UNIX / Linux
Learn the shell, read logs, manage files, and diagnose services.
$ grep denied auth.log | tail -n 30 / 360 complete
Learn by operating
the system.
Run the command. Read the evidence. Solve the problem.
Hands-on UNIX, Web, and AI Operations practice in your browser. No setup, no virtual machine, and no risk to your real system.
No account required. Create a free account only when you want to keep progress between sessions.
Your first commandTry
pwd, then ls.learner@clairos:~ $
↑ history · Tab complete · Ctrl+C cancel · Esc, Tab to leaveExit 0
A real interaction with a simulated filesystem. Nothing runs on your computer.
01Understand the task
Learn the concept, not just a command to copy.
02Work the problem
Real state, useful failures, and a reset whenever you need it.
03Prove the skill
Run it, explain it, then apply it to a new context.
Choose your field.
Three active tracks. 660 lessons. A place to begin—and a long way to go.
Web foundations
Build meaningful HTML, responsive CSS, and understandable JavaScript patterns.
<button type="button">Start</button>0 / 120 complete
AI Operations
Inspect models, retrieval, evaluations, deployment, and incident evidence.
$ jq .failing_dependency incident.json0 / 180 complete
The system is broken.
What do you check first?
Recover a stopped service. Restore a configuration. Investigate a log. Earn mastery by fixing the condition—not by typing a secret sequence.
Open the incident deskEight replayable drills with synthetic evidence. No racing the clock.
INCIDENT 01The site is down
$ curl http://localhost/
curl: (7) Connection refused
$ systemctl status nginx
Active: inactiveFind the cause. Make a careful change. Verify the recovery.
Progress you can point to.
Build XP, streaks, missions, three-part mastery, and recovery badges. Anonymous progress lasts for this session; a free account keeps synced lesson progress between sessions.
See my progress0lessons completed
0lessons mastered
A fresh problem. A useful habit.
Today's practice incident: The site is down.
Training, not a toy production server.
The terminal has a bounded Bash-like command language and virtual Linux state. Some administration tools use fixed fixtures. Web previews render an inert HTML/CSS subset; JavaScript is checked, not executed. AI Ops cases use fictional data, not live model calls.
Read exactly what the labs simulate