Troubleshooting · Lesson 11 of 26 · 8 minutes

Incident website down

Triage a simulated website outage from service, config, and logs.

Open the lab Course map

Mastery 0/3Run itExplain itApply it

learner@clairos:~ $

↑ history · Tab complete · Ctrl+C cancel · Esc, Tab to leaveExit 0

Your objectives

Hints are always available. Wrong turns never cost XP.

1
Check nginx
Run systemctl status nginx.
Hint & worked example
Inspect or change a simulated systemd service. Status, active state, and unit configuration reveal different evidence.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
systemctl status nginx
```
Remember: A service can be active while an application endpoint is unhealthy; verify both layers.
2
Validate config
Run nginx -t.
Hint & worked example
Check the simulated configuration using nginx -t before changing service state.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
nginx -t
```
Remember: This lab checks a limited configuration subset, not the complete Nginx parser.
3
Read nginx errors
Run tail -n 2 /var/log/nginx-error.log.
Hint & worked example
Show the end of an input; -n selects the number of lines.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
tail -n 2 /var/log/nginx-error.log
```
Remember: This browser lab snapshots output; it does not keep a live tail -f stream.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

systemctl: Inspect or change a simulated systemd service. Status, active state, and unit configuration reveal different evidence.
A service can be active while an application endpoint is unhealthy; verify both layers.
nginx: Check the simulated configuration using nginx -t before changing service state.
This lab checks a limited configuration subset, not the complete Nginx parser.
tail: Show the end of an input; -n selects the number of lines.
This browser lab snapshots output; it does not keep a live tail -f stream.

Worked example and expected result

$ systemctl status nginx

nginx.service - simulated nginx
   Loaded: loaded
   Active: active
   Notes: serving the simulated static learn site

Exit status: 0. The command completed successfully in the training fixture.

$ nginx -t

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

Exit status: 0. The command completed successfully in the training fixture.

$ tail -n 2 /var/log/nginx-error.log

May 26 08:10:01 [notice] nginx: using fake static configuration
May 26 08:20:05 [warn] nginx: /api/test returned 404 by design

Exit status: 0. The command completed successfully in the training fixture.

Try a variation

Repeat this workflow in the sandbox with a different scratch filename. Keep the system fixtures unchanged and compare the observed output with your expectation before moving on.

Explain it

In “Incident website down”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.This lab checks a limited configuration subset, not the complete Nginx parser.

Apply it elsewhere

Before adapting the nginx workflow from “Incident website down” to another server, what should you do?Skip output inspection whenever the command is familiar.Confirm the current directory, target identity, permissions, and the installed command behavior first.Paste the training paths unchanged into production.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Incident disk filling Try an incident drill

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