Top 25+ Nginx Interview Questions and Answers

Nginx is a web server that can also act as a reverse proxy, load balancer, mail proxy, and HTTP cache. It was created by Igor Sysoev in 2002 and released as an open-source project in 2004. Nginx is known for its high performance, scalability, stability, and low resource consumption. It can handle millions of concurrent connections and serve static and dynamic content efficiently.  

Nginx software was written in C language. C is a low-level and powerful programming language that allows Nginx to have direct access to the system resources and optimise performance and memory usage.  

The main tasks of the Nginx web server are:  

a) To accept and process HTTP requests from clients 

b) To serve static files such as images, CSS, JavaScript, etc. 

c) To pass dynamic requests to upstream servers such as PHP, Python, Ruby, etc. 

d) To balance the load among multiple upstream servers 

e) To cache the responses from upstream servers 

f) To compress and encrypt the responses 

g) To rewrite and redirect the requests based on rules 

h) To log the requests and errors 

The official website of the Nginx web server is https://nginx.org/. You can find the latest news, documentation, downloads, and support information about Nginx on this website.  

Nginx and Apache are both popular web servers, but they have some differences in their architecture, performance, and features. Some of the main differences are:  

a) Nginx uses an event-driven and asynchronous model, while Apache uses a process-based and synchronous model. This means that Nginx can handle more concurrent connections and requests with less CPU and memory usage than Apache. 

b) Nginx is faster and more efficient at serving static files than Apache, while Apache has more features and modules for serving dynamic content than Nginx. 

c) Nginx has a simpler and more modular configuration file than Apache, which makes it easier to maintain and customise. 

There are two types of versions of the Nginx web server: stable and mainline. The stable version is the one that has been tested and verified for reliability and security. The mainline version is the one that has the latest features and bug fixes but may not be as stable or secure as the stable version. The stable version is recommended for production environments, while the mainline version is recommended for testing and development environments. 

The master processor in Nginx is responsible for reading and validating the configuration file, creating and managing the worker processes, and handling the signals and events. The master processor runs as a root user and does not process any requests. It only communicates with the worker processes through shared memory and sockets.  

The worker processor in Nginx is responsible for processing clients' requests. The worker processes run as a non-root user and do not communicate with each other. They only communicate with the master process and the upstream servers. The number of worker processes can be configured by the worker_processes directive in the configuration file. The optimal number of worker processes depends on the number of CPU cores and the expected load. 

The sub_status directives in Nginx are used to enable and configure Nginx's live activity monitoring. By setting the sub_status directive to on, Nginx will provide a web page that shows the current status of the server, such as the number of active connections, requests, and bytes transferred. The sub_status_zone directive is used to define the shared memory zone for storing the status information. The sub_status_allowed_ips directive is used to specify the IP addresses that are allowed to access the status page.  

The purpose of the –s with Nginx Server is to send a signal to the master process to perform a certain action. The possible signals are:  

1) stop: to stop the Nginx server immediately 

2) quit: to stop the Nginx server gracefully 

3) reload: to reload the configuration file 

4) reopen: to reopen the log files 

For example, to reload the configuration file, you can use the command:  

nginx -s reload  

Empower your IT support team with NGINX Training for optimised web server performance and enhanced solutions! 

The controls used in the Nginx web server are the directives and the blocks. The directives are the commands that specify the behaviour and parameters of the server. The directives are written in the form of name values. The blocks are the containers that group the directives according to their context and scope. The blocks are written in the form of name { ... }. The main types of blocks are:  

1) main: the global configuration of the server 

2) events: the configuration of the connection processing 

3) http: the configuration of the HTTP server 

4) server: the configuration of the virtual server 

5) location: the configuration of the request processing based on the URI 

6) upstream: the configuration of the upstream server group 

The C10K problem is the challenge of handling 10,000 concurrent connections on a single web server. Traditional web servers, such as Apache, use a process-based or thread-based model, which creates a new process or thread for each connection. This consumes a lot of system resources and limits the scalability and performance of the server 

To start the Nginx server through other ports, you need to change the listen directive in the server block of the configuration file. The listen directive specifies the port and the IP address that the server listens on. By default, the listen directive is set to 80, which is the standard port for HTTP. You can change it to any other port that is not occupied by another service. For example, to start the Nginx server on port 8080, you can use the following listen directive:  

listen 8080;  

You can add module to the Nginx server by compiling the module with the Nginx source code. Nginx does not support dynamic loading of modules, so you need to recompile the server with the module that you want to add. To do this, you need to download the Nginx source code and the module source code, and then use the --add-module option with the configure script. For example, to add the ngx_http_geoip_module, you can use the following command:  

./configure --add-module=/path/to/ngx_http_geoip_module  

Then, you need to run the make and make install commands to compile and install the server with the module.  

A directive in Nginx is a command that specifies the behaviour and parameters of the server. A directive consists of a name and a value, separated by a space, and ends with a semicolon. For example, the worker_processes directive sets the number of worker processes that the server uses:  

worker_processes 4;  

Some directives can have multiple values, separated by spaces. For example, the index directive sets the default file names that the server looks for when a directory is requested:  

index index.html index.htm;  

Some directives can have no value, which means they are either on or off. For example, the sub_status directive enables the live activity monitoring of the server:  

sub_status on;  

Expand your learning curve by signing up for our IT Support and Solution Training now! 

The advantage of using a reverse proxy server is that it can improve the performance, security, and reliability of the web application. A reverse proxy server is a server that sits between the client and the upstream server and acts as an intermediary. It can perform various functions, such as:  

1) Load balancing: it can distribute the requests among multiple upstream servers based on the availability and capacity of each server.  

2) Caching: it can store the responses from the upstream servers and serve them to the clients without contacting the upstream servers again, which reduces the network latency and bandwidth consumption 

3) Compression: it can compress the responses before sending them to the clients, which reduces the size of the data and improves the speed 

4) Encryption: it can encrypt the communication between the client and the server, which enhances the security and privacy of the data 

5) Authentication: it can verify the identity and credentials of the clients before allowing them to access the upstream servers, which prevents unauthorised access and attacks 

6) Logging: it can record the requests and responses for debugging and analysis purposes, which helps to monitor and optimise the performance and functionality of the web application 

To start Nginx through a different port other than 80, you need to change the listen directive in the server block of the configuration file. The listen directive specifies the port and the IP address that the server listens on. By default, the listen directive is set to 80, which is the standard port for HTTP. You can change it to any other port that is not occupied by another service. 

In Nginx, you can keep double slashes in URLs by using the merge_slashes directive in the http block of the configuration file. The merge_slashes directive determines whether Nginx should merge adjacent slashes in the request URI or not. By default, the merge_slashes directive is set to on, which means that Nginx will merge the double slashes into a single slash.   

The ngx_http_upstream_module is used for defining and configuring the upstream server groups that Nginx can proxy the requests to. The upstream server groups are defined by the upstream block in the http block of the configuration file. The upstream block consists of a name and a list of server directives that specify the IP address and the port of each upstream server.  

The upstream server groups can be referenced by the proxy_pass directive in the location block to pass the requests to the upstream servers. For example, to define an upstream server group named backend with two servers, you can use the following upstream block:  

upstream backend {   server 192.168.0.1:8080;   server 192.168.0.2:8080; }  

To pass the requests to the backend server group, you can use the following proxy_pass directive in the location block:  

location / {   proxy_pass http://backend; }  

The C10K problem is the challenge of handling 10,000 concurrent connections on a single web server. Traditional web servers, such as Apache, use a process-based or thread-based model, which creates a new process or thread for each connection. This consumes a lot of system resources and limits the scalability and performance of the server. 

Create, deploy and manage your server by signing up for our Introduction to Networking Training now! 

Nginx Server is a web server that can also act as a reverse proxy, load balancer, mail proxy, and HTTP cache. It was created by Igor Sysoev in 2002 and released as an open-source project in 2004. Nginx Server is known for its high performance, scalability, stability, and low resource consumption. It can handle millions of concurrent connections and serve static and dynamic content efficiently.  

Nginx is written in C language. C is a low-level and powerful programming language that allows Nginx to have direct access to the system resources and optimise performance and memory usage.  

The official website of Nginx is https://nginx.org/. You can find the latest news, documentation, downloads, and support information about Nginx on this website.  

Apache Web Server and Nginx are both popular web servers, but they have some differences in their architecture, performance, and features. Some of the main differences are:  

1) Apache Web Server uses a process-based or thread-based model, while Nginx uses an event-driven and asynchronous model. This means that Nginx can handle more concurrent connections and requests with less CPU and memory usage than Apache Web Server. 

2) Nginx is faster and more efficient at serving static files than Apache Web Server, while Apache Web Server has more features and modules for serving dynamic content than Nginx. 

3) Nginx has a simpler and more modular configuration file than Apache Web Server, which makes it easier to maintain and customise. 

4) Nginx has built-in support for reverse proxying, load balancing, and caching, while Apache Web Server requires additional modules or software for these functions. 

5) Nginx has better support for HTTP/2, WebSocket, and streaming protocols than Apache Web Server, while Apache Web Server has better support for .htaccess files and CGI scripts than Nginx. 

Some of the features of Nginx are:  

1) High performance and scalability: Nginx can handle millions of concurrent connections and requests with minimal CPU and memory usage, thanks to its event-driven and asynchronous architecture and non-blocking I/O mechanism. 

2) Versatility and flexibility: Nginx can serve as a web server, a reverse proxy, a load balancer, a mail proxy, and an HTTP cache, and can support various protocols, such as HTTP, HTTPS, HTTP/2, WebSocket, TCP, UDP, etc. 

3) Modularity and extensibility: Nginx has a modular design that allows users to add or remove modules according to their needs. Nginx also has a rich set of modules that provide various functions, such as compression, encryption, authentication, logging, rewriting, etc. 

4) Simplicity and reliability: Nginx has a simple and clear configuration file that is easy to read and write. Nginx also has a robust and stable code base that ensures the reliability and security of the server.