Month: June 2010

Remotely upgrading a server from 32 to 64 bit linux

This post isn’t designed to be a “how to” merely an overview of how I achieved the subject. It is possible to do this without any physical intervention but in practice I have had to visit site at least once to fix a boot error on every one I have done.

Disclaimer:- When attempting this having some sort of remote access solution that will give access to the server even when it won’t boot is desirable i.e. BMC, DRAC or KVM over IP. Obviously resizing and deleting partitions and file systems is very dangerous so you need to be ultra careful and ultra sure you understand the process and exactly what you are doing at each step. It may also be helpful to draw the partition layout at each stage so you have a clear view of what is happening. Don’t come crying to me when it all blows up in your face. You have been warned!

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The merits of LXC containers

First of all what are containers? In this context we are referring to Linux running inside a “containerised” environment i.e. an environment which is to all intents and purposes isolated from the main operating system. The containerised environment doesn’t have it’s own kernel or virtualised hardware and runs at native speeds because of this.

In what ways could a containerised environment be useful and desirable from a business perspective? The first use that springs to mind is being able to easily move your dedicated server from one hoster to another (which is the way I use it). You can simply “rsync” the contents of the container from the source hoster, then take the container down, run another quick rsync and start the container at the new hoster. This is really useful, saving hours and possibly days rebuilding the server at the new hoster in a more conventional manner.

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Setup DNS, DHCP and Content Filtering using DNSMASQ and HAVP in Ubuntu.

The idea here is to setup DNSMASQ and HAVP to provide DNS, DHCP and content filtering in a Windows 7/Vista/XP client environment on Ubuntu Server Edition. DNSMASQ is a light package which will provide DNS caching and DHCP to a network (amongst other things). HAVP is a proxy server which uses a third party virus scanner (usually ClamAV) to scan internet content for viruses. This assumes that you already have Ubuntu Server Edition installed on a suitable machine and have a working internet connection. In the settings “192.168.1.254” refers to this machine which is acting as a router/firewall, you could equally set it to the ip of another router on the network. “192.168.1.253” refers to the ip of a Windows server. First off install DNSMASQ:-

apt-get install dnsmasq

Edit “/etc/dnsmasq.conf”:-

nano -w /etc/dnsmasq.conf

We now need to set the relevant options:-

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A cost effective alternative to KVM over IP switches

Whether in a co-location centre or at a remote site, looking after a server when you aren’t there in person can be a challenge, particularly if you are conscientious and update your servers regularly – updating a Windows server almost always requires reboot, updating a Linux server will require reboot if the kernel has been updated. What happens if the server doesn’t come up after said reboot? This happens more often than might be expected, so I find it desirable to have a way of accessing the server even if the operating system isn’t available. Traditionally this would be provided by a KVM over IP switch, which redirects Keyboard, Video and Mouse input/output via a web server integrated into a box. KVM over IP switches are expensive (the cheapest one I could find at time of print was €250 and doesn’t work well with mice IMO). However, there is an alternative which is elegant and affordable …

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