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Common Docker Misconfigurations and How to Prevent Them
Govardhana M K
September 30, 2025
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TechOps Examples
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🧠 Use Case
Common Docker Misconfigurations and How to Prevent Them
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🧠 USE CASE
Common Docker Misconfigurations and How to Prevent Them
DevOps engineers often find themselves chasing problems in Docker that turn out to be simple misconfigurations. A missing limit, an overlooked flag, or an insecure default can lead to wasted hours in debugging, performance degradation, or even security incidents. Most of these challenges are avoidable if the basics are set right from the start.
It is worth taking a quick look at how Docker works before we get into the core of today's topic.
A typical Docker workflow starts with the client running commands like docker build, docker pull, or docker run. These commands are sent to the Docker daemon on the host. The daemon fetches images from a registry or builds them locally, stores them as reusable artifacts, and then launches containers from those images. Containers are the isolated environments where applications actually run.
Typical Misconfigurations You Should Avoid:
1. Running Docker container in rootless mode
By default, Docker containers run as the root user, which increases the risk of privilege escalation if the container is compromised. A safer practice is to create and use a non root user inside the container.
2. Using tagged minimal base images and multistage builds
Using large untagged images leads to bloated containers and unpredictable builds. A better approach is to use versioned tags and multistage builds. Here, dependencies are installed in a builder image, and only the required artifacts are copied into a lightweight runtime image.
3. Using COPY command with specific parameters
Using a broad COPY . . can unintentionally include unnecessary files such as configs, build artifacts, or secrets. It makes images larger and riskier. Instead, copy only the required files or directories explicitly, like COPY target/app.jar /app.
4. Update and install packages in the same RUN instruction
Splitting updates and package installations across multiple RUN layers leads to larger image sizes and cache inconsistencies. Combining them in a single RUN reduces layers, keeps images cleaner, and ensures package versions remain consistent during builds.
5. Removing unnecessary dependencies
Package managers often install extra packages by default, which makes images larger and more complex. Installing only what is strictly required keeps the image lightweight, improves maintainability, and reduces the potential attack surface.
Takeaway
Write Dockerfiles with least privilege, minimal images, explicit copies, single layer installs, and trimmed dependencies to achieve smaller, safer, and more predictable containers.
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