HowTo: Fix Postgrey not working after upgrading from an older version of Ubuntu to a newer version.

Tutorials
Scenario: You've got some Postfix mail servers running with Postgrey for anti-spam greylisting. They're all using older versions of Ubuntu such as 10.04 LTS. You've decided that it's time to upgrade them to the next LTS, Ubuntu 12.04. You do the upgrade and it goes without a hitch. You restart the server, everything looks good, until you start seeing this message in your server's mail log:   Jan 23 21:17:58 mymailserver postfix/smtpd[7976]: connect from somecompany.com[100.200.300.400] Jan 23 21:17:59 mymailserver postfix/smtpd[7976]: warning: connect to 127.0.0.1:10023: Connection refused Jan 23 21:17:59 mymailserver postfix/smtpd[7976]: warning: problem talking to server 127.0.0.1:10023: Connection refused Jan 23 21:18:00 mymailserver postfix/smtpd[7976]: warning: connect to 127.0.0.1:10023: Connection refused Jan 23 21:18:00 mymailserver postfix/smtpd[7976]: warning: problem talking to server 127.0.0.1:10023: Connection refused Jan 23 21:18:00 mymailserver postfix/smtpd[7976]: NOQUEUE: reject:…
Read More

HowTo: Create a Diskless workstation that boots from PXE using Ubuntu

Tutorials
Diskless booting is where a PC starts up purely from a network connection. It does not have a physical hard-drive in it to start from in the traditional manner. Why would you want to do this? Well, say for example you have a MythTV Frontend PC. For the most part, most Frontends are dedicated PC's connected to a TV or projector that are not used for any other purpose, so technically there is really no need to have a hard-drive inside one as nothing new will ever be stored (all the media is streamed from the Backend server). There's also the added bonus of less noise by not having a hard-drive installed. Another good example of using a Diskless boot environment is for performing offline virus scans of Windows based…
Read More

HowTo: Automatically determine your public IP address and email it periodically

Tutorials
Let's say you are running a poor man's website where you are just testing stuff but have no real intention of buying a domain name or paying your ISP to give you a static IP address. If you want to access your test site remotely, you need to know your public IP address, however your home ISP gives you a dynamic public IP address and every time you have a power failure, or reboot your router, you are assigned a brand new public IP address. This makes it very annoying if you are testing your site remotely. Sure, you could use a Dynamic DNS service to keep track of when your public IP address changes, but what if you have a paranoid client who does not want to use even…
Read More

HowTo: Configure an APC UPS to communicate with your Ubuntu Desktop or Server

Tutorials
It's been a while since I've written something here, so time to break the drought. APC make some great UPS products and they all have the ability to communicate with a host PC to advise of its state, eg: on mains, on battery, fault, etc. The support software is available aplenty for Windows and Mac, but what about Linux? This guide will show you how to hook up an APC UPS to an Ubuntu-based Desktop or Server PC and allow your UPS to email you when mains power has failed, when mains power has been restored, and also give your PC ample opportunity to shutdown when battery on the UPS gets to a critical low. (more…)
Read More

HowTo: Use lxbdplayer – the Open Source Blu-Ray Disc player for Linux

Tutorials
Yes, you read that right - there is finally an Open Source Blu-Ray Disc player GUI for Linux, albeit unofficial and certainly very grey in legality depending on which country you are in. lxbdplayer is the collaborative effort of four French Engineering students. What they have written is basically a frontend that combines the apps DumpHD and AACSKeys which I have used in previous Blu-Ray articles into one easy to use GUI. Decrypted BD streams are then piped into MPlayer for playback. The end result is that you can now watch your BD movies almost as simply as a regular video player without the need to go through the process of ripping them into an MKV file first, or chewing up loads of drive space. (more…)
Read More

HowTo: Get an Ubuntu Live CD to boot off a PXE server

Tutorials
Following my article about creating your own PXE network boot server, here is the first practical use you can put it to - taking the Ubuntu Live CD and turning it into a network-bootable version! Network booting the Live CD has obvious advantages - aside from booting faster than CD (especially on a gigabit network), it is indispensable as an emergency boot medium in a workplace environment, especially for broken Windows systems, and allows for Ubuntu effortless installations on netbook PC's that don't have optical drives and saves you having to have a USB stick handy. (more…)
Read More

HowTo: Setup your own PXE Boot Server using Ubuntu Server

Tutorials
The Preboot eXecution Environment (PXE) provides a means of starting up a PC using a network adapter instead of the traditional method of hard-drive, USB flash stick, CD or floppy disk. Why would you want to boot a PC from the network? Well, it opens the door to booting diskless workstations, eg: Internet Cafe PC's, or if you regularly install tens or hundreds of PC's, you can start the installer on all those machines at once without needing to have individual boot/install media for each machine. You can even use Linux PXE for starting Microsoft Windows network installers and tools. This article is going to show you how to setup a standard Ubuntu 10.04 Lucid Lynx Server (will also work with Ubuntu 12.04 and 14.04) to respond to a PXE…
Read More

HowTo: Swap the window gadgets back to the right side of the window in Ubuntu Lucid.

Tutorials
The release of Ubuntu's brand new look in Ubuntu 10.04 Lucid Lynx Alpha 3 brought mixed reactions, but probably none more so than the decision to move the window minimise, maximise and close gadgets from their traditional placement on the upper-right corner of the window to the upper-left side ala Apple Mac. Many people, myself included, do not like this. To fix it and make it look like this: ...is very easy to do. Read on. (more…)
Read More