recommended that the permissions of the .rhosts file be set to 600 (read and write by owner only).

In addition to the preceding conditions, the rsh command also allows access to the remote host if the remote user account does not have a password defined. However, for security reasons, use of a password on all user accounts is recommended.

For Kerberos 5 Authentication

The remote host allows access only if all of the following conditions are satisfied:

• The local user has current DCE credentials.
• The local and remote systems are configured for Kerberos 5 authentication (On non-AIX remote systems, this may not be necessary. It is necessary that a daemon is listening to the klogin port).
• The remote system accepts the DCE credentials as sufficient for access to the remote account. See the kvalid_user function for additional information.

Remote Command Execution

While the remote command is executing, pressing the Interrupt, Terminate, or Quit key sequences sends the corresponding signal to the remote process. However, pressing the Stop key sequence stops only the local process. Normally, when the remote command terminates, the local rsh process terminates.

To have shell metacharacters interpreted on the remote host, place the metacharacters inside " " (double quotes). Otherwise, the metacharacters are interpreted by the local shell.

When using the rsh command, you can create a link to a path (to which you have permission to write), using a host name specified by the HostName parameter as the link name. For example:

ln -s /usr/bin/rsh HostName

Having established this link, you can specify the HostName parameter and a command specified by the Command parameter from the command line, and the rsh command remotely executes the command on the remote host. The syntax is:

HostName Command

For example, if you are linked to remote host opus and want to perform the date command, enter:

opus date

Because you can not specify the -l User flag, the remote command is successful only if the local user has a user account on the remote host. Otherwise, the rsh command returns a Login incorrect error message. When you specify the HostName parameter without a command, the rsh command calls the rlogin command, which logs you in to the remote host. Again, for successful login, the local user must have a user account on the remote host.

Flags

Examples

In the following examples, the local host, host1, is listed in the /etc/hosts.equiv file at the remote host, host2.

1. To check the amount of free disk space on a remote host, enter:

   rsh host2 df

   The amount of free disk space on host2 is displayed on the local system.
2. To append a remote file to another file on the remote host, place the >> metacharacters in quotation marks, and enter:

   rsh host2 cat test1 ">>" test2

   The file test1 is appended to test2 on remote host host2.
3. To append a remote file at the remote host to a local file, omit the quotation marks, and enter:

   rsh host2 cat test2 >> test3

   The remote file test2 on host2 is appended to the local file test3.
4. To append a remote file to a local file and use a remote user's permissions at the remote host, enter:

   rsh host2 -l jane cat test4 >> test5

   The remote file test4 is appended to the local file test5 at the remote host, with user jane's permissions.

Related Information

The ftp command, rcp command, rexec command, rlogin command, telnet, tn, or tn3270 command.

The rshd and krshd daemon.

The kvalid_user function.

The hosts.equiv file format, .rhosts file format.

Network Overview in AIX Version 4.3 System Management Guide: Communications and Networks.

Secure Rcmds in AIX Version 4.3 System User's Guide: Communications and Networks.