How to configure SSH public key authentication for password less login on Red Hat

Step 1: Generate SSH key pair using ssh-keygen command

# ssh-keygen

⦁ By default, ssh-keygen creates an RSA key pair of 2048 bits.

⦁ The default location is /home/<user>/.ssh/id_rsa (for the private key) and /home/<user>/.ssh/id_rsa.pub (for the public key)

Step 2: Copy public key generated into the authorized_keys file on the remote host

⦁ Method 1 - Copy public key to the remote machine

# scp $HOME/.ssh/id_rsa_key1.pub root@host.domain.com:/tmp

# cat /tmp/id_rsa_key1.pub >> /home/<user>/.ssh/authorized_keys (on remote host)

⦁ Method 2 - Instead of copy manually ssh-copy-id internally performs above commands

# ssh-copy-id -i ~/.ssh/id_rsa.pub user@remote-server

Step 3: Verify ownership and permissions of $HOME/.ssh and $HOME/.ssh/authorized_keys on the remote host

# chmod 700 ~/.ssh

# chmod 600 ~/.ssh/authorized_keys

# chown -R <user>:<user> /home/your_username/.ssh

Step 4: Login to remote machine without password (private key machine to public key machine)

⦁ Default Login

# ssh root@remote_host.domain.com

Last login: Tue April 7 13:35:01 2019 from 10.67.1.77

[root@host ~]#

⦁ Login with specified key

# ssh root@host.domain.com -i /root/.ssh/id_rsa_key1

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