LeashLeash

Deploy Docker

If a Dockerfile exists in your project root, Leash uses it directly instead of auto-detecting a framework. This gives you full control over the build process.

Detection

A Dockerfile in the project root takes priority over all other detection. Leash builds the image from your Dockerfile and deploys it.

Terminal

$ leash deploy

✓ Detected Dockerfile

✓ Building from Dockerfile...

✓ Image built and pushed

✓ Deployed successfully!

→ https://my-app-arvin.un.leash.build

When to Use a Dockerfile

  • You need system-level dependencies not covered by Nixpacks
  • You want multi-stage builds for smaller images
  • Your app uses a language or framework Leash doesn't auto-detect
  • You need precise control over the runtime environment

PORT Environment Variable

Important: expose the right port

Your container must listen on the port specified by the PORT environment variable (defaults to 8080). Use EXPOSE 8080 in your Dockerfile and read $PORT at runtime.

Example Dockerfile

A multi-stage Node.js Dockerfile that produces a small production image:

Dockerfile
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM node:20-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/package.json ./

EXPOSE 8080
CMD ["node", "dist/index.js"]