Challenges
Focused, hands-on DevOps problems based on real production incidents. Each one drops you into a broken server with a simulated terminal, and comes with hints, an automated solution check and a walkthrough explaining the fix.
10 challenges
Linux
Disks, processes, services and permissions: your first on-call week.
Challenge on Linux
Disk full on prod
by @loopedin.daily
Deploys fail with 'No space left on device'. Find what's eating / and free it without stopping the API.
#df#du#logs#truncate
Easy~5 minSolveChallenge on Linux
"I deleted it, still 100%"
by @loopedin.daily
A teammate rm'd the giant log but df hasn't moved. Find where the space went and get it back.
#lsof#df#deleted-files#systemctl
Medium~8 minSolveChallenge on Linux
Backup cron silently failing
by @loopedin.daily
The nightly DB backup hasn't produced a file in 9 days and nobody noticed. Make the cron job work again.
#cron#chmod#syslog#bash
Easy~6 minSolve
Networking
Ports, reverse proxies, DNS and TLS between the user and your process.
Challenge on Networking
Nginx returns 502
by @loopedin.daily
Every request gets 502 Bad Gateway. Nginx is up, so who isn't? Find the dead upstream and bring it back.
#nginx#curl#journalctl#systemctl
Easy~5 minSolveChallenge on Networking
DNS resolves to the wrong IP
by @loopedin.daily
DNS was migrated yesterday and dig shows the new IP, yet the app still talks to the old server. Why?
#dig#getent#hosts#dns
Medium~7 minSolveChallenge on Networking
Address already in use :8080
by @loopedin.daily
After the deploy the service won't start: EADDRINUSE on :8080. Something is squatting on the port.
#ss#lsof#kill#systemctl
Easy~5 minSolve
Containers
Docker containers that won't start, can't connect or eat the disk.
Kubernetes
Pods that crash, can't pull, or never get traffic.
Challenge on Kubernetes
ImagePullBackOff
by @loopedin.daily
The new release never starts: pods sit in ImagePullBackOff. Find out why and ship the right image.
#kubectl#describe#set-image#registry
Easy~5 minSolveChallenge on Kubernetes
Pod in CrashLoopBackOff
by @loopedin.daily
The API pod restarts every 30 seconds. The current logs are empty. Find the crash reason and fix the config.
#kubectl#logs#configmap#rollout
Medium~8 minSolve
Observability
Turn raw logs into answers with a few pipes.
Advanced challenges
Interview-grade incidents: OOMKilled pods, stuck rollouts, leaked secrets, Terraform locks.
8 advanced incidents, unlocked with Pro
New ones added every week. One payment, yours for life.
Pro · coming soon