Public key authentication can allow you to log into remote systems via SSH without a password. Even though you will not need a password to log into a system, you will need to have access to the key. Be sure to keep your key in a secure location.
Here is an example of creating a passwordless connection from linuxsvr01 to linuxsvr02 using SSH public key authentication.
1. Create an SSH Key
Use the ssh-keygen command to create an SSH key. Accept all the defaults by pressing ENTER at every prompt. You’ll want to leave the passphrase empty.
linuxsvr01$ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/home/user/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/user/.ssh/id_rsa. Your public key has been saved in /home/user/.ssh/id_rsa.pub. The key fingerprint is: b2:ad:a0:80:85:ad:6c:16:bd:1c:e7:63:4f:a0:00:15 user@host The key's randomart image is: +---[RSA 2048]----+ | . o + | | = X * . | | . O @ = . .| | + o X O . + | | . = S * = o | | . ..o . . o . | | + .o. E | | + ...o. | | . . ooo+. | +----[SHA256]-----+ linuxsvr01$
Note: You can optionally add a passphrase for the key itself. If you do use a passphrase, then you will have to use an ssh-agent to cache the passphrase. While the passphrase is cached you can connect without entering in the passphrase.
2. Copy the SSH Public Key to the Remote Host
linuxsvr01$ ssh-copy-id root@linuxsvr02 root@linuxsvr02's password: linuxsvr01$
3. Login to the Remote Host Without a Password
Now you can connect to the server without a password.
linuxsvr01$ ssh root@linuxsvr02 Last login: Tue Apr 22 11:35:41 2016 from 10.23.45.67 linuxsvr02#