Archive for the ‘trivial musing’ Category

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plug instability

Sunday, March 7th, 2010

I’m still having a variety of problems with my sheevaplug. Not least of which is the fact that SDHC cards don’t seem to be the best choice of boot medium. I have had failures with two cards now and some searching of the various on-line fora suggests that I am not alone here. In particular, SD cards seem to suffer badly under the read/write load that is routine for an OS writing log files – let alone one running a file or web server. I have also had several failures with my external USB drive. It seems that the plug boots too quickly for the USB subsystem to initialise properly. This means that there is not enough time for the relevant device file (/dev/sda1 in my case) to appear before /etc/fstab is read to mount the drive. A posting on the plugcomputer.org forum suggested a useful workaround (essentially introducing a wait), but even that was only partially sucessful. Sometimes it worked, sometimes it didn’t. In fact, the USB drive still often fails after a random (and short) time and then remounts read-only. Attempts to then remount the drive manually (after a umount) result in failure with the error message “mount: special device /dev/sda1 does not exist”.

In my attempts to cure both the booting problems and the USB connection failures I have installed the latest uboot (3.4.27 with pingtoo patches linked to from Martin’s site) and updated my lenny kernel to Martin’s 2.6.32-2-kirkwood in the (vain as it turns out) hope that the latest software would help. Here I also discovered another annoying problem – installing the latest kernel does not result in a new kernel image, the plug still boots into the old kernel until you run “flash-kernel”. Fortunately this is reasonably well known and is covered in Martin’s troubleshooting page.

I will persevere for perhaps another week with the current plug configuration. If I can’t get a stable system though I will try installing to USB drive (perverse as that may seem) and changing the uboot to boot from that rather than the flaky SD card. Most on-line advice suggests that USB support in uboot is rather “immature”, but it can’t be any worse than the current setup. My thinking is that if I can introduce a delay iin the boot process by uboot so that I can successfully boot from an external HDD, the drive connection might then be stable enough to be usable.

Of course I could be completely wrong.

Posted in electronics, linux and unix, networks and networking, tips, tricks and howtos, trivial musing | No Comments »

from slug to plug

Sunday, February 28th, 2010

Well this took rather longer than expected. I intended to write about my latest toy much earlier than this, but several things got in the way – more of which later.

About three or four weeks ago I bought myself a new sheevaplug.

image of sheevaplug

The plug has been on sale in the US for some time, but UK shipping costs added significantly to $99 US retail price. Recently however, a UK supplier (Newit) has started stocking and selling the plugs over here – and at very good prices too. My plug arrived within three days of order and I can thoroughly recommend Newit. The owner, one Jason King no less (fans of 1970’s TV will recognise the name), kept me informed of progress from the time I placed the order to the time it was shipped. He even took the trouble to email me after shipping to check that I had received it OK. Nice touch, even if it was automated.

Looking much like a standard “wall wart” power supply typically attached to an external disk, the plug is actually quite chunky, but it will still fit comfortably in the palm of your hand. Inside that little box though there is enough computing power to make a slug owner more than happy. The processor is a 1.2 GHz Marvell Kirkwood ARM-compatible device and it is coupled with 512MB SDRAM and 512MB Flash memory. Compare that to the poor old slug’s 266 MHz processor and 32 MB of flash and you can see why I’d be interested – particularly since the plug can run debian (and Martin Michlmayr has again provided a tarball and instructions to help you out.

The plugs come in a variety of flavours, but all offer at least one USB 2.0 port, a mini usb serial port, gigabit ethernet and an SDHC slot. This means that debian (or another debian based OS such as Ubuntu) can be installed either to the internal flash or to one of the external storage media available. Newit ship the plugs in various configurations and will happily sell you a device fully prepared with debian (either Lenny or Squeeze according to your taste) on SD card to go with the standard Ubuntu 9.04 in flash. Personally I chose to install debian myself, so I bought the base model. (No, I’m not a cheapskate, I just prefer to play. Where’s the fun in buying stuff that “just works”?)

Given that Martin’s instructions suggest that installing to USB disk can be problematic, and that I have debian lenny on my slugs (and had a spare 4 Gig SDHC card lying around) I chose to use his tarball to install lenny to my SDHC card. Firstly I formatted the card (via a a USB mounted card reader) as below:

/dev/sdb1 512 Meg bootable
/dev/sdb2 2.25 Gig
/dev/sdb3 1024 Meg swap

(note that the plug will see these devices as “/dev/mmcblk0pX” when the card is loaded. The “/dev/sdbX” layout simply reflects the fact that I was using a USB mounted card reader on my PC. )

I then downloaded and installed Martin’s lenny tarball to the newly formatted card and as instructed edited the /etc/fstab to match my installation. Martin’s fstab file is below:

# /etc/fstab: static file system information.
#
# proc /proc proc defaults 0 0
# Boot from USB:
/dev/sda2 / ext2 errors=remount-ro 0 1
/dev/sda1 /boot ext2 defaults 0 1
/dev/sda3 none swap sw 0 0
# Boot from SD/MMC:
#/dev/mmcblk0p2 / ext2 errors=remount-ro 0 1
#/dev/mmcblk0p1 boot ext2 defaults 0 1
#/dev/mmcblk0p3 none swap sw 0 0

As you can see it defaults to assuming a USB attached device. You need to comment out the USB boot entries and uncomment the SD/MMC entries if. like me, you are intending to boot from SD card. At this stage I also edited “/etc/network/interfaces” to change the eth0 interface from dhcp to static (to suit my network) and I changed “/etc/resolv.conf” because the default includes references to cyrius.com and a local IP address for DNS.

Before we can boot from the SD card, we have to make a few changes to the uboot boot loader configuration to stop it using the default OS on internal flash (where the factory installed Ubuntu resides). Again, Martin’s instructions are helpful here but he points to the openplug.org wiki for instructions in setting up the necessary serial connection to the plug. On my PC (running Ubuntu 8.04 LTS) I got no ttyUSB devices by default and “modprobe usbserial” did not work but “modprobe ftdi_sio vendor=0×9e88 product=0×9e8f” did work for me.

Now open a TTY session using cu thusly “cu -s 115200 -l /dev/ttyUSB1” – don’t use putty on linux, it doesn’t allow cut and paste which can be very useful if you are following on-line instructions (of course it helps if you cut and paste the right instructions). I found that booting is too fast if you have to switch on the plug and then return to a keyboard so I recommend simply leaving the terminal session open and resetting the plug with a pin or paper clip. Hit any key to interrupt the boot session, then follow Martin’s instructions for editing the uboot environment.

My plug was running v 3.4.16 of uboot, so at first I used version 3.4.27 (downloaded from plugcomputer.org) and loaded that via tftp as described by Martin, But this turmed out to be a mistake because my plug failed to boot thereafter. I got the following error message via the serial console:

## Booting image at 00400000 …
Image Name: Debian kernel
Created: 2009-11-23 17:25:02 UTC
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1820320 Bytes = 1.7 MB
Load Address: 00008000
Entry Point: 00008000
Verifying Checksum … Bad Data CRC

Some searching suggested that the uboot image was probably the problem and that reverting to v3.4.19 would solve this. So I downloaded 3.4.19 from “vioan’s” post “#6 on: November 16, 2009, 03:21:34 PM” at the plugcomputer.org forum and reflashed the plug with that image. Success – my plug now booted into debian lenny. Tidy up, update the OS and add a normal user as recommended and we’re ready to go.

My plug was intended to replace the slug I was using as my local apt-mirror. That mirror is now fairly large because I have a mix of 32 and 64 bit ubuntus (of varying vintages) and 386 and ARM versions of debian. I therefore recycled an unused 500 gig lacie USB disk and mounted that as /home2 (originally as /home, but I soon changed that when I wanted to unmount it frequently and then lost my home directory….) Copying the apt-mirror (175 Gig) over the network from my old slug was clearly going to take forever – high speed networking is not the slug’s forte, so I mounted both the slug and the plug’s disks locally on my PC and copied the files over USB – much faster. It was here that I discovered why the old lacie disk (a “designed by porsche” aluminium coated beast) was lying idle. I’d forgotten that it sounded like a harrier jump jet on take off when in use. I put up with that for a week – just long enough to get me to a free weekend when I could rebuild the old slug (now used as just an NTP server and the webcam) to boot from a 4 gig USB stick so that I could recycle its disk onto the plug. I’ve just finished doing that.

One other problem I found with the plug which caused me much head scratching (and delayed my writing this as I noted above) was that it consistently failed to boot back into my debian install after a “reboot” or “shutdown -r” – I had to power cycle the device to get it to boot properly. I spent some time this weekend with the serial port connected before I noticed (using “printenv” at the uboot prompt) that I had mixed up the uboot environment variables printed on Martin’s site. I had actually copied part of the instructions for the USB boot variant instead of the correct ones for the SD card boot. Sometimes “cut and paste” can be a mistake.

Posted in electronics, linux and unix, networks and networking, tips, tricks and howtos, trivial musing | No Comments »

homeopathy

Friday, February 26th, 2010

I can’t recall how I got there, but this made me laugh enough to want to share it.

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isp shenanigans

Saturday, February 20th, 2010

I have recently been off-line. And I am less than happy about the reasons.

My ISP recently informed me that it was changing it’s back end provider from Entanet to Vispa. Like many small ISPs, my provider does not have any real infrastructure of its own, it simply repackages services provided by a wholesaler who does have the necessary infrastructure in a process commonly called “whitelabelling”. This whitelabel approach is particularly common amongst providers of webspace and it normally works fine. Amongst the smaller ISPs there are many who are simply Entanet resellers. And until recently Entanet had a good name for pretty solid service. Well not any more.

I had not noticed any particular problems and was slightly surprised to hear from my ISP that they were unhappy with the service they were getting from Entanet. Apparently there had been frequent network outages for many of their customers and so they had chosen a new provider and were notifying their customers of impending moves, Of course this would mean some local configuration changes so customers were advised in advance of those changes and the dates for action. Apart from preparing to change the ADSL login details on my router, in my case I also had to ensure that my SSH and other login details on various external services I have or use were modified to accept the new fixed IP address assigned to my router (I tend to lock down such services so that they only accept connections from my IP address, not foolproof I know, but it all helps).

In the migration advice letter, my ISP advised its customers to set up new direct debit arrangements for VIspa and cancel the existing ones to Entanet. That letter advised that any over or under charge either way during transition would be sorted out between the providers. So I did as I was advised and waited for the big day (approximately 10 days away). Big mistake.

About a week before the date of transition I found my web traffic intercepted and blocked by Entanet with the message “Your account has been blocked. Please contact your internet service provider”. This blockage only occurred on web traffic (my email collection over POP3S and IMAPS continued to work, as did ICMP echo requests and ssh connections out). This action actually pissed me off even more than I would have been if Entanet had completely cut my connection. It also, incidentally, betrayed the fact that they were using a transparent web proxy on the connection – not something that makes me very happy. But simply blocking web traffic was obviously designed to annoy me and make me contact my ISP and strongly suggests to me that Entanet were usnsure of their legal right to cut me off completely. Further, in my view, intercepting my web traffic in this way may actually have been illegal.

Interestingly, even http traffic aimed inbound to my ADSl line (where I run a webcam on one of my slugs) was similarly intercepted as is evidenced by this link from changedetection.com. Obviously, the imposition of the message from Entanet was picked up by changedetection as an actual change to that web page.

So I emailed Entanet and my ISP, pointing out that my contract was with them and not Entanet and told them to sort it out between themselves. I, as a customer, did not expect to be penalised simply because my ISP had decided to change its wholesaler. Meanwhile, I decided to bypass Entanet’s pathetic and hugely irritating web block by tunneling out to a proxy of my own. Of course I could have used my existing tor connection, but that is not always as fast as I would like, particularly at peak web usage hours, so I set up a new proxy on another of my VPSs using tinyproxy, listening on localhost 8118 (the same as privoxy on my tor node). I then set up an ssh listener on my local machine and set firefox to use that listener as its proxy – again, much as I had for tor. Bingo. Stuff you Entanet.

Unfortunately, it did not stop there. Entanet’s rather arrogant response to my email was to insist that I re-establish a direct debit with them for the few days remaining before the changeover (despite them having had my payment in advance for the month in question). No way, so I ignored this request only to find that Entanet then throttled my connection to 0.02 Mb/s – see the speedtest result below.

speedtest image

speedtest image

This sort of speed is just about usable for text only email, but is absolutely useless for much else. Now I had originally been given two separate dates for the changeover by my ISP, so in a fit of over enthusiastic optimism on my part, I tried to convince myself that the earlier (later corrected) date given was the correct one and so I reconfigured my router in the hope it would connect to Vispa, No deal. Worse, when I then tried to fall back to the (pitiful) Entanet connection, I found it blocked completely. I was thus without a connection for some four days (including a very long weekend).

So far my new connection looks good. But apart from my disgust with Entanet, I have not been overly impressed with the support I have received from my ISP during these problems. I’ll keep an eye on things – I may yet move of my own volition.

[Addendum] just by way of comparison, the test result below is what I expect my connection speed to look like. Test run at around 21.45 on Sunday 21 February 2010.

speedtest image

That’s a bit better. Note however that this test was direct from Vispa’s network rather than through my ssh tunnel.

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are you /really/ sure you want that mobile phone?

Sunday, January 10th, 2010

The launch of the google nexus one “iPhone killer” reminds me just how prescient Dr Fun’s cartoon of 16 January 2006 (see second cartoon down from the top on the right) really was.

I just love the way the google employee in the video says at the end that Verizon and Vodafone have “agreed to join our program”.

Oh yes indeed.

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using scroogle

Saturday, January 2nd, 2010

For completeness, my post below should have pointed to the scroogle search engine which purportedly allows you to search google without google being able to profile you. Neat idea if you must use google (why?) but it still fails the Hal Roberts test of what to do if the intermediate search engine is prepared to sell your data. I actually quite like the scroogle proxy though, particularly in its ssl version because anything that upsets google profiling has to be a good thing. Besides, the really paranoid can simply connect to scroogle via tor.

(Odd that google seem not to have tried to grab the scroogle domain name. If they do, let’s just hope that they get the groovle answer.)

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scroogled

Saturday, January 2nd, 2010

One of the more annoying aspects of the web follows directly from one of its strengths. The web is actually designed to make it easy for authors to cross refer to the work of others – hyperlinking is intended to make linking between documents anywhere in web space seamless and transparent. Unfortunately, this cross linking ability leads to many posts (this one included) quoting directly from the source when referring to material elsewhere. In the academic world, quoting from source material is encouraged. When the work is properly attributed to the original author, then this is known as research. Without such attribution it is known as plagiarism.

So whenever I post or write here, I try hard to refer to original source material if I am quoting from elsewhere or I am referring to a particular tool or technique I have found useful. If I am writing about something commented on elsewhere (as for example, Hal Roberts’ discussion of GIFC selling user data in my posting about anonymous surfing), then I will try to link directly to the original material rather than to another article discussing that original. There are fairly good (and obvious) reasons for doing this, not least of which is that the original author deserves to be read directly and not through the (possibly) distorting lens of someone else’s words.

Writing for the web is a very different art to writing for print publication. Any web posting can easily become lazy as the author cross refers to other web posts. Many of those posts may be inaccurate or not primary source material. This can lead to the sort of problem commonly seen in web forums where umpteen people quote someone who said something about someone else’s commentary on topic X or Y. In such circumstances, finding the original, definitive, authoritative, source can be difficult.

Like most people, when faced with this sort of problem I resort to using one or more of the main search engines. But what to search for? Plugging in a simple quote from the original article can often bring up references to unrelated material which happens to include that same (or very similar) phrase. Worse, for reasons outlined above, the search can simply return multiple instances of postings in web fora about the article rather than the article itself. Most irritatingly these days I find that a search will lead to a wikipedia posting – and I just don’t trust the “wisdom of the crowds” enough to trust wikipedia. I’m old fashioned, I like my “facts” to be peer reviewed, authoritative, and preferably written in a form not subject to arbitrary post publication edits. Actually I still prefer dead trees as a trusted source of both factual material and fiction – which is one reason I have lost count of the number of books I have. I also like the reassuring way I can go to my bookshelf and know that my copy of 1984 will be where I left it and in a form in which I remember it.

So when I was researching older articles about Google recently and I wanted to find a copy of Cory Doctorow’s original short fiction piece about Google called “Scroogled” I expected to find umpteen thousand quotes as well as pointers to the original. I was wrong. I originally searched for the phrase “Want to tell me about June 1998?” on the grounds that that would be likely to give me a tighter set of results than simply looking for “scroogled”. This actually gave me fewer that sixty hits on clusty. I was initially reassured that most of the results were simple extracts of the full story with pointers to the original article on radaronline. Even Doctorow’s own blog points to radaronline without giving a local copy of the story. But then I discovered that radaronline no longer lists that article at that URL. Worse, a search of the site gives no results for “scroogled”. So Cory Doctorow’s creative commons licenced short has vanished from the original location and all I can find are copies. This worries me. Perhaps I’m wrong to rely on pointing to original material. What if the original is ephemeral? Or gets pulled for some reason? And if I point to copies, how can I be sure those copies are faithful to the original?

I actually fell foul of this same problem myself a couple of years ago when I was discussing my experiences with BT’s awful home hub router. I wrote in that post a reference to a contribution I made on another forum about my experiments with the FTP daemon on the hub whilst I was figuring out how to get a root shell. That article no longer exists, because the site no longer exists, and I have no copy.

So the web is both vast and surprisingly small and fragile in places.

Oh, just to be on the safe side, I have posted here a local (PDF) copy of scroogled obtained from feedbooks. You never know.

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shiny!

Wednesday, December 30th, 2009

Well I finally cracked and ordered an N900 on-line just before Christmas. Nokia had been promising since about August of this year that the device “might” ship in the UK around October. Since then, the release date has slipped, and slipped, and slipped (much to the amusement of an iPhone using friend of mine who predicted exactly that back in August). Every time I read about a new impending release date I checked with the major independent retailers only to be told “no, not yet, maybe next month”.

Many review sites are now saying that Vodafone and T-Mobile will both be shipping the N900 on contract in January. Well, not according to the local retail outlets for those networks they won’t. And besides, I had no intention of locking myself in to a two year contract at around £35-£40 pcm, particularly if the network provider chose to mess about with the device in order to “customise” it. So, as I say, I cracked and ordered one on-line, unlocked and SIM free on 21 December. It arrived yesterday, which is pretty good considering the Christmas holiday period intervened.

nokia n900

nokia n900

So what is it like?

Well, there is a pretty good (if somewhat biased) technical description on the Nokia Maemo site itself, and that site also has a pretty good gallery of images of the beast so I recommend interested readers start there. There are also a number of (sometimes breathless) reviews scattered around the net, use your search engine of choice to find some. I won’t attempt to add much to that canon here. Suffice to say that I am a gadget freak and a fan of all things linux and open source. This device is a powerful, hand held ARM computer with telephony capability – and it runs a Debian derivative of linux. What more could you ask for?

Tap the screen to open the x-terminal and you drop in to a busybox shell.

busybox shell on the N900

busybox shell on the N900

Oh the joy!

So – first things first. Add the “Maemo Extras” catalogue to the application manager menu, then Install openSSH, add a root password and also install “sudo gainroot”. Stuff you Apple, I’ve got a proper smartphone (and, moreover, one which is unlikely to be hit by an SSH bot because a) I have added my own root password, and b) I have moved the SSH daemon to a non-standard port – just because I can). Now I can connect to my N900 from my desktop, but more importantly from my N900 to my other systems. Next on the agenda is the addition of OpenVPN so that I can connect back to my home network from outside. Having the power and portability of the N900 means that even my netbook is looking redundant as a mobile remote access device.

(Oh, and it’s a pretty good ‘phone too, if a little bulky).

Posted in linux and unix, multimedia, trivial musing | No Comments »

hamster dance

Saturday, December 12th, 2009

Some years ago a website showing dancing hamsters (or “hampsters” sic) became an overnight sensation. A freelance programmer called Adam Bowman runs a blog which showcases his gadgets, one of which is a cute little hamster. In the spirit of Christmas I thought I’d post a link here.

Watch the little chap run on his wheel. You can feed him by clicking your mouse. Click the center of the wheel to make him get back on it.

(And, yes, I know this is flash based….)

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comment spam

Saturday, December 12th, 2009

I block comment spam aimed at this blog, and I insist that commenters leave some form of identification before I will allow a comment to be posted. Further, I use a captcha mechanism to keep the volume of spam down. Nevertheless, like most blogs, trivia attracts its fair share of attempted viagra ads, porn links and related rubbish. Most appears to come from Russia for some reason.

Periodically I review my spam log and clear it out – it can make for interesting, if ultimately depressing reading (when I can actually understand it). But one post today plucked at my heart strings. The poster, again from a Russian domain, said “Dear Author baldric.net ! I am final, I am sorry, but it does not approach me. There are other variants?”

I guess it lost something in the translation.

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