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Re: [ALUG] latest solar info
by Wayne Stallwood 20 Feb '10

20 Feb '10

Jenny Hopkins wrote: >> Confused about solar. Tony reckons the inox have mirrors on the >> outside that need servicing, but Wayne showed me that the solaressence >> ones trhat he has have a newer version that have them on the inside. >> > > Reflector details vary, but it's all terribly minor details. All you > should care about is overall cost vs. power output. Is tony suggesting > that you need to get up on the roof every 10 years and wipe down the > reflectors? Probably a good idea. Mine are still v.shiny after 2 yrs. > A wipe in another few years might be an idea. > > Internal reflectors must be smaller, by definition, so collect less > sun. Refelectors of any design make no more than 10% difference to > output. At most sun angles they are hidden behind the tubes. > > Is this from wookey ? I agree with everything he is saying there..the reflectors help with severely off axis sunlight and try and bounce some back onto the tubes...this helps me a tiny bit I think in the afternoons during the autum/spring where the sun's angle is such that as of about 3PM it is hitting the tubes more from the side than above. Yes my CPC mirrors are internal to the tubes and therefore smaller and less efficient than the ones that sit under the tubes with the advantage that they can't get dirty...but I can't imagine external CPC mirrors need frequent cleaning as has been claimed..and the tubes themselves will only get mucky at the same rate as a flat panel. The flat panel systems were shown to be the basis of less efficient systems (when a whole years savings were taken into consideration) in a DTI report done in 2001...since then Evacuated Tube panels have only improved (and as far as I am aware there have been no further developments in flat panel tech) As I understand it the issue with panels is two-fold...one there is a big surface area to radiate collected heat before it can be drawn down to the tank..so on cold but sunny days you are losing some potential. Also as soon as the light output is a bit too far off axis you get significant reflection losses from the flat collection area..whereas naturally with a tube, part of the surface is on axis at all time sun is hitting that area of roof. Generally everything I have read says that in a climate that can be cold but sunny or where there is frequent cloud cover you will see better results from a ET setup..which is why most modern installations in this country seem to be using that technology. This becomes even more important if you are considering a dual setup where it is going to be assisting heating as well as hot water as of course you want whatever you can get from the panel on the colder days. The other issue with FP collectors as I mentioned on IRC is that although FP technology is now 30 years old and well proven..if you do get a problem with a panel then the only option is to replace the whole unit which is both expensive and cumbersome..requiring a system drain and re-pressurisation afterwards (and probably lifting tackle/roof platforms if the repair was going to be done with health and safety in mind as they are very heavy). My tubes are indirect and can be replaced cheaply, individually, and without touching the solar circuit. Also a single damaged tube will not compromise the operation of the rest of that panel. The one downside here is that ET panels are relatively new technology and haven't been on anyones roof for more than 10 years or so..so long term life predictions are just that..predictions. Whereas I know there are people around with 25 year old flat panels that are still working. There are two (admittedly looking quite old) FP installations near me and both have a damaged panel now..one is just clouded so I assume a weather seal has gone somewhere and the other has what looks like it might have been some nutcase with a catapult because the FP is visibly cracked. Both have remained like that for at least a year, presumably because repair would be expensive. A single tube for my system costs about the same as a meal out somewhere and I could change it myself. All that said, It's one of those things where there is a lot of information out there..a lot of it is conflicting and each installer will have their own opinions, it's like buying a car or something. So maybe you *are* getting too wrapped up in all these technical details. The end story is as Wookey said cost vs power and remember you are tapping a free energy source so some losses here and there aren't the end of the world. As long as the system overall is making a net saving and the cost vs power ratio means it stands a chance of paying for itself at some point in the future then don't loose too much sleep. Ta Wayne

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Recovering a borked upgrade
by Mark Rogers 20 Feb '10

20 Feb '10

A little story... I decided to upgrade an Ubuntu 8.04 install to 9.10. 8.04 to 8.10 went fine. 8.10 to 9.04 broke horribly: the PC seems to have a failing fan which caused it to overheat and die mid-way through the upgrade. Surprising it booted, sort of, but when I got to the login page that died, and Alt-F1 got me to a terminal with a stream of errors stopping me doing a lot. So I booted from an Ubuntu 9.04 alternative CD, in repair mode, and got myself a command prompt chrooted to the root partition. I manually mounted the boot partition, and ran: apt-get update dpkg --configure -a apt-get update apt-get dist-upgrade .. then exited, rebooted, and got my system back fully upgraded. I didn't mention, by the way, that the system boots from a software RAID array, which "just worked". I don't expect things to work out like this when something goes horribly wrong, so it's nice to tell people when they do! (I used info from here: http://serverfault.com/questions/8540/recover-from-shutdown-during-ubuntu-d… .. to get it working.) I'm now midway through 9.04-9.10, just to prove that I haven't been put off! -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) @ 13 Clarke Rd, Milton Keynes, MK1 1LG

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External Storage
by Paul Grenyer 19 Feb '10

19 Feb '10

Hi All I'm after a couple of TBs of external storage. I've found this on eBuyer: http://www.ebuyer.com/product/168235 It doesn't mention if it's Linux compatible, any ideas how I find out? Or any suggestions for alternatives? It would be nice to have internal storage but I all the bays in my Shuttle are full and I don't know if I can run SATA drives from me IDE controller. -- Thanks Paul Paul Grenyer e: paul.grenyer(a)gmail.com b: paulgrenyer.blogspot.com

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machine ID
by Peter Alcibiades 19 Feb '10

19 Feb '10

Question: when you install some kinds of non OSS software, they generate a machine ID. You send this to the maker, they then send you back a registration code which works for that particular machine, and only that machine. Not even that machine, if you make too many changes of hardware. Is it possible to tweak a different machine so it generates the same machine ID? This is stuff that comes free with several thousand pounds worth of hardware, does something very simple, like generate a hash index of some sort on a flash card to make some standard format files accessible to the hardware. But for some crazed reason the suppliers of the hardware want to restrict the use of their stuff to one specific machine. I want to know there is a backup solution, should they go bust, or get acquired and suddenly charge exorbitant prices to move the stuff to a different machine. I am thinking, with considerable sense of humour failure, that one solution might be, install into a VM, then generate the activation for that VM, and then make an archive copy of the VM, so one would always be able to move that VM. I notice that vmware has an option for keeping the machine ID when you move installations. Which is totally ridiculous, but at least you would not have several thousand pounds worth of hardware at the mercy of a whim of some people you have never heard of somewhere in the wilds of Provence. Or their potential purchasers in Kazakhstan! Can you imagine then, you run Linux in a VM, then you run Wine in that VM, all to be able to be sure of having a moveable solution for your Windows package in case one of your machines explodes or gets stolen! Nuts. Is there a simpler way by spoofing the machine ID? Peter

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MySQL table crashes
by James Bensley 19 Feb '10

19 Feb '10

Hey List, We have a CentOS VPS with a hosting provider hosting one of our company websites. We are finding recently that about once a week a table will "crash" and needs repairing via phpMyAdmin. This is a recent development as this never used to be a problem. I wondered if any has any insight as to why this might be happening? -- Regards, James ;) Stephen Leacock - "I detest life-insurance agents: they always argue that I shall some day die, which is not so." - http://www.brainyquote.com/quotes/authors/s/stephen_leacock.html

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Sheeva and other NAS solutions
by Peter Alcibiades 19 Feb '10

19 Feb '10

Do you generally think it best to make your own file server, or just buy one ready done? I'm wondering between the following 1) Sheeva plug off ebay, and add a usb hard drive. £100 or so. 2) The Ryan Alubox, which is around £85. I am having trouble seeing why the sheevaplug is better than this. http://www.specialtech.co.uk/spshop/customer/home.php?cat=842 3) Or, we could buy the £140 Acer with FreeNAS or Clark Connect and add a usb double enclosure to it for another £40. http://www.ebuyer.com/product/167153 4) Or the Netgear dual enclosure which right now is coming with a FREE 500G drive, and it does RAID automagically if you put in a second drive, and that is around £150 http://www.ebuyer.com/product/149510 On the whole I'm inclining to the £140 Acer + usb enclosure, but I've never done this stuff before so would be really interested to hear the opinions of people who have. We do have one or two old machines lying around which we could fill up with drives, but I'm veering away from that as they are big, quite old, noisy, rather power hungry, and I am not certain of durability if running 24/7. Probably you guys have been through this and have favored solutions. Its a smallish charity with three or four computers which at the moment are only networked for printing. But we do need a simple internal web server, and we do need some central file storage, and we will have a couple of spare new 160G drives from another purchase. Peter

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Virgin (ex NTL) Broadband with Linux - how to set up?
by Chris G 19 Feb '10

19 Feb '10

My brother-in-law has a new computer with Ubuntu 9.10 installed in it, we put it together here at my house and it connected to the internet with no problems via my router here - just plugged the RJ45 in and it worked. So, basically, it's networking must be configured about right. Now he's back home and wants to connect to the internet via an NTL cable modem (now Virgin Media). The cable modem model number is NTL 250 - Model E08c007. When the RJ45 from the cable modem is plugged into his old Windows machine it works, when it's plugged into his new Ubuntu machine it doesn't work. Can anyone tell me how to get this to work? Is it a question of telling NTL/Virgin that there's a new machine (with a new MAC address) connected or does the Cable Modem expect authentication across the ethernet cable, or what? -- Chris Green

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Recommendations for Java Build Box Linux
by Paul Grenyer 19 Feb '10

19 Feb '10

Hi All I want to create myself a Java build box. Basically it requires: Java SDK Hudson TomCat Apache Webserver Ant SVN client MySQL Windows 2008 & SQL Server 2008 running on VirtualBox. All it will do is spend all day monitoring my SVN repository (which is hosted elsewhere), check out code when it changes, build the code, deploy it to TomCat and run some tests. So, VirtualBox permitting, all I think I need is a very simple server version of Linux. Any suggestions? Can I run VirtualBox on a Linux distro without a Windows manager? -- Thanks Paul Paul Grenyer e: paul.grenyer(a)gmail.com b: paulgrenyer.blogspot.com

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Site suspended?
by Chris Walker 18 Feb '10

18 Feb '10

I've just had a mail from sombeody that's trying to resubscribe to ALUG but when looking at the site, it says it's suspended with the owner being aware. Can anybody say what's going on here please as it's preventing the subscription? Thanks.

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AMD-V
by Paul Grenyer 18 Feb '10

18 Feb '10

Hi All I've recently upgraded to the latest VirtualBox (3.1.4 r57640) and want to install Windows 2008 64bit. When I try and start the VM I get the error message: "VT-x/AMD-V hardware acceleration has been enabled, but it is not operational. Your 64-bit guest will fail to detect 64-bit CPU and will not be able to boot. Please ensure that you have enabled VT-x/AMD-V properly in the BIOS of your host computer." My first thought was to disable VT-x/AMD-V for the VM just to get it going, but it gets turned on again automatically. So, of course I checked the BIOS as I was sure I had turned virtualisation on already, and yet I have and I can't see any further relevant settings. My motherboard is a GA-MA770-DS3 (F6) and I have a Phenom Quad Core 9850 processor.Do I need to upgrade the BIOS to get this to work? If so, how to I find out which revision of the board I have? The ASUS site says there are three revisions..... Any advice greatly appreciated... -- Thanks Paul Paul Grenyer e: paul.grenyer(a)gmail.com b: paulgrenyer.blogspot.com

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