Nginx Interview Questions

Nginx is a type of an open source web server which is especially used for reverse proxy, load balancer, mail proxy and for the HTTP cache. Nowadays NGINX software is most commonly used by various companies. NGINX can run on Linux, Mac OS X, Solaris, AIX, HP-UX, and the BSD variants.

The language in which the Nginx software is written is ‘C’ Language.

The following are the main tasks of the Nginx web server:

• The main task of the Nginx web server is to deploy dynamic HTTP content on a network using SCGI, Fast CGI handlers for scripts, WSGI application servers or Phusion passenger module.
• Nginx is also used to serve as a load balancer.

The official website of the Nginx web server is Nginx.org

The following are the differences between Nginx and Apache:

• Firstly, Nginx is an event-based web server and Apache is a process-based server.
• Nginx is best known for its speed and Apache is best known for its power.
• Nginx is the best when it comes to memory consumption and connection whereas Apache is not best in this category.
• In Nginx, a single thread is handling all of the requests whereas in Apache single thread handles a single request.
• Nginx is best when you want the load balancing. But Apache will refuse the new connection when traffic reaches the limit of the process.
• Apache provides lots of functionality as compared to Nginx.

The following are the types of versions of Nginx web server:

• Mainline - This version of Nginx contains latest features and bug fixes that are up to date. It is also reliable but it may contain some experimental modules.
• Stable- This version of Nginx doesn’t have the latest features but has critical bug fixes. A stable version is always recommended for the production servers.

A master processor in Nginx performs the privileged operations such as reading configuration and binding to ports.

A work process in Nginx actually does the whole processing of the requests.

Once the Nginx is started you can use the command to control or to stop it. The main command used in the Nginx web server is

Nginx –S signal

In the place of the signal, you can put the command that is being used to control the Nginx. The following are the command you can use in place of the signal:

• Stop – use this command if you want to fast shutdown
• Quit – you have to use this when you want to gracefully shutdown the Nginx.
• Reload – use this command when you want to see the configuration file
• Reopen – Reopen file is used for reopening of the file once again.

The sub status directives is mainly used to know all the current status of Nginx. You can know the current active connections, total connections that are being accepted and all the handled current number of read, write and wait connections.

A sub_filter directive in Nginx is a replacement string. It allows you to perform modifications by replacing specific string to another one. The updated version of Nginx allows you to use multiple sub_filter directives simultaneously. There are different sub_filter directives for different purposes like

• To set a string replacement

  Syntax: sub_filter string replacement

• To preserve the last-modified header

  Syntax: sub_filter_last_modified on | off;

  Default: sub_filter_last_modified off;

• To remove the header field with specific content

  Syntax: sub_filter_once on | off

  Default: sub_filter_once on;

• Indicate the place of each string either for replacing once or repeatedly

  Syntax: sub_filter_types mime-type .

  Default: sub_filter_types text/html;

It is always suggested not to use a third party sub filter module, it may be powerful but there can be a lot of bugs. Instead you csj use the standard sub filter for your needs.

The main purpose of the –s parameter is to run the executable files.

The following are the main controls used in the Nginx web server:

• Stop
• Quit
• Reopen
• Reload

CSK10 problem is being referred to the network socket that failed to handle a large number of clients at the same time.

If you want to start the Nginx server, then you have to go to/ etc/ Nginx / site enabled/ and if there is a default file, then you have to open a file called default.

Firstly, you have to select the Nginx module during the compile. Runtime selection of module is not being supported by the Nginx server.

A directive in NGINX is used to route the server where to look for a resource by including files and folders while matching a location block against a URL.