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Reach a Distroless Container's Debug Endpoint From a Sidecar Container
A distroless container serves a debug interface on its own loopback address. Can you reach this debug endpoint using nothing but standard Docker commands?
Challenges
Focused, hands-on DevOps and server-side problems with hints, feedback, and automated solution checks.
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Run the Application's Test Suite in a Container Without Network Access
You are containerizing the dev workflows of a legacy Python service and you need to find out which external services its test suite talks to. Can you think of an easy way to do it?
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Turn Off a Feature Flag in a Production Redis Server Using a Local Containerized redis-cli
Ad-hoc containers are a handy way to run command-line tools without installing them on the host. Use one to access a production Redis server and turn off a feature flag. But beware of the gotcha: the production server can only be tunneled to the localhost.
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Docker 101: List Docker Networks and Inspect the Default Bridge
Explore the container networks of a freshly installed Docker host: find the default network, its subnet and gateway, and the Linux interface behind it.
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Docker 101: Publish All Exposed Ports on Random Host Ports to Avoid Port Conflicts
Can you get several builds of an app running side by side without port conflicts, so you can test them simultaneously?
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Docker 101: Publish a Redis Container Port on the Private Network Only
A common setup for small deployments: two servers (VM or bare-metal), each with a public and a private IP. The app listens on the public port but wants to talk to Redis over the private network. Can you set it up?
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Docker 101: Reach a Container Without Publishing a Port
Practice accessing a containerized service directly from the Docker host using its IP address.
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Docker 101: Publish a PostgreSQL Container Port on Localhost Only
Learn how to keep a database available to an app running on your workstation without exposing its port to other machines on the network.
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Docker 101: Publish a Container Port to Access the App from the Host
A web app is listening inside a container, but the browser can't reach its IP address. Recreate the container so the app is available on port 80 of the Docker host.
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Debug a Go Container Image That Fails to Start After a Recent Change
A Go service that has always been shipped as a static binary in a scratch-y image suddenly fails to start in a container, while the local build works as before. Find what recent changes caused it and fix the image without reverting them.