How should I prepare for a junior server admin role in three months?

Use the first month to turn your command line experience into administration practice. Set up a Linux virtual machine, manage users and permissions, configure a service, inspect its logs, and practice diagnosing why it won't start. Keep notes on what broke and how you fixed it.

In the second month, add Git and small Bash scripts for repetitive tasks. In the third, build a small server project and practice explaining its setup and troubleshooting. Pick one concrete task each week so you can see progress rather than just collecting tutorials.

For a more infrastructure-focused project, make a tiny web service that returns a success response. Containerize it with a Dockerfile, run it locally, then try a multistage build. After that, set up a GitHub workflow to build the image and push it to Docker Hub.

If the jobs you're targeting mention Kubernetes, try deploying the container with k3s, k3d, or MicroK8s. That gives you a sequence of things to learn, but one project alone isn't proof that you're ready for every server admin role.

Look at the actual junior roles you want before spending weeks on Kubernetes. Server administration and DevOps responsibilities vary by employer, and some jobs will care much more about Linux troubleshooting than a particular deployment tool. Use those job descriptions to decide what gets your limited study time.