How to setup SSH passwordless root login
Environment
UCS 4.4 and UCS 5
Preparation
Step 1: Check for existing SSH key pair
Check if a key is already existing:
ls -al ~/.ssh/id_*.pub
If there is an existing key you can try to use that one. Jump to Step 3.
Step 2: Generate a new SSH key pair
ssh-keygen -t rsa -b 4096
If you have found an existing key, use a different name. If not you can use the default one or you name it like you want. Do not enter a passphrase.
Activate passwordless login on the servers
ssh-copy-id -i .ssh/<PUBLIC-keyname> root@server_ip_address
Ensure you use the public key name! If you have name the id_rsa, the public one is named id_rsa.pub!
You need to enter the root password on the external server to transfer the key
Verify the passwordless login
ssh remote_username@server_ip_address
You should get connected without password. If you used an existing key and you are asked for the passphrase of the key, you need to start over an generate one without a passphrase.
Remove the passwordless login again
If you want to deactivate the passwordless login on a server, you need to remove the line that contains the public key of the host you want to remove the login from.
Get public key on the server you want to remove the passwordless access from do
cat .ssh/id_rsa.pub
on that host and go to the server you want to remove the access to and
vi .ssh/authorized_keys
search the line that contains the key; in the end of every line the remote host is named it could help to search the hostname of the host you want to remove the passwordless access from