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Edit a File in a Running Kubernetes Pod: a Non-Root Container Case
Learn how to edit a file in a running Kubernetes Pod when the container's user has no write access to it.
Challenges
Focused, hands-on DevOps and server-side problems with hints, feedback, and automated solution checks.
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Edit a File in a Running Kubernetes Pod: a Distroless Container Case
Learn how to edit a file in a distroless container that runs as a non-root user in a Kubernetes namespace that enforces the baseline Pod Security Standard.
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Connect a Container to a Service Bound to Localhost on the Docker Host
Learn how to access a service bound to localhost of the Docker host from a bridge-networked container, without exposing the service to the local network or disabling network isolation.
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Connect a Container to a Service Running on the Docker Host
Learn how to access services running on the Docker host from a bridge-networked container, without hardcoding host IP addresses or disabling network isolation.
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Intercept and Analyze Encrypted Traffic of a Suspicious Container
Play a security researcher: identify the hosts a black-box container keeps making encrypted HTTPS calls to, route them through a MITM proxy, fake the certificate, and see what the container sends over the network.
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Redirect a Container's Requests Without Modifying the App
Sometimes you need an app to talk to a different backend, but its configuration is unknown or the destination address is hard-coded. Practice overriding hostname resolution for a single Docker container to redirect its requests without modifying the app or rebuilding its image.
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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?
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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.