Capstone labs · Lesson 4 of 18 · 8 minutes

Capstone web config

Review and validate web server config.

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learner@clairos:~ $

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Your objectives

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1
Read site config
Run cat /etc/nginx/sites-available/learn.conf.
Hint & worked example
Read one or more files to standard output without editing their contents.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cat /etc/nginx/sites-available/learn.conf
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
2
Find CSP
Run grep Content-Security-Policy /etc/nginx/sites-available/learn.conf.
Hint & worked example
Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
grep Content-Security-Policy /etc/nginx/sites-available/learn.conf
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Validate nginx
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.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

cat: Read one or more files to standard output without editing their contents.
Reading a source file should precede changing it; avoid printing real secrets.
grep: Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
No matches is exit status 1, which is different from a malformed invocation.
nginx: Check the simulated configuration using nginx -t before changing service state.
This lab checks a limited configuration subset, not the complete Nginx parser.

Worked example and expected result

$ cat /etc/nginx/sites-available/learn.conf

server {
  listen 443 ssl;
  server_name learn.clairos.ai;
  root /srv/www;
  location ^~ /api/learn/ { proxy_pass http://127.0.0.1:8010; }
  location ^~ /api/ { return 404; }
  add_header Content-Security-Policy "default-src 'self'; connect-src 'self'" always;
  # training config only
}

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

$ grep Content-Security-Policy /etc/nginx/sites-available/learn.conf

  add_header Content-Security-Policy "default-src 'self'; connect-src 'self'" always;

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.

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 “Capstone web config”, which interpretation is safe?No matches is exit status 1, which is different from a malformed invocation.A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Capstone permission audit Try an incident drill

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