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Setting up ssh on cluster systems

Use the Secure Shell (ssh) to install VCS on all systems in a cluster from a system outside of the cluster. Verify that ssh is configured correctly before starting the installation process.

Secure Shell (ssh) is a program to log on to another computer over a network, to execute commands on a remote system, and to copy files from one system to another. The ssh provides strong authentication and secure communications over channels. It is intended to replace rlogin, rsh, and rcp.

The Remote Shell (rsh) is disabled by default to provide better security. Use ssh for remote command execution.

Configuring ssh

The procedure to configure ssh uses OpenSSH example file names and commands.

 To configure ssh

1. Log on to the system from which you want to install VCS.
2. Generate a DSA key pair on this system by running the following command:

   # ssh-keygen -t dsa

3. Accept the default location of ~/.ssh/id_dsa.
4. When prompted, enter a passphrase and confirm it.
5. Change the permissions of the .ssh directory by typing:

   # chmod 755 ~/.ssh

6. The file ~/.ssh/id_dsa.pub contains a line beginning with ssh_dss and ending with the name of the system on which it was created. Copy this line to the /root/.ssh/authorized_keys2 file on all systems where VCS is to be installed.

   If the local system is part of the cluster, make sure to edit the authorized_keys2 file on that system.

7. Run the following commands on the system from which the installation is taking place:

   # exec /usr/bin/ssh-agent $SHELL

   # ssh-add

   This step is shell-specific and is valid for the duration the shell is alive.

8. When prompted, enter your DSA passphrase.

   You are ready to install VCS on several systems by running the installvcs program on any one of them or on an independent system outside the cluster.

   To avoid running the ssh-agent on each shell, run the X-Window system and configure it so that you will not be prompted for the passphrase. Refer to the Red Hat documentation for more information.

9. To verify that you can connect to the systems on which VCS is to be installed, type:

   # ssh -x -l root north ls

   # ssh -x -l root south ifconfig

The commands should execute on the remote system without having to enter a passphrase or password.

  Note   You can configure ssh in other ways. Regardless of how ssh is configured, complete the last step in the example above to verify the configuration.