Monthly Archives

October 2009

Channelling messages from beyond…

OK, so who owns a BT Home Hub?  I’m sure many tens of you do, as that’s the default solution from BT for home internet connections. And I’m sure its a great product.  However, they seem to cause me nothing but trouble – you see, I don’t use BT as an ISP as they’re comparatively expensive, low on functionality, and reports indicate that its quite slow and unreliable too.   So, I’ve got my own Wifi routers (Linksys WRT54gl’s) in the house which run a custom firmware and allow me to set them up just so.  Three of them ensure that I have total wifi coverage at Very Good or above throughout the house.  Or that’s the theory.

For those that don’t know, here’s a brief technical overview of how wifi works…   Wifi is generally split into 4 types – A, B, G and N, with A & N running at 5 Ghz, and B, G (and N) running at 2.1 Ghz.  5 Ghz offers around 19 channels in Europe with 20 Mhz separation, which is fine.  However,  2.1 Ghz only offers 13 channels spaced 5 Mhz apart, but the wifi protocol requires 25mhz of separation.  This means that in reality, there are only three or four channels that can be used without clashing with other networks.  And that’s assuming that you’ve no other devices on the 2.1Ghz band such as Bluetooth, baby monitors,  TV senders,  wireless video game controllers – even microwaves and fluorescent lights can generate radio noise on this band.

A few minutes spent planning the network can reduce the impact that this has, even for a single access point.  The diagram shows the spectrum coverage of the given wifi channels, and you can use this to work out what the optimal settings for your network is.

File:2.4 GHz Wi-Fi channels (802.11b,g WLAN).png

So what you need to do is find out what channels your neighbours network is on (many wifi drivers and access points will show you).  If for example they’re on channel 11,  you could use 7 downwards.  Where it becomes more complicated is when you have neighbours both sides with wifi – you’ve got to slot in with them and hope that there are free channels available.

But back to my original point – flippin BT HomeHubs!  Most of my neighbours seem to be using them, which is fine, BUT the HomeHubs don’t seem to be able to pick a channel and stick with it – except when manually configured to do so! Every few weeks I find my wireless has gone to hell, and I look, and one of the hubs has changed its channel to the opposite end of the spectrum which means recalibrating my setup to get the best I can with the least overlap.  What’s most annoying is that they seem pretty useless at seeing what’s available and will often arbitrarily pick channel 6 or 7 no matter what is around them!  Which makes it pretty difficult to configure the network without any overlap.  My only hope is 802.11n (N networks) will go someway to improve this, but I don’t currently have any experience on its impact, other than it is supposed to be better in noisy environments.  But for now, I’ll stick with wired ethernet where I require guaranteed service such as to my media server, as its the only way of ensuring a consistent an reliable connection. 

And if you find your wireless experience is awful, check your channel assignment – the chances are you and your neighbours are all shouting at the same time and drowning each other out!

Installing Debian Lenny on ML370 G3 with RAID Controller.

Whilst Debian Lenny is compatible with the Compaq/HP ML370 G3 with RAID Controller on-board, it took me a little work to get it installed and I wanted to document my efforts for myself and others!  This was a painful process to get it working, and perhaps isn’t for the weak of heart or those early in their Linux-ninja training, but hopefully this will guide you to the path of enlightenment and joy!

An ML370 G3 with sufficient hardware to boot/install e.t.c.
A copy of HP SmartStart (I used 7.20, others may work).
A copy of Windows 2003 (2000 may also work).
Debian Lenny NetInst CD
USB Stick formatted as FAT with ‘non-free’ Array Controller Driver saved to it (ql2300_fw.bin in my case).

How I did it:-

  1. Connect up the machine, power on and insert the HP SmartStart CD
  2. Once the SmartStart has booted, configure your array(s) as per your requirement.  In my case, I used 2x147GB drives in a RAID1 and 4x72GB drives in a RAID5.
  3. Do an operating system install, choose to install Windows and let it do its own partitioning.
  4. Let Windows install, don’t bother doing any major configuratoring as you’re going to wipe the server again shortly…
  5. Once Windows is installed and on the desktop, insert the Debian CD and Reboot.
  6. Boot to the Lenny Installer, and choose a ‘Standard Install’.
  7. Configure as normal.
  8. When you get to the bit about partitioning, choose the Manual Option.
  9. Goto the NTFS partition that the Windows install created, change it to an Ext3 format, ensure it is set to be bootable, and set the mount point to be /.
  10. Id leave other partition configuration until the point that you can boot Linux.
  11. Carry on and install whatever packages/components you require as standard.
  12. When you’re prompted to install the GRUB bootloader into the MBR – SAY NO
  13. You’ll be asked where you want to install the bootloader.  My partition was /dev/cciss/c0d0p1.
  14. Finish off the Installer, remove the CD and Reboot.
  15. Fingers x’d, you’ll get GRUB boot menu.  Mine then refused to boot the OS saying that the Operating System wasn’t found.   I edited the initial boot menu because it was referring to HD (1,0).  I changed this to HD (0,0) and it booted.
  16. Login to the console.
  17. If the GRUB editing worked, make sure to edit /boot/grub/menu.lst and permanently change the setting to HD (0,0) for each of the menu items.

Cool Runnings:-
This server when running at full tilt with the fans is a noisy noisy beasty! However, you can control those fans to make them run at a dull roar rather than full hurricane force chat.  Follow the instructions from Jonas Bjork related to Ubuntu. Debian works exactly the same way, but you’ll need to install SNMPD and libstdc++2.10-glibc2.2 (the latter you’ll have to manually download the .deb from the Etch repository).  Once its all installed, run the ‘hpasm activate’ command and follow the on-screen instructions.


Phish and Chips?

Do you use Windows Live/MSN/Hotmail/Windows Passport?  What about Google, AOL and Yahoo services?  If so, you may be well changing your password.  A large list of user accounts are believed to have been ‘phished’ from Internet users across the globe, originally thought to be centered on the Windows Live services, but now appears to be spread across many of the top companies.

Now, Phishing is quite a common occurrence related to IT security, but it certainly serves as a reminder that you should follow a few simple rules on the Internet and in Email.

  • Always use different, complex passwords on each service you register for.
  • Change those passwords on a regular basis
  • Never respond to requests for information, either via email or pop-up messages.  If you receive an email from a company that you do business with, go to their website directly – NEVER EVER EVER click on a link provided by email.
  • Engage brain before operating hand or mouth – Stop, take a deep breath and think about what you’re being asked for.  Don’t give it out and if you feel like you have to, why not give false information instead?
  • Check your statements/accounts regularly for any irregularities, and if you spot anything, contact the company IMMEDIATLY.
  • Many companies have a contact us area which you can report phishy emails to.  They will be able to investigate on your behalf and notify the relevant authorities.  Again,  visit their website by entering the address manually in the browser rather than clicking a link.

If you have difficulty remembering your passwords or building complex passwords to use,  why not investigate the KeePass utility.   This is a secure password vault in which you can store a database of usernames, sites and passwords in a safe, encrypted manor. I’ve started using it on my home computer and also on my mobile phone whilst at work (with synchronised databases) and allows me to keep a record of all of the websites Ive registered for and the secure password associated with it.  That way, all I have to do is remember one secure password to unlock the vault rather than 50-100 or use the same password across multiple services.  You should just remember to back it up regularly to ensure that you don’t loose all your passwords in one fell swoop!

The BBC have an article on the attack HERE.