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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.
Challenges
Focused, hands-on DevOps and server-side problems with hints, feedback, and automated solution checks.
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Harden a Django GraphQL API: Five Classic Flaws
by Adam Leskis
A stock Django + Strawberry GraphQL service ships with five common weaknesses. Probe each one from the terminal, fix it in the real project, and watch the lab confirm the remediation against the live endpoint.
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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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Safe Node Drain With a Disruption Budget
by Omkar Shelke
node-01 is due for maintenance, and it hosts two of the three checkout-api replicas. Add a PodDisruptionBudget so the drain can never take checkout below two available replicas, then drain the node.
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Troubleshoot an Ingress That Returns 404 Not Found
by Omkar Shelke
An nginx Deployment runs fine, but its address returns an error. Trace the path from the Ingress to the Pod and fix the manifests.
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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 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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Node Is Ready, but Pods Won't Schedule
by Omkar Shelke
node-02 is back from a kernel upgrade but still shows Ready,SchedulingDisabled, and the Pods that can only run on it are stuck in Pending. Bring the node back into service and get the workload running, without touching the workload itself.
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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.