============== How to Configure SSH for a RAC Installation ==============

This document will explain how to configure SSH, which is required to run a RAC installation. Following the instructions in the installation guide are also correct, but sometimes this will not work, although the reason for that isn't clear. Therefore, after some investigation it seems to be that the steps below will work too.

Starting with 11gR2 the Oracle Universal Installer the SSH can be setup automatically using the ’SSH Connectivity' button.

In this article, we will show you how to set up password-less login on RHEL-based Linux distributions

Step 1

To configure SSH you need to perform the following steps on each node in the cluster.

$ cd $HOME
$ mkdir .ssh
$ chmod 700 .ssh
$ cd .ssh
$ ssh-keygen -t rsa

Now accept the default location for the key file
Enter and confirm a passphrase. (you can also press enter twice).

$ ssh-keygen -t dsa

At the prompts, accept the default location for the key file (press Enter).
Then press "Enter" twice to accept no passphrase.

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Please note: SSH with passphrase is not supported for Oracle Clusterware 11g release 2 and later releases.

If you provide a passphrase for pre 11.2 release, then you need to do 2 addition steps.

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

These statements will inform the ssh agent to add the keys to the shell used .

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Step 2

$ cat *.pub >> authorized_keys.<nodeX> (nodeX could be the nodename to differentiate files later)

Now do the same steps on the other nodes in the cluster.When all those steps are done on the other nodes, start to copy the authorized_keys.<nodeX> to all the nodes into $HOME/.ssh/

For example if you have 4 nodes you will have after the copy in the .ssh 4 files with the name authorized_keys.<nodeX>

Step 3

Then on EACH node continue the configuration of SSH by doing the following:

$ cd $HOME/.ssh
$ cat *.node* >> authorized_keys
$ chmod 600 authorized_keys

NOTE: ALL public keys must appear in ALL authorized_keys files, INCLUDING the LOCAL public key for each node.

To test that everything is working correct now execute the commands

$ ssh <hostnameX> date

Thank you to All ....

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