Repository mirroring between GitLab and GitHub via SSH

Tldr

Set up automatic synchronization between your project and another repository usingSSH forGitLab andGitHub, enabling seamless pushing and pulling of changes.

🔗 Quick links

• GitLab Repository mirroring

🔧 Manual

1️⃣ GitLab

Prerequisites

You must have at least the Maintainer role for the project.

Steps

1. On the left sidebar, select Search or go to and find your project.

2. Select Settings > Repository.

3. Expand Mirroring repositories.

4. Select Add new.

5. Enter a Git repository URL. For security reasons, the URL to the original repository is only displayed to users with the Maintainer role or the Owner role for the mirrored project.

   Don't forget : with / in the URL.

   The proper format for the URL is:

   ssh://github.com/_OWNER_/_REPOSITORY_.git
   

6. Select a Mirror direction.

7. Choose either:

   • Detect host keys: GitLab fetches the host keys from the server and displays the fingerprints.
   • Input host keys manually, and enter the host key into SSH host key.

   When mirroring the repository, GitLab confirms at least one of the stored host keys matches before connecting. This check can protect your mirror from malicious code injections, or your password from being stolen.

8. Select an SSH public key in Authentication method.

9. Optionally: provide a username and select options for Mirror triggers.

10. Submit by clicking on Mirror repository.

11. Copy the SSH public key and add it to the repository you want to mirror. This key is used to authenticate the connection between the two repositories.

2️⃣ GitHub

Prerequisites

You must have admin access to the repository you want to mirror.

Steps

1. Find your repository on GitHub.
2. Select Settings.
3. Under Security, select Deploy keys.
4. Select Add deploy key.
5. Enter a Title for the key and paste the SSH public key you copied from GitLab.
6. Check Allow write access if you want to push changes from GitLab to GitHub.
7. Submit by clicking on Add key.

3️⃣ Check the status

1. Go back to GitLab.
2. Click Update now to check the status of the mirroring process.