# Practice Exam - Betriebssysteme und Netzwerke

## Exam Information

- **Duration:** 45 minutes
- **Tasks:** 5 problems to diagnose and fix
- **Allowed:** 1x A4 cheat sheet (front and back)

---

## Scenario

You are a system administrator for a company. Multiple services on the server have stopped working after a colleague made some changes. Your task is to diagnose and fix all issues.

---

## Task 1: Company Portal Unreachable

**Service:** http://company.local

**Problem:** The company portal website is not loading. Users report seeing an error page or the page won't load at all.

**Expected Result:** The website should display "Company Portal" with "Status: Online"

**Test Command:**
```bash
curl http://company.local
```

**Category:** Web Server Configuration

---

## Task 2: Online Shop Shows 403 Forbidden

**Service:** http://shop.local

**Problem:** The online shop returns a "403 Forbidden" error when accessed.

**Expected Result:** The website should display "Online Shop" with "Status: Online"

**Test Command:**
```bash
curl http://shop.local
```

**Category:** File System Permissions

---

## Task 3: API Returns 502 Bad Gateway

**Service:** http://api.local:8080

**Problem:** The REST API returns a "502 Bad Gateway" error instead of JSON data.

**Expected Result:** The API should return a JSON response with `"status": "success"`

**Test Command:**
```bash
curl http://api.local:8080
```

**Category:** Service Management (systemd)

---

## Task 4: Docker Application Unreachable

**Service:** http://localhost:8888

**Problem:** The Docker web application running on port 8888 is not accessible. The connection times out.

**Expected Result:** The page should display "Docker Application" running in a container.

**Test Command:**
```bash
curl http://localhost:8888
```

**Hint:** The Docker container itself is running correctly.

**Category:** Firewall (UFW)

---

## Task 5: Database Connection Refused

**Service:** MySQL Database

**Problem:** The web application cannot connect to the MySQL database. Connection attempts with the `webuser` account are being refused.

**Credentials:**
- Username: `webuser`
- Password: `WebPass123!`
- Database: `practicedb`

**Expected Result:** Should be able to connect and query the database.

**Test Command:**
```bash
mysql -u webuser -p'WebPass123!' practicedb -e "SELECT * FROM products;"
```

**Category:** Database Administration

---

## Verification

Run the verification script to check your progress:

```bash
sudo ./break_server.sh
# Then select option 7) Verify all services
```

Or test each service manually with the curl commands above.

---

## Diagnostic Commands Reference

| Tool | Purpose |
|------|---------|
| `systemctl status <service>` | Check service status |
| `systemctl start/restart <service>` | Start or restart service |
| `nginx -t` | Test nginx configuration |
| `journalctl -u <service>` | View service logs |
| `ufw status` | Check firewall rules |
| `ss -tulnp` | Show listening ports |
| `ls -la <path>` | Check file permissions |
| `docker ps` | List running containers |
| `cat /var/log/nginx/error.log` | View nginx error logs |

---

## Good Luck!

Remember to work systematically:
1. Identify the symptom
2. Check service status
3. Review configuration/logs
4. Apply the fix
5. Verify the solution

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*Practice Exam - Betriebssysteme und Netzwerke*