CentOS related tutorial/FAQ

How to check open ports in Linux using the CLI

last updated July 22, 2019 in CentOS, Debian / Ubuntu, Linux, Networking, RedHat and Friends, Security, Suse

I need to list all open ports in Linux cloud server. How do I check open ports in Linux using the CLI? Can you give me the command to check open ports in Linux operating system?

Disable SELinux on CentOS 7 / RHEL 7 / Fedora Linux

last updated July 18, 2019 in CentOS, Linux, RedHat and Friends, SELinux

I need to disable SELinux on CentOS 7. How can I disable SELinux from the command line over ssh based session?

How do I force delete a directory in Linux?

last updated July 5, 2019 in BASH Shell, CentOS, Debian / Ubuntu, Linux, RedHat and Friends, Suse

I am trying to delete a directory in Linux using the rmdir dir1 command. But, I am getting an error that read as follows:
rmdir: failed to remove `dir1': Directory not empty
How do I force remove and delete a directory in Linux?

How to determine number of CPUs on Linux using command line

last updated June 7, 2019 in CentOS, Debian / Ubuntu, Hardware, Linux, RedHat and Friends, Suse

I am a new Linux system admin. How do I obtain the number of CPUs and cores in the Linux system from the command line? How do I determine the number of CPUs on Linux?

Use oathtool Linux command line for 2 step verification (2FA)

last updated July 29, 2019 in CentOS, Debian / Ubuntu, Linux, RedHat and Friends, Security, Suse

I do not wish to use Google Authenticator or Authy app that generates 2 step verification (2FA) codes on my iOS/Android phone. Is there any way I can produce 2FA codes from Linux command line for popular sites such as Gmail, Twitter, Facebook, Amazon and more?

Linux bash exit status and how to set exit status in bash

last updated March 7, 2019 in BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, Suse, UNIX

Can you explain bash exit status code? How do I set bash exit status in my Linux shell scripts?

How to find Intel NUC BIOS version and model on Linux

last updated January 26, 2019 in BASH Shell, CentOS, Debian / Ubuntu, Hardware, Linux, RedHat and Friends, Suse

I installed Linux on Intel NUC. I need to find Intel NUC BIOS version. How do I find out BIOS version, date, and model name of my Intel NUC using Linux command-line options?

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