How to SSH Remote Login without Password in Linux/Mac

When we access a machine, it prompts for password for the corresponding user. However, it is tiresome, if need to access frequently, and each time we have to type the password.

In this post, we will learn how to ssh login to a remote computer without typing password each time we access later.

Let’s take a look how we need to configure key-pairs in both- local and remote machines.

Local Machine

Usually, in the user home directory, there is a hidden directory named .ssh. We will generate key-pairs in that directory. If there is no such directory, create one using the command mkdir .ssh

Generate Key-pair

Now, generate key-pair using the command ssh-keygen and set a name for the key files. Here, I have chosen the name as rsa.

<user@local>:~$ cd .ssh
<user@local>:~$ ssh-keygen -t rsa

Follow the instructions and then two files will be created named as- rsa and rsa.pub.

Add Key to the Keychain

Now, let’s add the key to the authentication agent using the command ssh-add.

<user@local>:~$ ssh-add ~/.ssh/rsa

We can check if the key has been added in the authentication agent.

<user@local>:~$ ssh-add -l

Remote Machine

All we need to do in a remote machine is to add the generated public key in the ~/.ssh/authorized_keys file. Create the file if there is none.

Add public key

Copy the contents of the public key (.pub) from your local machine.

<user@local>:~$ cat ~/.ssh/rsa.pub
Output>
	ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCre9snImDkV6SflHBMhNYMaKty+ADpeKAs5cJi3z/SGIwuH/eWOkVIFCkZye/BdKurtuX8rtXYXudQCXZ8arzHdaeTwP135e8fefDDZ9cMqyyCf0IlCkLw0ydrInfPzpsu2L2pqlqUiM2Urjpo0AVF4XuBbo/RBcXe49l91AFkjvrBSFIaxlRCV36R5NYBGmLqSEDTDSpmspxjaa2bbwT0X/oS+WQkp6FHHX0x67YeoEjf1qP5DMmbWKeiyqJeMkdhmeVjlnuFLkpZrS+m2vuchmuCHrGkNov6FjLTalE2Koe1YxzI13GpDMFZglFWoz7CfJWHtv9ZD5oQgAssNTwj mrx@mrx-Inspiron-5548

Now, append the key content in the authorized_keys file of your remote machine.

<user@remote>:~$ sudo nano ~/.ssh/authorized_keys

Now, you can ssh to the device without password. Suppose the IP address of the remote device is 192.168.1.5. So, you can ssh now using the following command:

<user@local>:~$ ssh remote_user@192.168.1.5

That’s all!!!