In my place, we use Red Hat Enterprise Linux 5 (RHEL5) for the cluster nodes. In order for the application to run, we need to enable passwordless logins via rsh, in order for the Message Passing Interface & Node Management Software to work. There are a few ways to do this, this is how I did it. Security Professionals will be screaming though.

1. Firstly, make sure you have installed the rsh-server rpm package.

   [root@node01 ~]# yum install rsh-server
   Loaded plugins: rhnplugin, security
   This system is not registered with RHN.
   RHN support will be disabled.
   Setting up Install Process
   Parsing package install arguments
   Resolving Dependencies
   --> Running transaction check
   ---> Package rsh-server.i386 0:0.17-38.el5 set to be updated
   --> Finished Dependency Resolution
    
   Dependencies Resolved
    
   ================================================================================
    Package           Arch        Version               Repository            Size
   ================================================================================
   Installing:
    rsh-server        i386        0.17-38.el5           rhel-selrepos         39 k
    
   Transaction Summary
   ================================================================================
   Install      1 Package(s)
   Update       0 Package(s)
   Remove       0 Package(s)
    
   Total download size: 39 k
   Is this ok [y/N]: y
   Downloading Packages:
   Running rpm_check_debug
   Running Transaction Test
   Finished Transaction Test
   Transaction Test Succeeded
   Running Transaction
     Installing     : rsh-server                                        [1/1]
    
   Installed: rsh-server.i386 0:0.17-38.el5
   Complete!

2. Make sure the rsh, rlogin, rexec, xinetd are turned on and then restart xinetd.

   [root@node01 ~]# chkconfig rsh on
   [root@node01 ~]# chkconfig rexec on
   [root@node01 ~]# chkconfig rlogin on
   [root@node01 ~]# chkconfig xinetd on
   [root@node01 ~]# service xinetd restart
   Stopping xinetd:                                           [  OK  ]
   Starting xinetd:                                           [  OK  ]

3. Edit your /etc/securetty file. Append the following

   rsh
   rexec
   rlogin

4. You’ll then need to create a .rhosts file in the user’s home directory, with the host names of the machines you wish to allow to connect.
   Note:These machines should be resolvable via either DNS or put in your /etc/hosts file.

   node01
   node02
   node03

   Also, make sure the file permissions are 0600.

   chmod 0600 ~/.rhosts

You should be able to rsh in now.