Challenge, Easy,  on  Kubernetes

Configure a Memory-Backed emptyDir Volume with a Size Limit

Omkar Shelke
by  Omkar Shelke

Scenario

A Deployment named session-store is running in namespace cherry. The Pods use a volume named cache-volume of type emptyDir — currently disk-backed with no size limit.

The application needs faster I/O, so the team wants to switch the volume to memory-backed storage using tmpfs. However, a memory-backed emptyDir without a size limit can consume all available node RAM and trigger the OOM killer.

The manifest is on the dev-machine at:

/home/laborant/session-store.yaml

Task

Update cache-volume in the manifest to use memory-backed storage with a size limit:

  • medium: Memory
  • sizeLimit: 256Mi

Apply the updated manifest.

Hint

medium: Memory mounts the volume as tmpfs — it uses RAM instead of disk.Reads and writes are significantly faster than disk-backed storage, but the data is lost when the Pod restarts. Without sizeLimit, the volume can grow until the node runs out of memory — so always cap it.

Then apply:

kubectl apply -f /home/laborant/session-store.yaml

See the official docs: Volumes — emptyDir

Test Cases

How to Author Challenges on iximiuz Labs

Instead of providing a subpar online editing experience, iximiuz Labs offers a helper CLI tool called labctl, allowing you to use your favorite text editor (or a full-featured IDE) to write content from the comfort of your local machine.

Install labctl CLI

curl -sf https://labs.iximiuz.com/cli/install.sh | sh

This will download and install the latest version of the labctl CLI. You only need to do this once per workstation.

Authorize labctl

labctl auth login

This will open a browser window asking you to authorize labctl to access your account. You need to do it after a fresh install of labctl and repeat it whenever the auth session expires.

Pull challenge content

labctl content pull challenge configure-memory-backed-emptydir-volume-with-a-size-limit-3b7688a0

This will create a local copy of the challenge content in a directory named configure-memory-backed-emptydir-volume-with-a-size-limit-3b7688a0. You only need to do this once per challenge.

Stream your changes

labctl content push -fw challenge configure-memory-backed-emptydir-volume-with-a-size-limit-3b7688a0

Run this command in a separate terminal to continuously upload your changes to the server while editing the challenge in your favorite text editor or IDE.

You can also use labctl to create, list, and delete your content. Learn more about the available commands: labctl content --help

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