Linux based distributions have featured set of commands which provide way to configure networking in easy and powerful way through command-line. These set of commands are available from net-tools package which has been there for a long time on almost all distributions, and includes commands like: ifconfig, route, nameif, iwconfig, iptunnel, netstat, arp.
These commands are just about sufficient in configuring the network in a way any novice or an expert Linux user would want, but due to advancement in Linux kernel over past years and unmaintainable of this packaged set of commands, they are getting deprecated and a more powerful alternative which has ability to replace all of these commands is emerging.
This alternative has also been there for quite some time now and is much more powerful than any of these commands. Rest of sections would highlight this alternative and compare it with one of the command from net-tools package i.e. ifconfig.
This tutorial will demonstrate how you can use Corosync and Pacemaker with a Floating IP to create a high availability (HA) server infrastructure on DigitalOcean.
Corosync is an open source program that provides cluster membership and messaging capabilities, often referred to as the messaging layer, to client servers. Pacemaker is an open source cluster resource manager (CRM), a system that coordinates resources and services that are managed and made highly available by a cluster. In essence, Corosync enables servers to communicate as a cluster, while Pacemaker provides the ability to control how the cluster behaves.
When completed, the HA setup will consist of two Ubuntu 14.04 servers in an active/passive configuration. This will be accomplished by pointing a Floating IP, which is how your users will access your web service, to point to the primary (active) server unless a failure is detected. In the event that Pacemaker detects that the primary server is unavailable, the secondary (passive) server will automatically run a script that will reassign the Floating IP to itself via the DigitalOcean API. Thus, subsequent network traffic to the Floating IP will be directed to your secondary server, which will act as the active server and process the incoming traffic.
This diagram demonstrates the concept of the described setup:
Note: This tutorial only covers setting up active/passive high availability at the gateway level. That is, it includes the Floating IP, and the load balancer servers—Primary and Secondary. Furthermore, for demonstration purposes, instead of configuring reverse-proxy load balancers on each server, we will simply configure them to respond with their respective hostname and public IP address.
To achieve this goal, we will follow these steps:
- Create 2 Droplets that will receive traffic
- Create Floating IP and assign it to one of the Droplets
- Install and configure Corosync
- Install and configure Pacemaker
- Configure Floating IP Reassignment Cluster Resource
- Test failover
- Configure Nginx Cluster Resource
Django is a powerful web framework that can help you get your Python application or website off the ground. Django includes a simplified development server for testing your code locally, but for anything even slightly production related, a more secure and powerful web server is required.
In this guide, we will demonstrate how to install and configure some components on Ubuntu 16.04 to support and serve Django applications. We will be setting up a PostgreSQL database instead of using the default SQLite database. We will configure the Gunicorn application server to interface with our applications. We will then set up Nginx to reverse proxy to Gunicorn, giving us access to its security and performance features to serve our apps.
A detailed guide to setting up your machine for deep learning research. Includes instructions to install drivers, tools and various deep learning frameworks. This was tested on a 64 bit machine with Nvidia Titan X, running Ubuntu 14.04
There are several great guides with a similar goal. Some are limited in scope, while others are not up to date. This guide is based on (with some portions copied verbatim from):
Ubuntu 16.04 Xenial Xerus is finally out with full ZFS support. So I embarked on a journey to get a fileserver up and running with the goal to:
- Boot from ZFS
- Have a Raid 10
- (Raid 10 is not a requirement for this tutorial to work)
- Use the Ubuntu Desktop DVD for the installation
- ZFS UEFI installation does not work in VirtualBox
- Putting the boot partition inside a zpool does not work. Use a separate UEFI partition for
- Grub2 has to be installed after the first time you booted your newly installed system
- Follow this tutorial
At its simplest, LXD is a daemon which provides a REST API to drive LXC containers.
Its main goal is to provide a user experience that’s similar to that of virtual machines but using Linux containers rather than hardware virtualization.
How does LXD relate to Docker/Rkt?
This is by far the question we get the most, so lets address it immediately!
LXD focuses on system containers, also called infrastructure containers. That is, a LXD container runs a full Linux system, exactly as it would be when run on metal or in a VM.
Those containers will typically be long running and based on a clean distribution image. Traditional configuration management tools and deployment tools can be used with LXD containers exactly as you would use them for a VM, cloud instance or physical machine.
In contrast, Docker focuses on ephemeral, stateless, minimal containers that won’t typically get upgraded or re-configured but instead just be replaced entirely. That makes Docker and similar projects much closer to a software distribution mechanism than a machine management tool.
The two models aren’t mutually exclusive either. You can absolutely use LXD to provide full Linux systems to your users who can then install Docker inside their LXD container to run the software they want.
What is Shashlik
The goal of Shashlik is to provide a way to run Android applications on a standard Linux desktop as easily and simply as possible.
Under the hood
The easiest way to run an Android app correctly is to simply run Android. It’s a linux base that we can nest inside our session. OpenGL and graphics are all rendered on the host ensuring fast performance.
Shashlik provides an incredibly stripped down Android base which boots directly into the loaded app, but with a running activity manager and daemons so that intents still work correctly.
“Ubuntu 16.04 LTS (Xenial) is only a few short weeks away, and with it comes one of the most exciting new features Linux has seen in a very long time…”
“In this tutorial I will walk you through the steps for using Ansible to install and deploy the open source NGINX software and NGINX Plus, our commercial product. I’m showing deployment onto a CentOS server, but I have included details about deploying on Ubuntu servers in Creating an Ansible Playbook for Installing NGINX and NGINX Plus on Ubuntu below…”
“Canonical just announced a new, free, and very cool way to provide thousands of IP addresses to each of your VMs on AWS. Check out the fan networking on Ubuntu wiki page to get started, or read Dustin’s excellent fan walkthrough. Carry on here for a simple description of this happy little dose of awesome.
Containers are transforming the way people think about virtual machines (LXD) and apps (Docker). They give us much better performance and much better density for virtualisation in LXD, and with Docker, they enable new ways to move applications between dev, test and production. These two aspects of containers – the whole machine container and the process container, are perfectly complementary. You can launch Docker process containers inside LXD machine containers very easily. LXD feels like KVM only faster, Docker feels like the core unit of a PAAS.
The density numbers are pretty staggering. It’s *normal* to run hundreds of containers on a laptop.
And that is what creates one of the real frustrations of the container generation, which is a shortage of easily accessible IP addresses.
It seems weird that in this era of virtual everything that a number is hard to come by. The restrictions are real, however, because AWS restricts artificially the number of IP addresses you can bind to an interface on your VM. You have to buy a bigger VM to get more IP addresses, even if you don’t need extra compute. Also, IPv6 is nowehre to be seen on the clouds, so addresses are more scarce than they need to be in the first place.
So the key problem is that you want to find a way to get tens or hundreds of IP addresses allocated to each VM…”