UNIX related tutorial/FAQ

How to hide Nginx version on Linux and Unix

last updated June 23, 2020 in Linux, Nginx, Security, Security Through Obscurity, UNIX

By default, the Nginx version displayed when you query HTTP headers or error generated by the Nginx server. This quick guide explains how to hide or remove the Nginx version on Linux or Unix server without restarting the system.

Nginx restore real IP address when behind a reverse proxy

last updated May 7, 2020 in BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, Nginx, Suse, UNIX

My Nginx web server is behind a reverse proxy server. How do I restore the original and real IP address of my client/visitors when behind a reverse proxy server such as AWS Cloudfront, Fastly, Cloudflare CDN/WAF?

How to forcefully renew Let’s Encrypt certificate

last updated July 6, 2020 in CentOS, Cryptography, Debian / Ubuntu, FreeBSD, Linux, RedHat and Friends, Suse, UNIX

How do I forcefully renew the Letsencrypt certificate on an Ubuntu, Debian, CentOS, RHEL, Fedora, or FreeBSD Unix systems?

How to sed remove last character from each line

last updated April 27, 2020 in BASH Shell, CentOS, csh, Debian / Ubuntu, FreeBSD, KSH Shell, Linux, Suse, UNIX

I need to remove the last character from a line and shell variable such as “${_allowed_ips}“. For example, each line is as follows in my file:
foo,
bar,
demo,
I need output as follows:
foo
bar
demo.
How can I use sed to delete the last character?

How to save terminal output to a file under Linux/Unix

last updated April 19, 2020 in BASH Shell, KSH Shell, Linux, UNIX

How do I save the terminal output to a file when using BASH/KSH/CSH/TCSH under Linux, macOS, *BSD or Unix-like operating systems?

Unix Basics Quiz

last updated March 22, 2020 in UNIX

Let us test your basic knowledge of Unix systems, including commands.

Linux Quiz

last updated March 10, 2020 in BASH Shell, Linux, UNIX

Let us test your basic knowledge of Linux systems, including commands.

nixCraft