Configure SSH between cluster nodes in Linux

Setting up SSH between the cluster nodes:

Setting up SSH on UNIX and Linux systems involves verifying that the SSH server daemon sshd is running and, if necessary, starting this daemon. Set up SSH on the DAS host and on all hosts where instances in your cluster will reside.
On UNIX and Linux systems, SSH software is typically installed as part of the base operating system. If SSH is not installed, download and install the appropriate OpenSSH SSH package for your operating system.


Each Node should be able to ssh to itself and each other.
If .ssh directory does not exist on the hosts create it.

cd ~  ( Make sure Oracle User Home is set to 750 – chmod 750 ~ )  (Very IMP..)
chmod -R og-rx .ssh ( or chmod 700)

On Node 1
1. cd ~/.ssh

2. Generate Public & Private RSA encryption Key pair
/usr/bin/ssh-keygen -t rsa
Enter file in which to save the key: /users/apps/dba/oracle/.ssh/id_rsa
Enter passphrase: No passphrase

3. Generate Public & Private DSA encryption Key pair
/usr/bin/ssh-keygen -t dsa
Enter file in which to save the key: /users/apps/dba/oracle/.ssh/id_dsa
Enter passphrase: No passphrase

4. cat ~ /.ssh/*.pub >> authorized_keys

5. scp the  authorized_keys to the subsequent Node under /users/apps/dba/oracle/.ssh

Repeat Step 1-5 on all Nodes. Once Step 4 is completed on the Last Node copy the authorized_keys from the Last Node to all other Nodes. This will replace the existing authorized_keys on the hosts with keys from the Last Node in the cluster.
Verify SSH

Make sure you have below soft-links for ssh/scp before you start the OUI Installer.
/usr/bin/ssh -> /opt/boksm/bin/ssh
/usr/bin/scp -> /opt/boksm/bin/scp
/usr/local/bin/ssh -> /opt/boksm/bin/scp
/usr/local/bin/scp -> /opt/boksm/bin/scp

Ssh as the oracle from each host in the cluster as below. If a password is prompted then ssh setup is done incorrectly.

ssh to both short primary host name and full primary host name.

From Host1: ssh Host1 date
From Host1: ssh Host2 date
From Host 2: ssh Host2 date
From Host 2: ssh Host1 date

Verify the above for all remaining hosts in the cluster.