3 Steps to Perform SSH Login Without Password Using ssh-keygen & ssh-copy-id

ssh-keygen creates public and private keys. ssh-copy-id copies the local host's public key to the remote host's authorized_keys file. ssh-copy-id also assigns proper permission to the remote host's home, ~/.ssh, and ~/.ssh/authorized_keys.

                                          

Step 1: Create public and private keys using ssh-keygen on local-host

root@local-host$ [Note: You are on local-host here]

root@local-host$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/root/.ssh/id_rsa):[Enter key]
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Pess enter key]
Your identification has been saved in /home/root/.ssh/id_rsa.
Your public key has been saved in /home/root/.ssh/id_rsa.pub.
The key fingerprint is:
33:b3:fe:af:95:95:18:11:31:d5:de:96:2f:f2:35:f9 root@local-host

Step 2: Copy the public key to remote-host using ssh-copy-id or you can copy manually in a remote server in the user's home directory

root@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
root@remote-host's password:
Now try logging into the machine, with "ssh 'remote-host'", and check in:

.ssh/authorized_keys

Step 3: Login to remote-host without entering the password

root@local-host$ ssh remote-host
Last login: Sun Nov 16 17:22:33 2008 from 192.168.1.2
[Note: SSH did not ask for password.]

root@remote-host$ [Note: You are on remote-host here]

 in case  No identities found the use below commands


If you have loaded keys to the ssh-agent using the ssh-add, then ssh-copy-id will get the keys from the ssh-agent to copy to the remote-host. i.e, it copies the keys provided by ssh-add -L command to the remote-host, when you don’t pass option -i to the ssh-copy-id.

root@local-host$ ssh-add -L
The agent has no identities.

root@local-host$ ssh-add
Identity added: /home/root/.ssh/id_rsa (/home/root/.ssh/id_rsa) 

root@local-host$ ssh-add -L

ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAsJIEILxftj8aSxMa3d8t6JvM79DyBV
aHrtPhTYpq7kIEMUNzApnyxsHpH1tQ/Ow== /home/root/.ssh/id_rsa