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RSA SSH keys

If you use RSA keys for SSH, the US National Institute of Standards and Technology recommends that you use a key size of at least 2048 bits. By default, the ssh-keygen command creates an 1024-bit RSA key.

You can create and configure an RSA key with the following command, substituting if desired for the minimum recommended key size of 2048:

ssh-keygen -t rsa -b 2048 -C "[email protected]"

The -C flag, with a quoted comment such as an email address, is an optional way to label your SSH keys.

You'll see a response similar to:

Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa):

##Testing that everything is set up correctly

To test whether your SSH key was added correctly, run the following command in your terminal (replacing gitlab.com with your GitLab's instance domain):

ssh -T [email protected]

The first time you connect to GitLab via SSH, you will be asked to verify the authenticity of the GitLab host that you're connecting to. For example, when connecting to GitLab.com, answer yes to add GitLab.com to the list of trusted hosts:

The authenticity of host 'gitlab.com (35.231.145.151)' can't be established.
ECDSA key fingerprint is SHA256:HbW3g8zUjNSksFbqTiUWPWg2Bq1x8xdGUrliXFzSnUw.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'gitlab.com' (ECDSA) to the list of known hosts.

Once added to the list of known hosts, you won't be asked to validate the authenticity of GitLab's host again. Run the above command once more, and you should only receive a Welcome to GitLab, @username! message.

If the welcome message doesn't appear, you can troubleshoot the problem by running ssh in verbose mode with the following command:

ssh -Tvvv [email protected]

Working with non-default SSH key pair paths

If you used a non-default file path for your GitLab SSH key pair configure your SSH client to point to your GitLab private SSH key. To make these changes, run the following commands:

eval $(ssh-agent -s)
ssh-add <path to private SSH key>

Now save these settings to the ~/.ssh/config file. Two examples for SSH keys dedicated to GitLab are shown here:

# GitLab.com
Host gitlab.com
  Preferredauthentications publickey
  IdentityFile ~/.ssh/gitlab_com_rsa

# Private GitLab instance
Host gitlab.company.com
  Preferredauthentications publickey
  IdentityFile ~/.ssh/example_com_rsa

Public SSH keys need to be unique to GitLab, as they will bind to your account.

Your SSH key is the only identifier you'll have when pushing code via SSH, that's why it needs to uniquely map to a single user.