How to mirror a Git Repo using Jenkins and access the Git Mirror

Posted on February 27, 2025

A Git mirror is a complete copy of a Git repository. It’s a type of Git repository that is a mirror image of another repository, often used for backup, collaboration, or deployment purposes.

Some key aspects of a Git mirror:

Characteristics

  • Read-only or read-write: A Git mirror can be either read-only, where updates are pushed from the original repository, or read-write, where updates can be pushed to both the mirror and the original repository.
  • Complete copy: A Git mirror contains all the branches, tags, and commits of the original repository.
  • Independent: A Git mirror is a separate Git repository, with its own Git directory and configuration.

Use cases

  • Backup and disaster recovery: A Git mirror can serve as a backup of the original repository, ensuring that the codebase is preserved in case of a disaster.
  • Collaboration and deployment: A Git mirror can be used to collaborate with external teams or to deploy code to a production environment.

Commands

  • Git clone with –mirror: The git clone command with the --mirror option can be used to create a Git mirror.
  • Git push with –mirror: The git push command with the --mirror option can be used to update a Git mirror.
  • Git remote with –mirror: The git remote command with the --mirror option can be used to add a Git mirror as a remote repository.

How to setup

1) Configure the Git credentials using the Credentials Manager of Jenkins

2) Configure the credentials on your Jenkins job:

Build Triggers

  • Check: Poll SCM
    • Schedule: H * * * *

Build Environment

  • Check: Delete workspace before build starts
  • Check: Use secret text(s) or file(s)
    • Bindings
      • Username and password (separated)
        • Username Variable: GIT_USERNAME
        • Password Variable: GIT_PAT
      • Credentials
        • Select: Specific credentials
          • Select the Jenkins credentials for the Git repo.

3) Add this as the Execute shell step:

#!/bin/bash

# Set the GIT_ASKPASS environment variable
export GIT_ASKPASS=true

# Use the bound credentials
echo "GIT_USERNAME: $GIT_USERNAME"
# Extract the UserID if the username is an email
GIT_USERID=$(echo "$GIT_USERNAME" | cut -d "@" -f 1)
echo "GIT_USERID: $GIT_USERID"

# Use the credentials
"Running Git Mirror of the repo ..."
git -c credential.helper="" clone --mirror "https://${GIT_USERID}:${GIT_PAT}@github.com/sample-repo.git"
echo "Done"

4) Save the output of the Jenkins job as an artifact.

How to access this Git Mirror

$ cd "/var/lib/jenkins/workspace/<your-jenkins-job-name>/sample-repo.git"
$ git config --global --add safe.directory . # Incase you get any warnings
$ git daemon --base-path=. --export-all --reuseaddr --verbose --port=9000

This will start a Git Server and serve the git repo via the git protocol.

Now you can clone the repo using this command:

git clone git://<your-jenkins-server>:9000/sample-repo.git

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