Capstone labs · Lesson 17 of 18 · 8 minutes

Capstone multi-signal outage

Correlate service, config, journal, listener, and capacity evidence for an outage.

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Your objectives

Hints are always available. Wrong turns never cost XP.

1
Check service state
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 the configuration
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 recent service evidence
Run journalctl -u nginx -n 2.
Hint & worked example
Read the training journal by unit or a bounded line window.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
journalctl -u nginx -n 2
```
Remember: A relevant unit and time range are more useful than an unfiltered wall of logs.
4
Check listeners
Run ss -tulpn.
Hint & worked example
Inspect simulated listening sockets and connection information.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ss -tulpn
```
Remember: A listening socket is not proof of correct application responses or external reachability.
5
Check capacity
Run df -h.
Hint & worked example
Inspect the virtual filesystem capacity report. Real systems can run out of space or inodes independently.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
df -h
```
Remember: Available space is a snapshot, not a guarantee that a later write will succeed.

Understand the pattern

Running an end-to-end outage investigation helps operators explain what they know before they change anything.

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.
journalctl: Read the training journal by unit or a bounded line window.
A relevant unit and time range are more useful than an unfiltered wall of logs.
ss: Inspect simulated listening sockets and connection information.
A listening socket is not proof of correct application responses or external reachability.
df: Inspect the virtual filesystem capacity report. Real systems can run out of space or inodes independently.
Available space is a snapshot, not a guarantee that a later write will succeed.

Worked example and expected result

$ systemctl status nginx

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