# Build Docker Images on  Instances (BuildKit)

This guide explains how to install BuildKit, build Docker images from a Dockerfile, and push them to a registry on a Instance

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## 1. Install BuildKit
Download and extract BuildKit (example: v0.9.0):
```bash
wget https://github.com/moby/buildkit/releases/download/v0.9.0/buildkit-v0.9.0.linux-amd64.tar.gz
tar xvf buildkit-v0.9.0.linux-amd64.tar.gz
```

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## 2. Make `buildctl` Available
Option A: Temporary (session only):
```bash
export PATH=$PATH:$(pwd)/buildkit-v0.9.0.linux-amd64/bin
```

Option B: System-wide (requires sudo):
```bash
sudo cp buildkit-v0.9.0.linux-amd64/bin/buildctl /usr/local/bin/
sudo chmod +x /usr/local/bin/buildctl
```

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## 3. Verify Installation
```bash
buildctl --version
```

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## 4. Prepare a Dockerfile
Place your Dockerfile in the working directory. For testing, download a sample:
```bash
wget --no-check-certificate https://raw.githubusercontent.com/courselabs/kubernetes/main/labs/docker/simple/Dockerfile
```

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## 5. Build and Push an Image
First, configure registry authentication.

Encode your credentials:
```bash
echo -n "username:password" | base64
```

Create `$HOME/.docker/config.json` with this format (replace BASE64_TOKEN):
```json
{
  "auths": {
    "registry.e2enetworks.net": {
      "auth": "BASE64_TOKEN"
    }
  }
}
```

For Docker Hub, use `"https://index.docker.io/v1/"` as the registry key.

Now build and push the image:
```bash
buildctl --addr tcp://buildkit.internal:1234 build --frontend=dockerfile.v0 --local context=. --local dockerfile=. --output type=image,name=registry.e2enetworks.net/namespace/my-image:latest,push=true
```

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## 6. Troubleshooting
- **Auth errors** → Check base64 token and registry URL in config.json  
- **BuildKit not found** → Verify PATH or /usr/local/bin  
- **Network/DNS issues** → Ensure Instance can reach registry and BuildKit endpoint  
- **Permission denied** → Use sudo if installing system-wide

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