Docker Container SSH Git Clone

Clone a GitHub repo (via SSH) into a Docker container using the host's SSH key.

Steps

1. Create container (if not exists):

   docker run -d --name <name> -v ~/MountDir:/data --restart unless-stopped ubuntu:24.04 sleep 86400
   

2. Install git and openssh inside the container:

   docker exec <name> apt-get update && docker exec <name> apt-get install -y git openssh-client
   

3. Copy SSH key from host to container:

   docker exec <name> mkdir -p /root/.ssh
   docker cp ~/.ssh/id_ed25519 <name>:/root/.ssh/id_ed25519
   docker cp ~/.ssh/id_ed25519.pub <name>:/root/.ssh/id_ed25519.pub
   

4. Set permissions and SSH config, then clone:

   docker exec <name> sh -c "
     chmod 700 /root/.ssh && chmod 600 /root/.ssh/id_ed25519 && chmod 644 /root/.ssh/id_ed25519.pub &&
     echo 'Host github.com
       HostName github.com
       User git
       IdentityFile /root/.ssh/id_ed25519
       StrictHostKeyChecking no' > /root/.ssh/config &&
     git clone git@github.com:<owner>/<repo>.git /data/<repo>
   "
   

Pitfalls

• HTTPS with token fails inside container — docker exec has no interactive credential helper. Use SSH instead.
• SSH key permissions must be correct (700 for .ssh, 600 for private key, 644 for public key).
• StrictHostKeyChecking no is needed to avoid interactive prompt on first connect.
• docker cp fails if target directory doesn't exist — create it first with docker exec.
• If the container already has /root/.ssh, skip the mkdir step.