Using RSH commands with REXECD

TCP/IP provides limited support for rsh, remsh, and similar commands. When such commands are issued against a VM host, a command to be executed on the remote VM host must be supplied. There is no support for the processing of interactive commands.

When an rsh command is received, it is processed by the VM REXECD server in essentially the same manner as an REXEC command. The same user ID and password verification mechanisms used for REXEC commands are used for rsh-supplied commands as well. An attempt is made to log on to the VM user ID that is identical to the local login id used to issue the rsh command; the value used is usually that which is maintained in the LOGNAME variable on Unix-based systems. The only exception to this is when a special password value of *guest has been provided.

Because VM requires a password to be supplied when logging on to a user, a password must be available. The rsh and remsh commands however have no inherent provision for doing so. Moreover, there is no rhosts (or similar) file maintained by the VM host for remote user authentication purposes. To bypass these limitations, the -l flag of the rsh command is used to provide the VM logon password as part of the rsh command. For example, when the following rsh command is issued from an AIX® system by the user wellsjr:

rsh gd3vm0 -l blues2me q cmslevel

the VM user ID WELLSJR will be logged on using the password BLUES2ME. The QUERY CMSLEVEL command is then executed on the host GD3VM0.

On other platforms, the rsh command may need to be specified using different flags. For example, from an OS/2 client, the above rsh command needs to be specified with both the -l and the -u flags:

rsh gd3vm0 -u welljr -l blues2me q cmslevel

If a user has no user ID on a remote VM system, rsh commands can still be issued, though in an anonymous manner. In this case, the supplied command will be processed by an REXEC agent virtual machine. To have an rsh command processed in this way, you need to specify a special value of *guest via the -l flag as shown below:

 rsh gd3vm0 -l *guest q cmslevel