The process of setting up SSH keys for GitLab involves generating a key pair on your local machine and then adding the public part of that key pair to your GitLab user account.

3.1 Generating an SSH Key
Pair

The primary tool for generating SSH keys is
`ssh-keygen`, available on most Unix-like systems (Linux, macOS) and through
Git Bash on Windows.

Open your terminal or Git Bash and run the
following command. It’s recommended to use the `ed25519` algorithm for better
security and performance, though `RSA` is also widely supported.

ssh-keygen -t ed25519 -C
“your_email@example.com”

When prompted, you can press Enter to accept
the default file location (`~/.ssh/id_ed25519`).

Generating public/private ed25519 key pair.
Enter
file in which to save the key (/home/user/.ssh/id_ed25519):
Enter
passphrase (empty for no passphrase):
Enter
same passphrase again:

Passphrase: It is highly recommended to set a strong passphrase for your
private key. This encrypts your private key on your disk, adding an extra layer
of security. Even if someone gains access to your computer, they cannot use
your SSH key without the passphrase. You will be prompted for this passphrase
once per session when you first use the key, or if you restart your SSH agent.

3.2 Copying the Public Key

After generation, your public key is stored in
a file with a `.pub` extension (e.g., `~/.ssh/id_ed25519.pub`). You need to
copy the *entire content* of this file to add it to GitLab.

On Linux/macOS: Use `cat` to display the content and copy it, or `pbcopy` (macOS)
/ `xclip` (Linux) to copy directly to the clipboard.

cat ~/.ssh/id_ed25519.pub

Or for direct copy:

pbcopy < ~/.ssh/id_ed25519.pub  # macOS
xclip
-sel clip < ~/.ssh/id_ed25519.pub # Linux (ensure xclip is installed)

On Windows (Git Bash):

cat ~/.ssh/id_ed25519.pub | clip

The output will look something like this
(single line):

ssh-ed25519
AAAAC3NzaC1lZDI1NTE5AAAAIC0s2Yh+…your_email@example.com

3.3 Adding the Key to GitLab

Now, navigate to your GitLab account in your
web browser:

1.        Log in
to your GitLab instance.

2.        Click on
your user avatar in the top right corner and select “Preferences”.

3.        In the
left sidebar, click on “SSH Keys”.

4.        In the
“Key” text area, paste the entire public key you copied earlier.

5.        Add a
descriptive “Title” for the key (e.g., “My Work Laptop”,
“Personal Desktop”).

6.        Optionally,
set an “Expiration date” for added security.

7.        Click
the “Add key” button.

Once added, you should see your key listed with
its fingerprint and creation date.

3.4 Verifying the SSH Connection

To
confirm your SSH key is correctly set up and GitLab can authenticate you, run a
test command:

ssh -T git@gitlab.com

(Replace
`gitlab.com` with your private GitLab instance domain if applicable.)

You
might see a warning about adding `gitlab.com` to your list of known hosts the
first time. Type `yes` and press Enter. If successful, GitLab will respond with
a welcome message, typically stating your username:

Welcome to GitLab,
@your_username!

If you encounter
“Permission denied (publickey)”, double-check that your public key
was correctly copied and added to GitLab, and that your private key has the
correct permissions (read-only for user: `chmod 400 ~/.ssh/id_ed25519`). Ensure
your SSH agent is running if you are using a passphrase.