What are the best security practices when writing a Dockerfile and running containers?

The security of containerized applications begins at the Dockerfile creation stage and continues when configuring the runtime environment. By default, many processes inside containers run with root superuser privileges. This creates a serious vulnerability, because if the application is compromised, the attacker gains full control over the entire Linux kernel namespace and can attempt to break out of the isolated environment onto the host machine.

The first and most important security rule is to avoid using the root user by default. Inside the Dockerfile, you must create a non-privileged system user and switch to it using the user instruction before launching the application. You should also approach the choice of base images carefully, favoring official minimal builds or specialized images without unnecessary utilities, such as distroless.

To maintain a high level of infrastructure security, it is recommended to apply the following measures.

Following these simple rules allows you to significantly reduce the risks of data compromise and ensure compliance with modern information security standards when deploying a microservice architecture based on Docker.