dockvirt

Example 2: Python (Flask) Web Application

This example shows how to run a simple Python Flask application using dockvirt.

Steps to Run

1. Start the VM with dockvirt: The Dockerfile and application files will be automatically copied to the VM and built there: Use the .dockvirt file for maximum convenience:

   # Build happens inside the VM automatically.
   # Optional (not required): pre-build on host
   # docker build -t my-flask-app:latest .
   
   # Use the default configuration from the .dockvirt file
   dockvirt up
       
   # Developer tip: if another dockvirt is first on your PATH (e.g., Homebrew),
   # use the project venv binary explicitly to ensure the latest local CLI:
   # ../../.venv-3.13/bin/dockvirt up
       
   # Or change the OS to Fedora (edit .dockvirt or use the parameter)
   dockvirt up --os fedora38
   

   You can also ignore the .dockvirt file and use full parameters:

   # Full command with parameters
   dockvirt up \
     --name flask-app \
     --domain flask-app.local \
     --image my-flask-app:latest \
     --port 5000 \
     --os ubuntu22.04
   

2. Add an entry to /etc/hosts: After getting the IP address from dockvirt, add it to your /etc/hosts file:

   <ip_address> flask-app.local
   

   If a reverse proxy (Caddy) is used inside the VM, IP-based checks may require a Host header:

   curl -H 'Host: flask-app.local' http://<ip_address>/
   

3. Open the application in your browser: Visit http://flask-app.local to see your application.

4. Destroy the VM when finished:

   dockvirt down --name flask-app
   

Note: Do not run dockvirt or make with sudo. The tools request sudo only when needed and act on your real HOME.

Automatic Image Downloading

On the first run, dockvirt will automatically download the required operating system image:

• Ubuntu 22.04: ~/.dockvirt/images/jammy-server-cloudimg-amd64.img
• Fedora 38: ~/.dockvirt/images/Fedora-Cloud-Base-38-1.6.x86_64.qcow2

Images are cached locally, so subsequent runs will be much faster.

What’s happening in the background?

When you run dockvirt up, the tool:

1. Automatically downloads the Ubuntu 22.04 or Fedora 38 image (on first run)
2. Copies the Dockerfile, app.py, requirements.txt, and other application files to the VM
3. Creates a virtual machine with Docker and Caddy
4. Builds a Docker image with the Flask application inside the VM
5. Starts the application container with a reverse proxy
6. Configures access via the domain

Getting the VM IP

Use the local CLI from the repository venv to retrieve the VM IP:

../../.venv-3.13/bin/dockvirt ip --name flask-app

If you test HTTP via IP and use a reverse proxy (Caddy) inside the VM, include a Host header:

curl -H 'Host: flask-app.local' http://<ip>/

Networking: NAT vs Bridge (LAN)

By default, libvirt NAT (network=default) is used. To expose the VM directly in your LAN, create a bridge (e.g., br0) and run:

../../.venv-3.13/bin/dockvirt up --net bridge=br0

Persist per project by adding to .dockvirt:

net=bridge=br0

Example bridge creation (Fedora/NetworkManager):

```bash sudo nmcli con add type bridge ifname br0 con-name br0 sudo nmcli con add type bridge-slave ifname enp3s0 master br0 sudo nmcli con modify br0 ipv4.method auto ipv6.method auto sudo nmcli con up br0

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