List of Linux Articles

A collection of Linux meanderings, mostly written from a System Administrators perspective...


PostgreSQL Replication: Failover

2016-03-14T20:30:00Z

I've spent the last few days equipping myself with the knowledge I need to support failover of our data tier from production to disaster recovery and vice-versa. In the lab I built a series of PostgreSQL Servers and set up replication between them. In this article I explore failover. Failover Scenario I'm…

PostgreSQL: Basic Replication with Synchronous and Asynchronous Hot Stand-by

2016-02-11T20:30:00Z

I've spent the last few days equipping myself with the knowledge I need to support failover of our data tier from production to disaster recovery and vice-versa. In the lab I built a a series of PostgreSQL Servers and set them up replication between them. This article describes how. The Desired…

Creating an LXC Containerized Selenium Grid

2015-12-08T20:30:00Z

This guide shows you how to build one or more self-contained Selenium grids using: Ubuntu Server 14.04.3 LTS Selenium Server 2.48.2 LXC containers for each grid node - this means we can run more tests in parallel without running into Selenium/Firefox mutex problems vnc4server and Openbox to provide a desktop - sometimes developers like…

Building a ZFS Backup Server

2015-11-16T20:30:00Z

I've been running an Ubuntu home server with ZFS based storage for sometime. What follows is a rather detailed walk through my implementation of a ZFS backup server. I have been meaning to implement ZFS snapshot based backups for quite some time and I figured I may as well document…

Resolving a GlusterFS Server Failure

2015-09-30T19:30:00Z

I'm responsible for maintaining four servers that have been built for running automated browser tests using Selenium. Each server runs a selenium hub and multiple XVNC desktops / selenium nodes. The tests are run in Firefox and the Firefox profile utilised by Selenium imports the Firebug Firefox extension. The profile…

Resolving DNS Resolution Issues in Ubuntu and Ubuntu Derived Distros

2015-09-24T20:00:00Z

Using Ubuntu 12.04/12.10 and later versions/derivatives (including my current desktop distro of choice, Linux Mint), I have had periodic issues with programs resolving the IP addresses of hosts on the local network. These are easily resolved with just a handful of configuration tweaks. dnsmasq The first problem I noticed, was an occasional…

What's eating all my disk? Using 'du' in Linux

2015-09-23T17:30:00Z

I've just been awakened courtesy of an alert from Nagios kindly advising that a host is down. That was very quickly resolved, but whilst I was awake I noticed a warning for disk space utilisation on one of the Selenium test runners used in our development environment, so I decided…

Blocking an IP Address with iptables

2015-09-16T09:00:00Z

I have this blog hosted on a VPS which is protected by Fail2Ban. Thus far I've found most would-be attackers quickly move on when their IP addresses have been blocked a few times. Occasionally one of the blighters will persist, hence I use iptables to permanently drop all of the…