Containers are naturally ephemeral, meaning they vanish along with all their data once stopped or deleted. This is fine for stateless apps like simple web servers, but not ideal for databases, uploaded files, or logs, anything that must persist. That’s where Docker Volumes come to the rescue . They store data outside the container, ensuring…
Category: Docker
Fixing “Permission Denied” Errors in Containers
A common issue encountered while containerizing applications is when the app runs perfectly on a local machine but crashes inside a container with a “permission denied” error. This behavior often confuses engineers since the same steps work outside the container but fail within it. 🔍 Understanding the Root Cause The main reason behind this issue…
Fixing Port Accessibility Issues in Docker Containers
Sometimes an application inside a Docker container is running, but when accessed via localhost:<port>, nothing loads or it times out. This can be confusing because the container is running and port mapping has been configured, yet the application remains inaccessible from the host machine. Example Scenario Troubleshooting Steps There are multiple reasons this can happen….
Purpose of EXPOSE in a Dockerfile
If you’ve ever peeked into a Dockerfile, you might have come across a line like this: At first glance, it looks like it’s opening a port — but here’s the catch: it doesn’t actually open or publish anything to the outside world! 😮 Let’s unpack what it really does and why it’s still an important…
Why Docker Containers Exit Immediately After Starting
A frequently observed issue when working with Docker is that a container starts successfully but exits right away. Understanding why this happens helps ensure containers behave as expected and remain stable during runtime. Understanding the Behavior ⚙️ Docker containers are designed to run a single main process. Once that process finishes, the container automatically stops….
Why Code Changes May Not Reflect in a New Docker Image
One of the confusing situations while working with Docker occurs when a new image is built after code changes — yet those updates don’t appear in the container. This often leads to frustration between developers and DevOps engineers during testing or release cycles. The Scenario 💡 Consider a case where a developer is working on…