SSH or Secure Socket Shell is a network protocol used to access a system or server remotely in a secured way. It is an application layer protocol and it enables you to access another machine without physical access remotely via the internet. With SSH you can issue remote commands, transfer files, connect to remote servers, and can communicate between two computers in an encrypted way. You can log in to your remote SSH server by types:
Password Authentication Public Key Authentication (Passwordless)
Here we will discuss configuring key-based authentication for SSH login.
Step 1 – Generate SSH Key Pair
Firstly you would require generating a key pair (RSA or DSA), you can specify option RSA or DSA key using ‘-t’ command-line switch. If we do not pass the -t parameter, it will default create a RSA key. Follow the quick wizard: Now, you can see the generated key files with the following command.
Step 2 – Copy Public Key to Remote System
the ~/.ssh/authorized_key is the file responsible for keeping public keys of remote clients. During the key-based authentication, the system checks for the public keys in the same file. You can simply copy the content of public-key (file with .pub extension) from your system to the authorized_key file on the remote server. Otherwise, let it be done by running the following command. You will be asked for the remote_user password. Once you enter the correct password, the public key will be stored in the remote server.
Step 3 – Verify SSH without Password
Now as we have all done, simply try to ssh to the remote system. You will log in to the remote system without entering the password. You should log in automatically now, without prompting for the password. If in case, the system is prompted for the password, means the key is not correctly copied on the destination server. To resolve this, check the key is properly appended to the authorized_key file and its permissions.
Conclusion
In this tutorial, you have learned to create SSH key pair and configure key-based login between two systems.
