This quiz is part of the DevOpsTheHardWay course.

Please answer the quiz and click the "Test" button at the bottom right.

Webservers - Nginx - self-check questions

Question 1

Server administrator shuts down a Nginx server while allow the webserver to serve the remaining processes requests (graceful termination). Which command(s) did she use?

nginx -s stop
nginx -s quit
nginx -s reload
kill -s QUIT $(cat /var/run/nginx.pid)
nginx -s reopen

Question 2

Server administrator made some changes to the Nginx main configuration file (/etc/nginx/nginx.conf). Then performed sudo systemctl restart nginx. Choose the correct sentence(s).

The entire service has been restarted. Client's connection to the server might get dropped.
The Nginx service reloads configurations without stopping the server.
On syntax error, the server would not recover after restarted.
That method, not only the master process is being restarted, but also the workers.

Question 3

Server administrator made some changes to the Nginx main configuration file (/etc/nginx/nginx.conf). Then performed sudo nginx -s reload. Choose the correct sentence(s).

The entire service has been restarted. Client's connection to the server might get dropped.
The Nginx service reloads configurations without stopping the server.
On syntax error, the server would not recover after restarted.
That method, not only the master process is being restarted, but also the workers.

Question 4

A Nginx server is running on a VM with 4 CPUs. How many workers it is advisable to be run?

1
4
8
There is no any thumb rule.

Given the below output of Nginx service status:

● nginx.service - nginx - high performance web server
     Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
     Active: active (running) since Fri 2022-04-01 09:29:38 UTC; 29min ago
       Docs: https://nginx.org/en/docs/
    Process: 440 ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx-custom.conf (code=exited, status=0/SUCCESS)
   Main PID: 479 (nginx)
      Tasks: 3 (limit: 1111)
     Memory: 4.1M
        CPU: 15ms
     CGroup: /system.slice/nginx.service
             ├─479 "nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx-custom.conf"
             ├─480 "nginx: worker process" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""
             └─481 "nginx: worker process" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""

Answer the below 2 questions.

Question 5

Which of the following config files the server admin should edit in order to change the server's configurations:

/etc/nginx/nginx.conf
/etc/nginx/conf.d/default.conf
/etc/nginx/nginx-custom.conf
/var/run/nginx/nginx.conf
None of the above

Question 6

How many workers are currently running ?

Question 7

A Nginx server with default configuration. Given the below output of netstat -tuna command executed from the server's machine:

myuser@hostname:~$ netstat -tuna
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 127.0.0.1:3031          0.0.0.0:*               LISTEN     
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 172.31.46.24:80         93.172.114.143:47878    ESTABLISHED
tcp        0      0 127.0.0.1:3031          127.0.0.1:47792         TIME_WAIT  
tcp        0      0 127.0.0.1:47776         127.0.0.1:3031          TIME_WAIT  
tcp        0      0 127.0.0.1:3031          127.0.0.1:47788         TIME_WAIT    
tcp        0      0 172.31.46.24:80         14.101.201.16:47850    ESTABLISHED
tcp        0      0 172.31.46.24:80         33.9.115.215:47864    ESTABLISHED
tcp        0      0 127.0.0.1:3031          127.0.0.1:47760         TIME_WAIT

How many clients are currently hold an open socket connection with the server?

1
2
3
4
None of the above

Question 8

Given the below reverse proxy server configurations:

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://localhost:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

And given a client visits http://example.com/:

The client will be redirected to http://localhost:8000.
The client will be answered with Server not found since there is not running server under localhost:8000 on his local machine.
The client is not aware of http://localhost:8000.
The client URI is invalid.

Question 9

Given a Nginx server with the default configuration. What happens when a client performs an HTTP request with the header Accept: audio/wav?

Hint: Take a look on where /etc/nginx/nginx.conf includes the /etc/nginx/mime.types file. What does it do?

Nginx will return a 405 Not Acceptable.
Nginx will return a 406 Not Acceptable.
Nginx will return a 404 Not Found.
Nginx will return a 405 Bad request.

Question 10

Given the below 3 location directives:

location / {
    ...
}

location /images/ {
    ...
}

location /images/profiles/ {
    ...
}

Which of them will serve an HTTP GET request with URI: /images/123.png?

/
/images/
/images/profiles/
None of them

Given the below 3 location directives:

location / {
    ...
}

location /images/ {
    if ($request_method = POST) {
        return 400
    }
}

location location ~* ^/users/([0-9]+)/ {
    ...
}

Answer the below 4 questions.

Tip: Use regex101. Copy te expression ^/users/([0-9]+)/ and test some string examples.

Question 11

Which of them will serve an HTTP POST request with URI: /images/123.png?

/
/images/
^/users/([0-9]+)/
None of them

Question 12

Which of them will serve an HTTP GET request with URI: /images/users/123?

/
/images/
^/users/([0-9]+)/
None of them

Question 13

Which of them will serve an HTTP GET request with URI: /users/1?

/
/images/
^/users/([0-9]+)/
None of them

Question 14

Which of them will serve an HTTP GET request with URI: /users/?

/
/images/
^/users/([0-9]+)/
None of them

Question 15

Given the below 2 different server directives:

Version 1:

server {
    listen      80;
    server_name example.org www.example.org;
    ...
}

server {
    listen      80;
    server_name example.net www.example.net;
    ...
}

Version 2:

server {
    listen      80;
    server_name example.net www.example.net;
    ...
}

server {
    listen      80;
    server_name example.org www.example.org;
    ...
}

You are told that the machine's IP is 112.57.8.0. You open your local browser, type 112.57.8.0 and hit the Enter key.

The first server directive will serve the request, in both versions.
Both versions will serve example.org as .org is prior to .net in TLD level.
The request will not be served at all, an 201 status code is returned.
None of the above.

Question 16

Given the below reverse proxy configuration:

server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://localhost:8080;
    }
}

If a client sends an HTTP request to a web application (Flask) that is behind a reverse proxy (Nginx), which IP address will the web application see as the source of the request?

Nginx machine's IP
The client's IP
localhost
None of the above

Question 17

An uWSGI server is running the configuration under simple_flask_webserver/uwsgi.ini. Server administrator wants to inspect the socket that the uWSGI server is listening on:

myuser@hostname:~$ netstat -tuna
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 127.0.0.1:3031          0.0.0.0:*               LISTEN     
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN                        
tcp        0      0 127.0.0.1:3031          127.0.0.1:51054         TIME_WAIT  
tcp6       0      0 :::22                   :::*                    LISTEN

How could the uWSGI server accepts requests from clients, if the only socket it is listening 127.0.0.1:3031 (which means accepting connection from 127.0.0.1 only)?

The web application is not accessible that way.
The web application is accessible only for internal usage.
The uWSGI server only needs to listen for requests coming from the reverse proxy.
None of the above