The ssh-agent program is an authentication agent that handles passwords for SSH private keys. Use ssh-add to add the keys to the list maintained by ssh-agent. After you add a private key password to ssh-agent, you do not need to enter it each time you connect to a remote host with your public key.
Generating authentication key pairs
Use the ssh-keygen command to generate authentication key pairs as described below. Provide a passphrase, for example “password”, when creating the key pairs.
# ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/id_rsa. Your public key has been saved in /root/.ssh/id_rsa.pub. The key fingerprint is: SHA256:4lYqkqgXmhIxoyMdT+ZfGFCxeMUqTnXLjrRQKjbEC/U root@geeklab The key's randomart image is: +---[RSA 2048]----+ | o. .oo. | |. o...ooo | | o .E=o+ . | |+ * B.+ o | |.* @ +.*S | |=.o.+.++o | |o=o...+. | |= .. o. | |o. | +----[SHA256]-----+
Copy the Public key to remote host
1. Copy the public key to ~/.ssh/authorized_keys on the remote system.
# ssh-copy-id -i ~/.ssh/id_rsa.pub firstname.lastname@example.org
2. Now try logging into the machine, with “ssh ‘email@example.com′”, and check in the .ssh/authorized_keys file to make sure we haven’t added extra keys that you weren’t expecting.
$ ssh 192.168.12.10 Enter passphrase for key '/root/.ssh/id_rsa': Last login: Wed Apr 06 09:03:50 2014 from 192.168.12.20
Add private key password to ssh-agent
1. To add the private key password to ssh-agent, enter the following command:
# exec ssh-agent $SHELL
2. The next step is to use the ssh-add command to add the key.
# ssh-add Enter passphrase for /root/.ssh/id_rsa: Identity added: /root/.ssh/id_rsa (/root/.ssh/id_rsa)
3. The “ssh-add -l” command lists fingerprints of all identities currently represented by the agent.
# ssh-add -l 2048 SHA256:4lYqkqgXmhIxoyMdT+ZfGFCxeMUqTnXLjrRQKjbEC/U /root/.ssh/id_rsa (RSA)
4. You can try loggin in to the remote system without password now.
$ ssh 192.168.12.10 Last login: Thu Apr 06 11:13:29 2014 from 192.168.12.20
In this example, the passphrase is remembered for only the current login session and is forgotten when you log out.