Saturday, 24 December 2011

Raspberry Pi - A £16 Linux PC!



A credit card sized computer being developed by a UK based charitable foundation that is hoped will promote the education of computer science at school level and beyond.

The idea is simple - develop, manufacture and distribute an ultra-low-cost computer, for use in teaching computer programming to children.

That said, the computer can be used for many of the things that a desktop PC is, like spreadsheets, word-processing, games and high-definition video playback.


The name of this computer is the Raspberry PI:


OK, so what is the idea here?  What are they trying to achieve?  Games developer David Braben explains to BBC's Rory Cellan-Jones, holding an early alpha model, back in May 2011:
 

Here is a basic layout, detailing the features on board:


As can be seen from the above, the RasPi will be shipped in two variants:

  • Model A = 128MB RAM on board, no Ethernet = $25 / £16
  • Model B = 256MB RAM on board, 10/100 UTP Ethernet port = $35 / £22

So what do you get for your money?  Well, quite a lot actually:

  • 700MHz ARM11 Processor - The same processor as found in many mobile phones (including my ZTE Blade!)
  • 1080p full HD video output - via HDMI connector
  • Composite connector - for direct connection to a TV
  • Dual USB2 ports - for keyboard, mouse, etc
  • SD/MMC/SDIO memory card slot - for operating system etc etc

Talking of operating systems, it is envisaged that Debian Linux, Fedora Linux and ArchLinux will be supported from the start.  Other Linux distributions maybe supported later.

So what does it run like?  Have a watch for yourself:



Not to shabby at all!

As a father of an 11 year old son who is nuts on anything computer related (wonder where he gets that from? hehehe) I can certainly expect to see at least one of these winging their way to Kent!

What's even better is that there are already RasPi based coding tutorials on youtube, such as Liam Frasier's Raspberry Pi Tutorials channel.

So when is it going to be available?  By the looks of it very soon.  At the time of writing this (24 Dec 2011), the beta boards are currently undergoing testing and with all going well, the first first production run will be early in 2012.

Keep an eye on the Raspberry Pi Blog and on the official Raspberry PI Twitter feed for updates.

Excellent stuff!

- Chris

Monday, 19 December 2011

vSphere VM Clone Problems + Fixes


Just recently a colleague of mine had some fun and games completing what should have been a simple clone of Windows 2008 R2 64bit VMware virtual machine.

We managed to get to the bottom of the issues and get the clones completed, so for future info and help of others here are the issues and resolutions to those issues encountered.






autochk program not found - skipping AUTOCHECK and STOP: c000021a BSOD

Clone VM created successfully, however upon first boot of the VM, the following were seen:



According to VMware KB Article 2004505 this is caused by the entry:

disk.EnableUUID = "TRUE"
in the source VM's virtual machine configuration (vmx) file.  Download, edit and upload the vmx with the following setting:

disk.EnableUUID = "FALSE"
See the VMware KB article for further details around editing virtual machine vmx files.



Windows could not finish configuring the system...

Again, clone VM created successfully, however upon first boot of the VM, the following was seen:


According to the Microsoft KB Article KB981542 this issue occurs if the original operating system contains a registry key that is larger than 8 kilobytes (KB).

The resolution being to install a patch on the source VM. 

Unfortunately the patch is not available on the MS website, however it is available here:

After overcoming both those issues, the VM clones completed and booted successfully and what should have been a quick and easy job was done.

Thanks should go to Alan for highlighting the issues and persevering with the fixes.... both of them!

- Chris

Thursday, 15 December 2011

Find HBA WWNs from ESXi Console


 A question this comes up quite a bit:  How can I find the World Wide Names (WWNs) of the fibre channel Host Bus Adapters (HBAs) my ESXi server from the console?

Sure you can use the VMware VI client to gather the required info, but what happens if you do not or have network connectivity to your ESXi yet? 

The WWN information is very often needed to for the zoning configuration on the fibre channel switches to ensure that the ESXi server can only access the Storage Array Network (SAN) disks it is supposed to access.




Here is how to find the HBA WWNs:

First log on to your ESXi console:
Now select Troubleshooting Options:

Then select Enable Local Tech Support:

Now press ALT F1 to enter local ESXi console:

Login using root credentials:

At the # prompt enter: cd /proc/scsi and ls to list the SCSI adaptors fitted in your ESXi:


You are looking for qlaxxxx for QLogic HBAs or lpfc for Emulex HBAs.  As you can see from the screenshots, my ESXi has QLogic adapters fitted (qla2xxx).

Next, cd qla2xxx (or cd lpfc for emulex) and then list (ls) adaptors:


As you can see I have adaptors fitted at 5 and 6.  Your numbers may (and quite likely will) be different.  The last step is to list each of the adaptors found, using the cat x |more ("x" being one of the numbers listed) command:
 You are looking for the Host Device Name and the SCSI Device Information:
 

OK.  To get the full WWN address, simply note down the node and port hex ID's from the SCSI Device Information, and separate each pair with colons ":" to make your full HBA WWN.  In my case, from the screenshots above, my HBA WWN would be:

WWN of vmhba2 = 20:00:00:1b:32:8a:f3:42 21:00:00:1b:32:8a:f3:42

Repeat for the last command (cat x |more) for all the other HBA's in your ESXi (so in my case I would run the command cat 6 |more to find the SCSI device information for my other HBA.

When finished type exit to return to the ESXi tech support console login and ALT F2 to switch back to the standard ESXi console.

Don't forget to login, select Troubleshooting Options and Disable Local Tech Support when completely finished!

- Chris

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