As Arvind noted you can log in to the OMS as "viouser" (with the password you set up during the installation) and SSH from there to other nodes on the control plane. The passwords on the other control plane nodes are randomly generated, but you can use preinstalled RSA keys to log in. In the /home/viouser/.ssh directory on the OMS you'll find a pre-generated public/private keypair. The public key has been preinstalled in the corresponding /home/viouser/.ssh/authorized_keys files on other other control plane nodes, so when you ssh to them from the OMS as "viouser" you won't need a password.
