My life managing systems, especially distributed, has gone much easier since I started using more and more of CoreOS awesomeness. CoreOS is a new Linux distribution that has been rearchitected to provide features needed to run modern infrastructure stacks. The main features of CoreOS which I like are that it is very minimal, read-only and most importantly comes with etcd out of the box. As it…
HAProxy is amazing piece of software. It is rock solid, extremely flexible and has been proven by many companies which depend on it. I use haproxy as a load balancer and service discovery. It runs on each CoreOS node and proxies traffic through to healthy services running on CoreOS cluster inside docker containers. This post is not about how that works, but rather how to get haproxy log to syslog…
There are a lot of companies which are still discovering puppet, chef or saltstack. Sadly, there are ones which are yet to discover configuration management. While companies like Google have been running everything inside containers for over a decade. I always try to keep up with ever changing technologies and best practices. I have been using docker for quite some time and recently have started…
The word DevOps has been out there for a while. Some believe it is just a buzz word, others - it’s a work culture and recruiters insist that it’s a job position, but let’s leave that to them. We shall try to eliminate silos between Operation and Developer teams and not to create another silo called ‘DevOps Engineer’. There is a lot of fuzz about this already, so let’s move on to some real…
I was slightly familiar with elasticsearch and logstash before at a very minimum level. But just a couple of days ago I had a chance to play with both toys at a larger scale. I was given a box with elasticsearch, redis and logstash already running, it was actually barely alive, so overwhelmed, elasticsearch was constantly timing out and redis in-memory database was running out of allocated memory.…
I will try to be open minded here as much as I can. I am a huge fan of rpm-based Linux distributions, such as Fedora and CentOS/RHEL. They are super clean, stable, predictable . Usability is great too. I don’t care about care that Fedora comes with Gnome3 by default and some say that Gnome3 sucks is unstable and usability is terrible, but I like it. All I need from desktop environment is to be…
This is a follow up post to my previous post on pretty much the same topic. The main reason I am writing again is that there are still a lot of people confused how to get FN keys working properly and there is a reason for people to be confused, because I did not mention about how buggy Samsung’s firmware is - once you press a function key, it does not send a key release event back to the kernel,…
Few words for a warm-up Few months ago I bought myself a brand new and shiny ultrabook from Samsung. It obviously came pre-installed with Windows7. I quickly rushed to wipe the evil OS out, before I did an SSD clone, just in case I will ever need Windows7 on this laptop again. Right, so it was time to install my favourite linux distribution - fedora! There was only fedora15 available back then, so…
I will show you a very nice and non-intrusive way how to log bash history to a syslog. You may wonder what problem I was trying to solve? Right, the issue is that I want to log root users bash history from multiple servers to a central syslog box. I also want to preserve root users history on each server for convenience purposes. But first let’s talk about my failed attempts to do so. Failed…
You may wonder why I am writing about yet another free DNS hosting service, after all there are quite a few of them out there already. If you think so, then you’re probably right, there are at least 4 DNS services where you can host your own domain/zone for free, but there is always a catch. They either start charging you if you want to add more domains/zones or if your domain is a popular one and…
Intro How many of our managed servers have PXE boot capable NICs? Who really wants to move his ass and crawl to a data centre to manually build a server? Trust me - there are people who really enjoy doing that. But I do not, and whoever is reading this post does not either I guess. Doing stuff I will share with you a nice little trick which can be useful if you cannot boot off your servers of a…
Here is a quick step by step tutorial howto rebuild a CentOS 6 kernel (it may work with older CentOS). WARNING: never build RPMS as root!!! I will be using a kernel version 2.6.32-71.29.1.el6 as an example. * Grab an SRPM from (http://mirror.centos.org/centos/6/updates/SRPMS/kernel-2.6.32-71.29.1.el6.src.rpm) * Install the rpm (as a regular user, this will install the source RPM into…
I spent a bit of time figuring out how to get this achieved, so thought it is worth noting for the future reference. I will try to make this quick assuming you have knowledge about iSCSI software initiators in Linux. Tested on CentOS 6.0 it may work on CentOS 5.0 and alternatives. Software used: udev-147-2.29.el6.x86_64 iscsi-initiator-utils-6.2.0.872-10.el6.x86_64 Steps to make this work: First…
If you are also very desperate for CentOS 6.0 as I am, you might find the below one-line script useful to check if any of the official CentOS mirrors has got 6.0 already synced. This tiny script automates the process of going through the mirror sites and checking if 6.0 folder exists :-) You will need curl, ncftp and obviously bash for the script to work. You can add it to cron, so it gets run…
Introduction Asterisk is software that turns an ordinary computer into a communications server. Asterisk powers IP PBX systems, VoIP gateways, conference servers and more. This howto covers topics and issues installing, configuring and managing Asterisk server on Fedora Linux version 12 to 14. It is based on Asterisk 1.6.2. Installation I assume you are going to be using Asterisk and its…
First of all, let me introduce roughly what Ganglia is. Ganglia is a scalable distributed monitoring system for high-performance computing systems such as clusters and Grids (taken from http://ganglia.sourceforge.net homepage). So basically it is for people who want to have an idea what their bunch of super-computers are doing as a whole (it monitors nodes as individuals too). I have been using…
Thought I will write a tiny post about how to easily monitor NEW (or any other state) connections per second on a Linux firewall. The approach I have chosen seems to be really easy and simple one-liner. Kernel modules and packages you are going to need: ip_conntrack iptables kernel module loaded or compiled in to the kernel conntrack-tools package installed libnetfilter_conntrack package installed…
Intro Recently I had some joy to build a diskless linux cluster for parallel regexing. So I decided to document it how I accomplished that using free and open source software. There is very little or very old documentation on how to build a diskless cluster using linux distributions. This howto explains the setup of using a single compressed root file system image as a ramdisk for the slave nodes.…
As everyone else, the very first step in programming and probably in blogging world is a Hello World thing, so I am going to do the same. I am still getting used to the WordPress user-friendly interface and various tools available. So far so good and I like it :-) Here is my Hello World in bash: #!/bin/bash printf "%s\n" 'Hello World!' More posts to follow, hopefully some people will find it…