Generating a new SSH key pair

To generate a new SSH key pair, use the following command:

Git Bash on Windows / GNU/Linux / macOS:

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

Windows:

Alternatively on Windows you can download
PuttyGen
and follow this documentation article to generate a SSH key pair.

Next, you will be prompted to input a file path to save your SSH key pair to.

If you don't already have an SSH key pair use the suggested path by pressing
enter. Using the suggested path will normally allow your SSH client
to automatically use the SSH key pair with no additional configuration.

If you already have a SSH key pair with the suggested file path, you will need
to input a new file path and declare what host this SSH key pair will be used
for in your .ssh/config file, see Working with non-default SSH key pair paths
for more information.

Once you have input a file path you will be prompted to input a password to
secure your SSH key pair. It is a best practice to use a password for an SSH
key pair, but it is not required and you can skip creating a password by
pressing enter.

NOTE: Note:
If you want to change the password of your SSH key pair, you can use
ssh-keygen -p <keyname>.

The next step is to copy the public SSH key as we will need it afterwards.

To copy your public SSH key to the clipboard, use the appropriate code below:

macOS:

pbcopy < ~/.ssh/id_rsa.pub
GNU/Linux (requires the xclip package):

xclip -sel clip < ~/.ssh/id_rsa.pub
Windows Command Line:

type %userprofile%.ssh\id_rsa.pub | clip
Git Bash on Windows / Windows PowerShell:

cat ~/.ssh/id_rsa.pub | clip

The final step is to add your public SSH key to GitLab.

Navigate to the 'SSH Keys' tab in your 'Profile Settings'.
Paste your key in the 'Key' section and give it a relevant 'Title'.
Use an identifiable title like 'Work Laptop - Windows 7' or
'Home MacBook Pro 15'.

If you manually copied your public SSH key make sure you copied the entire
key starting with ssh-rsa and ending with your email.

Optionally you can test your setup by running ssh -T git@example.com
(replacing example.com with your GitLab domain) and verifying that you
receive a Welcome to GitLab message.

Working with non-default SSH key pair paths

If you used a non-default file path for your GitLab SSH key pair,
you must configure your SSH client to find your GitLab private SSH key
for connections to your GitLab server (perhaps gitlab.com).

For your current terminal session you can do so using the following commands
(replacing other_id_rsa with your private SSH key):

Git Bash on Windows / GNU/Linux / macOS:

eval $(ssh-agent -s)
ssh-add ~/.ssh/other_id_rsa
To retain these settings you'll need to save them to a configuration file.
For OpenSSH clients this is configured in the ~/.ssh/config file for some
operating systems.
Below are two example host configurations using their own SSH key:

GitLab.com server

Host gitlab.com
RSAAuthentication yes
IdentityFile ~/.ssh/config/private-key-filename-01

Private GitLab server

Host gitlab.company.com
RSAAuthentication yes
IdentityFile ~/.ssh/config/private-key-filename
Due to the wide variety of SSH clients and their very large number of
configuration options, further explanation of these topics is beyond the scope
of this document.

Public SSH keys need to be unique, 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.

Deploy keys

Per-repository deploy keys

Deploy keys allow read-only or read-write (if enabled) access to one or
multiple projects with a single SSH key pair.

This is really useful for cloning repositories to your Continuous
Integration (CI) server. By using deploy keys, you don't have to set up a
dummy user account.

If you are a project maintainer or owner, you can add a deploy key in the
project settings under the section 'Repository'. Specify a title for the new
deploy key and paste a public SSH key. After this, the machine that uses
the corresponding private SSH key has read-only or read-write (if enabled)
access to the project.

You can't add the same deploy key twice using the form.
If you want to add the same key to another project, please enable it in the
list that says 'Deploy keys from projects available to you'. All the deploy
keys of all the projects you have access to are available. This project
access can happen through being a direct member of the project, or through
a group.

Deploy keys can be shared between projects, you just need to add them to each
project.

Global shared deploy keys

Global Shared Deploy keys allow read-only or read-write (if enabled) access to
be configured on any repository in the entire GitLab installation.

This is really useful for integrating repositories to secured, shared Continuous
Integration (CI) services or other shared services.
GitLab administrators can set up the Global Shared Deploy key in GitLab and
add the private key to any shared systems. Individual repositories opt into
exposing their repository using these keys when a project maintainers (or higher)
authorizes a Global Shared Deploy key to be used with their project.

Global Shared Keys can provide greater security compared to Per-Project Deploy
Keys since an administrator of the target integrated system is the only one
who needs to know and configure the private key.

GitLab administrators set up Global Deploy keys in the Admin area under the
section Deploy Keys. Ensure keys have a meaningful title as that will be
the primary way for project maintainers and owners to identify the correct Global
Deploy key to add. For instance, if the key gives access to a SaaS CI instance,
use the name of that service in the key name if that is all it is used for.
When creating Global Shared Deploy keys, give some thought to the granularity
of keys - they could be of very narrow usage such as just a specific service or
of broader usage for something like "Anywhere you need to give read access to
your repository".

Once a GitLab administrator adds the Global Deployment key, project maintainers
and owners can add it in project's Settings > Repository section by expanding the
Deploy Key section and clicking Enable next to the appropriate key listed
under Public deploy keys available to any project.

NOTE: Note:
The heading Public deploy keys available to any project only appears
if there is at least one Global Deploy Key configured.

CAUTION: Warning:
Defining Global Deploy Keys does not expose any given repository via
the key until that repository adds the Global Deploy Key to their project.
In this way the Global Deploy Keys enable access by other systems, but do
not implicitly give any access just by setting them up.

Applications

Eclipse

How to add your SSH key to Eclipse: https://wiki.eclipse.org/EGit/User_Guide#Eclipse_SSH_Configuration

SSH on the GitLab server

GitLab integrates with the system-installed SSH daemon, designating a user
(typically named git) through which all access requests are handled. Users
connecting to the GitLab server over SSH are identified by their SSH key instead
of their username.

SSH client operations performed on the GitLab server wil be executed as this
user. Although it is possible to modify the SSH configuration for this user to,
e.g., provide a private SSH key to authenticate these requests by, this practice
is not supported and is strongly discouraged as it presents significant
security risks.

The GitLab check process includes a check for this condition, and will direct you
to this section if your server is configured like this, e.g.:

$ gitlab-rake gitlab:check

...

Git user has default SSH configuration? ... no
Try fixing it:
mkdir ~/gitlab-check-backup-1504540051
sudo mv /var/lib/git/.ssh/id_rsa ~/gitlab-check-backup-1504540051
sudo mv /var/lib/git/.ssh/id_rsa.pub ~/gitlab-check-backup-1504540051
For more information see:
doc/ssh/README.md in section "SSH on the GitLab server"
Please fix the error above and rerun the checks.
Remove the custom configuration as soon as you're able to. These customizations
are explicitly not supported and may stop working at any time.

Troubleshooting

If on Git clone you are prompted for a password like git@gitlab.com's password:
something is wrong with your SSH setup.

Ensure that you generated your SSH key pair correctly and added the public SSH
key to your GitLab profile
Try manually registering your private SSH key using ssh-agent as documented
earlier in this document
Try to debug the connection by running ssh -Tv git@example.com
(replacing example.com with your GitLab domain)