How to create ssh key in linux

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 passphrases

You can access and write data in repositories on GitHub.com using SSH (Secure Shell Protocol). When you connect via SSH, you authenticate using a private key file on your local machine. For more information, see «About SSH.»

When you generate an SSH key, you can add a passphrase to further secure the key. Whenever you use the key, you must enter the passphrase. If your key has a passphrase and you don’t want to enter the passphrase every time you use the key, you can add your key to the SSH agent. The SSH agent manages your SSH keys and remembers your passphrase.

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.

Generating a new SSH key

You can generate a new SSH key on your local machine. After you generate the key, you can add the public key to your account on GitHub.com to enable authentication for Git operations over SSH.

Note: GitHub improved security by dropping older, insecure key types on March 15, 2022.

As of that date, DSA keys ( ssh-dss ) are no longer supported. You cannot add new DSA keys to your personal account on GitHub.com.

RSA keys ( ssh-rsa ) with a valid_after before November 2, 2021 may continue to use any signature algorithm. RSA keys generated after that date must use a SHA-2 signature algorithm. Some older clients may need to be upgraded in order to use SHA-2 signatures.

1. Open Terminal Terminal Git Bash .
2. Paste the text below, substituting in your GitHub email address.

ssh-keygen -t ed25519 -C "your_email@example.com"

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

> Generating public/private ALGORITHM key pair.

When you’re prompted to «Enter a file in which to save the key», you can press Enter to accept the default file location. Please note that if you created SSH keys previously, ssh-keygen may ask you to rewrite another key, in which case we recommend creating a custom-named SSH key. To do so, type the default file location and replace id_ssh_keyname with your custom key name.

> Enter a file in which to save the key (/Users/YOU/.ssh/id_ALGORITHM): [Press enter]

> Enter a file in which to save the key (/c/Users/YOU/.ssh/id_ALGORITHM):[Press enter]

> Enter a file in which to save the key (/home/YOU/.ssh/ALGORITHM):[Press enter]

> Enter passphrase (empty for no passphrase): [Type a passphrase] > Enter same passphrase again: [Type passphrase again]

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.

$ eval "$(ssh-agent -s)" > Agent pid 59566

$ open ~/.ssh/config > The file /Users/YOU/.ssh/config does not exist.

Host github.com AddKeysToAgent yes UseKeychain yes IdentityFile ~/.ssh/id_ed25519 

• If you chose not to add a passphrase to your key, you should omit the UseKeychain line.
• If you see a Bad configuration option: usekeychain error, add an additional line to the configuration’s’ Host *.github.com section.

Host github.com IgnoreUnknown UseKeychain 

ssh-add --apple-use-keychain ~/.ssh/id_ed25519

Note: The —apple-use-keychain option 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 —apple-use-keychain option. The —apple-use-keychain option is in Apple’s standard version of ssh-add . In MacOS versions prior to Monterey (12.0), the —apple-use-keychain and —apple-load-keychain flags used the syntax -K and -A , respectively. If you don’t have Apple’s standard version of ssh-add installed, you may receive an error. For more information, see «Error: ssh-add: illegal option — K.» If you continue to be prompted for your passphrase, you may need to add the command to your ~/.zshrc file (or your ~/.bashrc file for bash).

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:

# start the ssh-agent in the background $ eval "$(ssh-agent -s)" > Agent pid 59566

$ eval "$(ssh-agent -s)" > Agent pid 59566

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.»

1. Insert your hardware security key into your computer.
2. Open Terminal Terminal Git Bash .
3. Paste the text below, substituting in the email address for your account on GitHub.

ssh-keygen -t ed25519-sk -C "YOUR_EMAIL"

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.

ssh-keygen -t ecdsa-sk -C "your_email@example.com"

> Enter a file in which to save the key (/Users/YOU/.ssh/id_ed25519_sk): [Press enter]

> Enter a file in which to save the key (/c/Users/YOU/.ssh/id_ed25519_sk):[Press enter]

> Enter a file in which to save the key (/home/YOU/.ssh/id_ed25519_sk):[Press enter]

> Enter passphrase (empty for no passphrase): [Type a passphrase] > Enter same passphrase again: [Type passphrase again]

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