The SSH daemon validates SSH client access by Linux system verification via /etc/passwd, or by public/private key cryptography approach.

By using the public/private cryptography approach, we can do a SSH without password.

In my write-up it is for root-to-root connection. You can use it for user connections.

Steps 1: At the Host Machine

1. Logon to the root home directory.
2. Make sure the hidden .ssh directory has the permission 700. If not execute the command

   # chmod 700 .ssh

3. Change Directory to .ssh directory by executing the command

   # cd .ssh

4. Generate the public-private keys using the ssh-keygen command.

   # ssh-keygen -t rsa

5. The resulting file id_rsa and id_rsa.pub rsa type public key

   # ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host

   (ssh-copy-id appends the keys to the remote-host’s .ssh/authorized_key)

Step 2: At the Remote Machine,

1. Test it out on the remote server

   # ssh remote-host

References

• SSH Auto Login Or Passwordless Login
• SSH Tutorial for LINUX
• 3 Steps to Perform SSH Login Without Password