docker-images-image-size-and-security

Image Size and Security

When building container images, it’s essential to be aware of both image size and security. The size of the image affects the speed at which your containers are built and deployed. Smaller images lead to faster builds and reduced network overhead when downloading the image. Security is crucial because container images can contain vulnerabilities that could potentially put your applications at risk.

Reducing Image Size

Use an appropriate base image: Choose a smaller, more lightweight base image that includes only the necessary components for your application. For example, consider using the alpine variant of an official image, if available, as it’s typically much smaller in size.

FROM node:14-alpine

Run multiple commands in a single RUN statement: Each RUN statement creates a new layer in the image, which contributes to the image size. Combine multiple commands into a single RUN statement using && to minimize the number of layers and reduce the final image size.

RUN apt-get update && \
    apt-get install -y some-required-package

Remove unnecessary files in the same layer: When you install packages or add files during the image build process, remove temporary or unused files in the same layer to reduce the final image size.

RUN apt-get update && \
    apt-get install -y some-required-package && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

Use multi-stage builds: Use multi-stage builds to create smaller images. Multi-stage builds allow you to use multiple FROM statements in your Dockerfile. Each FROM statement creates a new stage in the build process. You can copy files from one stage to another using the COPY --from statement.

FROM node:14-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM node:14-alpine
WORKDIR /app
COPY --from=build /app/dist ./dist
COPY package*.json ./
RUN npm install --production
CMD ["npm", "start"]

Use .dockerignore file: Use a .dockerignore file to exclude unnecessary files from the build context that might cause cache invalidation and increase the final image size.

node_modules
npm-debug.log

Enhancing Security

Keep base images updated: Regularly update the base images you’re using in your Dockerfiles to ensure they include the latest security patches.
Avoid running containers as root: Always use a non-root user when running your containers to minimize potential risks. Create a user and switch to it before running your application.

RUN addgroup -g 1000 appuser && \
    adduser -u 1000 -G appuser -D appuser
USER appuser

Limit the scope of COPY or ADD instructions: Be specific about the files or directories you’re copying into the container image. Avoid using COPY . . as it may unintentionally include sensitive files.

COPY package*.json ./
COPY src/ src/

Scan images for vulnerabilities: Use tools like Anchore or Clair to scan your images for vulnerabilities and fix them before deployment.

By following these best practices, you’ll be able to build more efficient and secure container images, leading to improved performance and a reduced risk of vulnerabilities in your applications.

Visit the following resources to learn more:

docker-images-image-size-and-security

Contents

Image Size and Security

Reducing Image Size

Enhancing Security