GitLab to GitHub Repository Mirroring

Introduction

In software development, version control repositories are essential for managing codebases. At times, developers may need to synchronize repositories between platforms—such as GitLab and GitHub—to maintain backups, improve collaboration, or increase visibility. This guide demonstrates how to mirror a GitLab repository to GitHub in a step-by-step manner.

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What Is Mirroring?

Mirroring is the process of creating and maintaining an exact replica of a repository. Unlike forking, which only copies the current state, mirroring retains all branches, tags, commit histories, and references, and can stay continuously synchronized with the original.

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Why Mirror Repositories?

• Backup: Keep a secondary copy of your work.
• Cross-Platform Collaboration: Collaborate with users on different platforms.
• Continuous Sync: Keep GitHub updated automatically as changes are pushed to GitLab.
• Complete History: Retains commit history and branch structure, unlike forks.

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Objective

To configure push mirroring so that updates pushed to GitLab are automatically reflected in GitHub.

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Tools & Technologies Used

• GitLab: DevOps platform for source control and CI/CD
• GitHub: Widely used Git hosting platform for code collaboration
• Git (CLI): Command-line tool for version control
• PAT (Personal Access Token): Secure credential to authenticate between services

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Step-by-Step Mirroring Process

Step 1: Create GitHub Repository

1. Log in to GitHub.
2. Click on + ➝ New Repository.
3. Set repository name: Gitlab-Repo-Mirroring.
4. Select visibility: Public.
5. Check: “Initialize this repository with a README”.
6. Click Create Repository.

📷 Sample Screenshots:

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Step 2: Create Personal Access Token (PAT) on GitHub

1. Go to Settings ➝ Developer Settings.
2. Click Personal Access Tokens ➝ Tokens (classic).
3. Click Generate new token (classic).
4. Note description: "Mirroring GitLab to GitHub".
5. Select all scopes (full access).
6. Click Generate Token.
7. Copy and store the token securely. (One-time view only)

📷 Token Sample:

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Step 3: Create Project on GitLab

1. Log in to GitLab ➝ New Project ➝ Create Blank Project.
2. Project Name: GitHub-Repo-Mirroring.
3. URL Namespace: Select Users.
4. Visibility: Public.
5. Initialize repository with a README.
6. Click Create Project.

📷 GitLab Screenshots:

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Step 4: Configure GitLab Mirroring

1. Navigate to your GitLab project.
2. Go to Settings ➝ Repository.
3. Scroll to Mirroring repositories ➝ Click Add New Mirror.

📷 Step Flow:

Fill in the mirror form:

• Git Repository URL:
  • Go to GitHub ➝ Repository ➝ Code ➝ Copy HTTPS URL
    
• Authentication Method: Username + Token
  • Username: Your GitHub username
  • Password/Token: Paste the GitHub PAT you generated
• Click Mirror Repository

📷 Final Config:

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Step 5: Test the Mirroring

1. Clone your GitLab repository locally:

   git clone https://gitlab.com/<your-username>/GitHub-Repo-Mirroring.git
   cd GitHub-Repo-Mirroring

2. Create and add a new file:

touch testfile.txt
git add .
git commit -m "Added test file for mirror sync"
git push

3. Go to GitHub ➝ Refresh the repository ➝ Confirm testfile.txt appears.

4. Go to GitLab ➝ Refresh the repository ➝ Confirm testfile.txt appears.

Summary

This guide demonstrates how to set up automatic GitLab-to-GitHub mirroring using push mirroring with PAT authentication. Once configured, any change pushed to GitLab is automatically reflected in GitHub, enabling smooth backups and collaboration across both platforms.