Use SSH Keys to Access a Remote Linux Machine

April 23, 2019

Estimated time: 5m Difficulty: 2/5

This guide will explain how you can log in via SSH to a remote computer or server that is running Linux without using your password. As an added benefit, this process will also permit you to add the remote machine in question to your ssh config file, and thus to log into it by simply typing, e.g. ssh linuxserver from the command line.

Step 1

First, you will need to generate a set of SSH keys on your local computer — i.e. the one you’re using to SSH in to the remote Linux machine. If you already have a set of SSH keys installed on your local computer, you can skip this step.

If you do not have keys installed on your local computer, you can generate a set by running the following (replacing [note] with your own note, of course):


      ssh-keygen -t rsa -C "[note]"

There is no need to add a password to the key. This guide assumes that you will save the new keys in the suggested directory, which is ~/.ssh.

Step 2

Next, you will need to generate a set of SSH keys on the remote Linux machine — i.e., the one you’re logging into — so that the necessary ~/.ssh folder structure is created, along with the known_hosts file. If you have already done this, you can skip this step. If you have not, repeat the instructions above on your remote Linux machine.

Step 3

To copy your public SSH key over to the remote Linux machine, we will use cat. You will need to know:

  • The location in which your public SSH key is stored. If you installed the key using the exact process outlined in Step 1, this will be ~/.ssh/id_rsa.pub. If you saved the key elsewhere, make a note of its location on your local machine
  • The address of the remote Linux machine to which you want to add the key
  • Your username and password on the remote Linux machine to which you want to add the key

Supposing that the public SSH key is located at ~/.ssh/id_rsa.pub, your username on the remote Linux machine is charles, and your remote Linux machine’s IP address is 10.0.1.2, you can copy the key over by running:


      cat ~/.ssh/id_rsa.pub | ssh charles@10.0.1.2 'cat >> ~/.ssh/authorized_keys'

NOTE You will be prompted for your account password once you press enter.

Step 4

You will now be able to log in without using your password. To do this, you can type ssh followed by your username and the address of the remote Linux machine. In our example, this would be:


      ssh charles@10.0.1.2

Step 5

We strongly recommend saving your configuration in your SSH config file so that you can use easy-to-remember shortcuts to log in to all your devices. A full guide explaining how to do that can be found here.

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Categories
Linux

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