nixCraft Linux & Unix Sysadmin/DevOps Tutorial Newsletter

[nixCraft]

** Welcome to nixCraft Linux/Unix newsletter for Friday, 8 April 2023. I hope you will enjoy this version of the newsletter.

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• nvtop – Awesome Linux task monitor for NVIDIA, AMD & Intel GPUs
  The nvtop command is an excellent task monitor for Linux users for NVIDIA, AMD and Intel GPUs (Graphics Processing Units). It is just like your top command or htop command and efficiently handles multiple GPUs in your system and shows details about them in a htop format. Let us see how to install the nvtop command on your Linux distro and monitor GPU tasks.
  
• How to skip ChatGPT from WireGuard or OpenVPN on Linux
  ChatGPT (short for Chat Generative Pre-trained Transformer) is a chatbot by OpenAI. It provides answers to your queries using learning techniques based on AI/ML. Unfortunately, ChatGPT deny access when connected via VPN (Virtual Private Network) such as WireGuard or OpenVPN. Let us see how to skip the ChatGPT domain from WireGuard or OpenVPN access while you can access corporate resources behind VPN.
  
• How To Set Up SSH Keys With YubiKey as two-factor authentication (U2F/FIDO2)
  All Linux and Unix servers are managed manually or by automation tools such as Ansible using ssh. For example, say you have a server at Linode or AWS. Then you copy your public ssh key to a remote cloud server. Once copied, you can now login to those servers without a password as long as ssh keys are matched. It is the best practice. Unfortunately, you are not protecting ssh keys stored on a local desktop or dev machine at $HOME/.ssh/ directory. If your keys are stolen, an attacker can get access to all of your cloud servers, including backup servers. To avoid this mess, we can protect our ssh keys stored on local dev/desktop machines using physical security keys such as YubiKey.
  
• How to tell ssh client to ignore ssh config file
  I have a tutorial that explains the basics of the SSH client configuration file and some of the most common configuration options for Linux and Unix developers or sysadmin. In this quick tip, I will explain how and why you sometimes need to ignore or exclude the ssh client config file under Linux, Unix, *BSD and macOS.
  
• How to convert JSON to CSV using Linux / Unix shell
  Today I will talk about a common problem faced by many Linux or Unix sysadmins and developers. Typically modern apps and security devices heavily depend upon APIs and lists that feed data in JSON format. For example, a list of spamming or VPN CIDRs or a good list of verified bots’ IP CIDRs is in JSON format. If they accept JSON format, you can take this list and upload it to your router or WAF. Unfortunately, not all devices accept JSON format. Hence, we can take JSON format and convert it to CSV format per our needs.
  
• How to backup & restore a list of installed FreeBSD packages
  Today, I will share one helpful tip that allows FreeBSD developers and sysadmin to make a backup list of installed all FreeBSD packages and then restore it. Hence, this is useful for disaster recovery (DR) or simply rebuilding a new server. It will save you time.
  
• How to Set Up WireGuard VPN on Amazon Linux 2
  WireGuard is an open-source, free, modern, and fast VPN with state-of-the-art cryptography. It is like OpenSSH in simplicity and uses private and public keys. Hence, it is more straightforward as compared to IPSec and OpenVPN. Initially released for the Linux kernel, it works with other operating systems. This page explains how to install and set up WireGuard VPN on Amazon Linux EC2 or Lightsail server.
  
• How to change hostname on Amazon Linux 2 without reboot
  Do you want to set or update the AWS EC2 or Lightsail hostname without a reboot when using Amazon Linux 2? Here is how to set or change the hostname on Amazon Linux 2 distribution using the ssh client.
  
• Find APT packages occupy the most space on Debian/Ubuntu
  Are you running out of disk space on your Debian or Ubuntu Linux? Do you want to know which installed Debian or Ubuntu packages occupy the most disk space? There are many ways to find out this info. In this quick tip, you will learn about listing apt or apt-get installed packages that occupy the most space using the command-line options.
  
• How to convert video to GIF in Linux using ffmpeg CLI
  In this quick Linux tip, I will explain how to convert a VIDEO file such as .mp4 into a gif file using the ffmpeg -i input.mp4 output.gif command syntax under Linux and Unix-like operating systems such as macOS.
  
• How to add Mastodon verification for the Discourse forum
  Here is a quick tip that explains how to add a Mastodon verification link for the Discourse forum.
  
• How to install git command on Alpine Linux
  Git is a distributed version control system. To install git, type apk add git command on Alpine Linux.
  
• How to hide Nginx version on Linux and 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.
  
• macOS configuring SSH Key-based Authentication
  In this quick tutorial, you will configure a user to use key-based authentication for SSH under a macOS desktop.
  
• How to run ls command case insensitive mode on Linux/Unix
  In this quick tip, I explain how to match case insensitive patterns with the ls command on your Linux, macOS, *BSD and Unix-like system.
  
• How to add swap to AWS EC2/Lightsail Amazon Linux instance
  So like many solo developers, I am tight on resources, especially money-wise. I have two AWS EC2 VMs running as WireGuard VPN on Amazon Linux for personal usage, and another one is my dev machine with Python, PHP and stuff. These are tiny VMs with just 512MB ram. The main problem is my little VM powered by CentOS or Amazon Linux 2 runs out of memory when I run “sudo yum update“. The BaseOS repo from RHEL and co is just too big. It requires a minimum of 3 GB ram. So I will also get a segfault when running out of memory as described here. I believe there is a dnf bug open in RHN. So I decided to take matters into my hands and add 8GB of swap space on Amazon Linux 2 EC2 / Lightsail VM running at AWS to fix issues.
  
• Ubuntu 22.04 Set Up UFW Firewall in 5 Minutes
  Ubuntu 22.04 LTS comes with UFW (uncomplicated firewall) that protects the desktop or server against unauthorized access. UFW is easy to use frontend app for a Linux packet filtering system called Netfilter. Traditionally Netfilter rules are set up or configured using the iptables command by developers and sysadmins. However, new Ubuntu Linux users and developers unfamiliar with firewall concepts find Netfilter syntax confusing. Hence, the ufw project provides easy to use frontend for Ubuntu 22.04 LTS Linux server and desktop. It is so super easy to set up. You can configure UFW in under 5 minutes and secure your host.
  
• How to upgrade OpenSUSE 15.3 to 15.4 using the CLI
  Right now, the most advanced OpenSUSE version is 15.4. It is an opportunity for desktop and server users running the previous 15.3 release to update to the latest software stack. The procedure for upgrading OpenSUSE 15.3 to 15.4 is simple to follow. This tutorial will walk you through the process of upgrading OpenSUSE 15.3 to 15.4.
  
• How to see Raspberry Pi OS version on Raspberry PI
  Do you want to know which version of Raspberry Pi OS is running on your hardware? Here is how to find the Raspberry Pi OS version including hardware details such as CPU, RAM and model using the command-line option.
  
• How to install dig, delv, host commands on FreeBSD
  FreeBSD default comes with a drill command to see information about DNS. The userspace tools for FreeBSD come from the latest version of the BIND-TOOLs package. It includes delv, dig, host, nslookup, and nsupdate. Let us see how to search and install dig, delv, and host commands on FreeBSD using the pkg command.
  
• How to tell ssh client to ignore ssh config file
  I have a tutorial that explains the basics of the SSH client configuration file and some of the most common configuration options for Linux and Unix developers or sysadmin. In this quick tip, I will explain how and why you sometimes need to ignore or exclude the ssh client config file under Linux, Unix, *BSD and macOS. 

Until next time.
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