How to create ssh key linux

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Generating a new SSH key and adding it to the ssh-agent

After you’ve checked for existing SSH keys, you can generate a new SSH key to use for authentication, then add it to the ssh-agent.

About SSH key generation

If you don’t already have an SSH key, you must generate a new SSH key to use for authentication. If you’re unsure whether you already have an SSH key, you can check for existing keys. For more information, see «Checking for existing SSH keys.»

If you want to use a hardware security key to authenticate to GitHub, you must generate a new SSH key for your hardware security key. You must connect your hardware security key to your computer when you authenticate with the key pair. For more information, see the OpenSSH 8.2 release notes.

If you don’t want to reenter your passphrase every time you use your SSH key, you can add your key to the SSH agent, which manages your SSH keys and remembers your passphrase.

Generating a new SSH key

Open Terminal Terminal Git Bash .

Paste the text below, substituting in your GitHub email address.

Note: If you are using a legacy system that doesn’t support the Ed25519 algorithm, use:

This creates a new SSH key, using the provided email as a label.

When you’re prompted to «Enter a file in which to save the key,» press Enter. This accepts the default file location.

At the prompt, type a secure passphrase. For more information, see «Working with SSH key passphrases.»

Adding your SSH key to the ssh-agent

Before adding a new SSH key to the ssh-agent to manage your keys, you should have checked for existing SSH keys and generated a new SSH key. When adding your SSH key to the agent, use the default macOS ssh-add command, and not an application installed by macports, homebrew, or some other external source.

Start the ssh-agent in the background.

Depending on your environment, you may need to use a different command. For example, you may need to use root access by running sudo -s -H before starting the ssh-agent, or you may need to use exec ssh-agent bash or exec ssh-agent zsh to run the ssh-agent.

If you’re using macOS Sierra 10.12.2 or later, you will need to modify your

/.ssh/config file to automatically load keys into the ssh-agent and store passphrases in your keychain.

First, check to see if your

/.ssh/config file exists in the default location.

If the file doesn’t exist, create the file.

/.ssh/config file, then modify the file to contain the following lines. If your SSH key file has a different name or path than the example code, modify the filename or path to match your current setup.

Note: If you chose not to add a passphrase to your key, you should omit the UseKeychain line.

Note: If you see an error like this

add an additional config line to your Host * section:

Add your SSH private key to the ssh-agent and store your passphrase in the keychain. If you created your key with a different name, or if you are adding an existing key that has a different name, replace id_ed25519 in the command with the name of your private key file.

Note: The -K option is Apple’s standard version of ssh-add , which stores the passphrase in your keychain for you when you add an SSH key to the ssh-agent. If you chose not to add a passphrase to your key, run the command without the -K option.

If you don’t have Apple’s standard version installed, you may receive an error. For more information on resolving this error, see «Error: ssh-add: illegal option — K.»

Add the SSH key to your account on GitHub. For more information, see «Adding a new SSH key to your GitHub account.»

If you have GitHub Desktop installed, you can use it to clone repositories and not deal with SSH keys.

Ensure the ssh-agent is running. You can use the «Auto-launching the ssh-agent» instructions in «Working with SSH key passphrases», or start it manually:

Add your SSH private key to the ssh-agent. If you created your key with a different name, or if you are adding an existing key that has a different name, replace id_ed25519 in the command with the name of your private key file.

Add the SSH key to your account on GitHub. For more information, see «Adding a new SSH key to your GitHub account.»

Start the ssh-agent in the background.

Depending on your environment, you may need to use a different command. For example, you may need to use root access by running sudo -s -H before starting the ssh-agent, or you may need to use exec ssh-agent bash or exec ssh-agent zsh to run the ssh-agent.

Add your SSH private key to the ssh-agent. If you created your key with a different name, or if you are adding an existing key that has a different name, replace id_ed25519 in the command with the name of your private key file.

Add the SSH key to your account on GitHub. For more information, see «Adding a new SSH key to your GitHub account.»

Generating a new SSH key for a hardware security key

If you are using macOS or Linux, you may need to update your SSH client or install a new SSH client prior to generating a new SSH key. For more information, see «Error: Unknown key type.»

Insert your hardware security key into your computer.

Open Terminal Terminal Git Bash .

Paste the text below, substituting in the email address for your account on GitHub.

Note: If the command fails and you receive the error invalid format or feature not supported, you may be using a hardware security key that does not support the Ed25519 algorithm. Enter the following command instead.

When you are prompted, touch the button on your hardware security key.

When you are prompted to «Enter a file in which to save the key,» press Enter to accept the default file location.

When you are prompted to type a passphrase, press Enter.

Add the SSH key to your account on GitHub. For more information, see «Adding a new SSH key to your GitHub account.»

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How To Create SSH Keys with OpenSSH on macOS, Linux, or Windows Subsystem for Linux

Published on December 1, 2020

Introduction

When setting up a remote Linux server, you’ll need to decide upon a method for securely connecting to it. While passwords are one way of verifying a user’s identity, passwords have multiple vulnerabilities and can be cracked by a brute force attack. Secure Shell keys — better known as SSH keys — are often used instead of passwords, as they offer a more secure method of connecting to remote Linux servers. As part of the Secure Shell cryptographic network protocol, SSH keys also enable users to securely perform network services over an unsecured network, such as delivering text-based commands to a remote server or configuring its services.

This tutorial will guide you through the steps of creating SSH keys with OpenSSH, a suite of open source SSH tools, on macOS and Linux, as well as on Windows through the use of the Windows Subsystem for Linux. It is written for an audience that is just getting started with the command line and will provide guidance on accessing the terminal on a personal computer. After completing this tutorial, you will have SSH keys that can be used to securely set up a server in the tutorial How To Set Up an Ubuntu 20.04 Server on a DigitalOcean Droplet that is part of the Introduction to the Cloud Curriculum.

If you are already familiar with the command line and looking for instructions on using SSH to connect to a remote server, please see our collection of tutorials on Setting Up SSH Keys for a range of Linux operating systems.

Prerequisites

To complete this tutorial, you will need:

• A local machine running one of the following operating systems: macOS, Linux, or Windows with Windows Subsystem for Linux installed. If you are using Windows, you can find instructions for downloading or updating the Windows Subsystem for Linux on Microsoft’s documentation page. Note that while OpenSSH should work for a range of Linux distributions, this tutorial has been tested using Ubuntu 20.04.

Note: If you are looking for instructions on how to create SSH keys on a Windows machine that does not have the Windows Subsystem for Linux, please visit our product documentation How to Create SSH Keys with PuTTY on Windows.

• Some familiarity with working with a terminal and the command line. If you need an introduction to working with terminals and the command line, you can visit our guide A Linux Command Line Primer.

Step 1 — Understanding SSH Keys

SSH keys are two long strings of characters that can be used to authenticate the identity of a user requesting access to a remote server. These keys are generated by the user on their local computer using a SSH utility. One key is private and stored on the user’s local machine. The other key is public and shared with the remote server or any other entity the user wishes to securely communicate with.

When a user requests to connect to a server with SSH, the server sends a message encrypted with the public key that can only be decrypted by the associated private key. The user’s local machine then uses its private key to attempt to decrypt the message. If the message is successfully decrypted, the server grants the user access without the need of a password. Once authenticated, users can launch a remote shell session in their local terminal to deliver text-based commands to the remote server.

In the next step, you will open a terminal on your computer so that you can access the SSH utility used to generate a pair of SSH keys.

Step 2 — Opening a Terminal on Your Computer

A terminal allows you to interact with your computer through text-based commands rather than a graphical user interface. The way you access the terminal on your computer will depend on what type of operating system you are using.

On machines running macOS, the Terminal application is typically located in the Utilities folder inside the Applications folder. You can also find it by searching for “terminal” in the Search Spotlight.

If you are working on a Linux computer, your distribution’s default terminal application is also typically located in the Utilities folder inside the Applications folder. You can also find it by searching for “terminal” with the Desktop search functionality.

If you are working on a Windows machine running Windows Subsystem for Linux, a Linux terminal should open immediately after installation. You can also find it by searching for “Ubuntu” with the Desktop search functionality.

Once you have located your system’s terminal application, open up a new terminal window. Your terminal should display your user name, a dollar sign ( $ ), and a cursor. This is where you will begin to type commands to tell the terminal what to do.

In the next step, you will enter a text-based command to generate a pair of SSH keys.

Step 3 — Generating Keys With OpenSSH

Your macOS or Linux operating system should have the standard OpenSSH suite of tools already installed. This suite of tools includes the utility ssh-keygen , which you will use to generate a pair of SSH keys.

Type the following command into your terminal:

You will then be prompted to select a location for the keys. By default, the keys are stored in the

/.ssh directory with the filenames id_rsa for the private key and id_rsa.pub for the public key. Using the default locations allows your SSH client to automatically find your SSH keys when authenticating, so we recommend accepting these default options. To do so, press ENTER :

Warning: If you have previously generated a key pair, you will be prompted to confirm that you actually want to overwrite the existing key:

If you choose to overwrite the key on disk, you will not be able to authenticate using the previous key anymore. Selecting “yes” is an irreversible destructive process.

If you’re certain that you want to overwrite the existing key on disk, you can do so by pressing Y and then ENTER .

If you choose the default location, your public key will be located in /home/ sammy /.ssh/id_rsa.pub and your private key will be located in /home/ sammy /.ssh/id_rsa . Note that in your filepath, sammy will be replaced with your username.

After selecting a location for the key, you’ll be prompted to enter an optional passphrase which encrypts the private key file on disk.

If you enter a passphrase, you will have to provide it every time you use this key (unless you are running SSH agent software that stores the decrypted key). We recommend using a passphrase, but you can just press ENTER to bypass this prompt:

Following that final prompt, your system will generate the SSH key pair:

You now have a public and private key that you can use to authenticate.

Conclusion

Congratulations, you have now generated a pair of SSH keys. These keys can be used to securely connect with a remote server and are necessary for the tutorial How To Set Up an Ubuntu 20.04 Server on a DigitalOcean Droplet that follows this tutorial in the Introduction to the Cloud Curriculum.

For a deeper dive on working using SSH, please visit our guide SSH Essentials: Working With SSH Servers, Clients, and Keys.

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