I upgraded my T420 because Ubuntu Mate 19.10 now supports the Nvidia Optimus drivers and includes a utility that lets me switch between Intel and Nvidia graphics cards. However, the upgrade seemed to break the power management on my laptop. When running on the battery, the laptop would suddenly lose power after only 10 minutes, even when the battery still shows ninety percent charge.

I installed Linux Advanced Power Management, TLP. TLP solved my problem. Also, for good measure, I upgraded the BIOS because, while troubleshooting this issue, I discovered is was very out of date.

In his post, I describe how to install and configure TLP and how to upgrade the BIOS on a Lenovo Thinkpad T420.

Continue Reading…

Antidote is the network emulator that runs the labs on the Network Reliability Labs web site. You may install a standalone version of Antidote on your personal computer using the Vagrant virtual environment provisioning tool.

In this post, I show you how to run Antidote on a Linux system with KVM, instead of VirtualBox, on your local PC to achieve better performance — especially on older hardware.

Continue Reading…

I installed the Azure CLI in the Termux app on my Android phone. This post describes all the steps required to successfully run Azure CLI on most Android phones.

Installing Azure CLI on Termux on your Android phone is an alternative to using Azure Cloud Shell on Chrome or Firefox, or to using the Cloud Shell feature on the Azure mobile app. It’s also a cool thing to try.

Continue Reading…

I want to show you how to configure a host server so, when it is shut down, it executes a script that runs commands on any running virtual machines before the host tries to stop them. I will configure the host server to wait until the script completes configuring the virtual machines before continuing with the shutdown process, shutting down the virtual machines, and eventually powering off.

I had to learn how Systemd service unit configuration files work and some more details about how Libvirt is configured in different Linux distributions. Read on to see the solution, plus some details about how to test the solution in Ubuntu and CentOS.

Continue Reading…

Yesterday, I participated in a screen-cast with Derick Winkworth, aka @CloudToad, to discuss my blog posts about installing NRE Labs Antidote network emulator on your PC and creating lessons for NRE Labs. We also covered some general points like contributing to communities, how to get started blogging about technical topics, and more. Check it out, below:

This video, and other NRE Labs videos are available on YouTube. Also, the NRE Labs team runs a live screen-cast every Monday at 1:00 PM using the Discord app. Join the NRE Labs Discord channel and engage in the discussion.

The Antidote network emulator, part of the Network Reliability Engineering project, offers a web interface that presents network emulation scenarios to users as documented lessons. Each lesson is presented in a window running Jupyter Notebooks and contains commands that the user can click on to run them on the virtual nodes in the network emulation scenario.

nrelabs lessons

The NRE Labs developers intend for Antidote to be used as an educational tool. Its lesson-focused user interface supports students’ learning progress. This post is a tutorial showing how to create and test two simple, but different, Antidote lessons.

Continue Reading…

Antidote is a network emulator combined with a presentation framework. It was designed to create and deliver networking technology training. Its user interface operates in a web browser, including the terminals that students use to run commands on emulated network devices and servers.

Antidote is the engine that runs the Network Reliability Labs web site. Antidote is an open-source project, released under the Apache license. A standalone version of Antidote may be installed and run on your personal computer using the selfmedicate script. In this post, I will install Antidote and configure it to improve Antidote performance on my Linux system.

Continue Reading…

Wistar is an open-source network emulator originally developed by Juniper Networks and released under the Apache license. It simplifies the presentation of Juniper products on its graphical user interface by making the multiple VMs that make up each JunOS virtual router appear as one node in the network topology.

Wistar also supports Linux virtual machines and, interestingly, uses cloud-init to configure Linux routers from the Wistar user interface. Wistar also supports generic virtual appliances, in a basic way. In this post, I will install Wistar and use it to work through two examples using open source routers.

Continue Reading…

Vrnetlab, or VR Network Lab, is an open-source network emulator that runs virtual routers using KVM and Docker. Software developers and network engineers use vrnetlab, along with continuous-integration processes, for testing network provisioning changes in a virtual network. Researchers and engineers may also use the vrnetlab command line interface to create and modify network emulation labs in an interactive way. In this post, I review vrnetlab’s main features and show how to use it to create a simple network emulation scenario using open-source routers.

Continue Reading…

In this post, I demonstrate how to create a network emulation scenario using Libvirt, the Qemu/KVM hypervisor, and Linux bridges to create and manage interconnected virtual machines on a host system. As I do so, I will share what I have learned about network virtualization on a Linux system.

Libvirt provides a command-line interface that hides the low-level virtualization and networking details, enabling one to easily create and manage virtual networking scenarios. It is already used as a basis for some existing network emulators, and other applications and tools. It is available in almost every Linux distribution.

Continue Reading…

Are you like me? Are you a network engineer, or other professional, transitioning their skill set to include programming and automation? Does your programming experience experience come from a few programming courses you attended in college a long time ago? Then please read on because I created this Python guide for people like you and me.

In this guide, I explain the absolute minimum amount you need to learn about Python required to create useful programs. Follow this guide to get a very short, but functional, overview of Python programming in less than one hour.

When you begin using Python, there are a lot of topics you do not need to know so I omit them from this guide. However, I don’t want you to have to unlearn misconceptions later, when you become more experienced, so I include some Python concepts that other beginner guides might skip, such as the Python object model. This guide is “simple” but it is also “correct”.

Continue Reading…

Microsoft Azure unofficially supports nested virtualization using KVM on Linux virtual machines, which makes it possible to build network emulation scenarios in the cloud using the same technologies you would use if you were using your own PC or a local server.

In this post, I will show you how to set up a Linux virtual machine in Microsoft Azure and then create a nested virtual machine inside the Azure virtual machine. This is a simple example, but you may use the same procedure as a starting point to create more complex network emulation scenarios using nested virtualization.

Continue Reading…