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World L2: Keys & Staff · Boss challenge

The service that won't start

You will learn: to bring a broken web server back on your own: status, logs, fix, test, start.

Checked with Linux (Debian 13) on 1 Nov 2026

The problem

Boss: Monday, 8 am. Customers say the menu site is down. You try curl -sS localhost and get curl: (7) Failed to connect to localhost port 80 after 0 ms: Could not connect to server. Where do you look first?

Try it

Step 1: ask the shift manager if nginx is working. Then read its diary.

You are hereyou@kedai:~$

Folder ~

Empty folder

+ 3 hidden (ls -a)

Services

  • cronrunningstarts at boot
  • sshrunningstarts at boot
  • nginxfailedstarts at boot

Phone lines (network) Address 10.0.0.5

Listening ports

  • :22 sshd

Check

Step 2: tap the line that names the real problem.

0 of 1 found

Try it

Step 3: fix the typo, then test the settings: sudo sed -i 's/lisen/listen/' /etc/nginx/sites-available/default, then sudo nginx -t.

You are hereyou@kedai:~$

Folder ~

Empty folder

+ 3 hidden (ls -a)

Services

  • cronrunningstarts at boot
  • sshrunningstarts at boot
  • nginxfailedstarts at boot

Phone lines (network) Address 10.0.0.5

Listening ports

  • :22 sshd

Predict

nginx -t says test is successful. Is the menu site back now?

Try it

Step 4: the settings are fixed. Start nginx, then check the page like a customer would.

You are hereyou@kedai:~$

Folder ~

Empty folder

+ 3 hidden (ls -a)

Services

  • cronrunningstarts at boot
  • sshrunningstarts at boot
  • nginxfailedstarts at boot

Phone lines (network) Address 10.0.0.5

Listening ports

  • :22 sshd

Check

Write the “won’t start” ladder for the next person on shift.

First step at the top. Put these in order. Use the arrows, or drag.

  • sudo journalctl -u: why did it stop?
  • systemctl is-active or status: what does systemd say?
  • curl: is it really down?
  • Fix the file, then test it (nginx -t)
  • sudo systemctl start, then curl again

You did it!

You can now bring a broken service back on your own.

Go deeper (optional)

The same ladder works for any service: ssh, cron, a database. Many programs have their own test, like nginx -t. Fixed it? sudo systemctl enable nginx makes sure it also comes back after a reboot.

Real rep (optional), only on a throwaway VM with nginx installed:

Real mission

  1. sudo sed -i 's/listen 80/lisen 80/' /etc/nginx/sites-available/default
  2. sudo systemctl restart nginx
  3. sudo journalctl -u nginx -n 5
  4. sudo sed -i 's/lisen 80/listen 80/' /etc/nginx/sites-available/default
  5. sudo nginx -t && sudo systemctl restart nginx

0 of 5 steps done · Your ticks are saved.