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Installing Debian on x86 readyNAS.

The Netgear readynas is essentially a x86 computer, with a handy Serial TTL interface at the back.

However, it’s not entirely straight forward. Unetbootin-created usb-media did not boot, but the debian netboot iso appears to boot. However, it doesn’t support serial console out of the box.

After remastering the netboot image with settings for console, I was ready to try again – holding the ‘backup’ button on front while powering up. And presto – a debian boot menu appeared. From thereon it was pretty straight forward. If you want, you can grab the image here – debian-8.2-serial.iso. It can we written to CD with your favourite recording software, or written to a usb stick with dd. For the Netgear, use a usb stick.

The performance went from 450Mbps to 950Mbps, so clearly the way outdated software that Netgear shipped it with was inadequate for the hardware.

So now I have a Debian computer, which can do anyting – not limited to what Netgear wanted me to do. And as a bonus it even performs better!

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AIS reception with RTL-SDR

Some of you may have heard about rtl-sdr, which is basically a software defined radio framework, for cheap USB sticks. The USB sticks can be picked up for 10-20$.

They’re not excellent. They have limited bandwith (~2MHz), they have noticeable noise, and they don’t have that good sensitivity. But for the price? It’s a extremely good offer.

AIS reception has been covered by the guys at I found this quite lacking, and it didn’t explain some of the stuff, like why resample the audio to 12kHz.

After fiddling around for some days, I found rtl-ais which is a modified version of rtl-sdr, with direct support for AIS decoding. It worked! Just specifying the tuner error, and it was outputting AIS messages.

However, the decoder was not that elegant, and GNUAIS had interesting features, like the ability to feed data directly to mysql.

AIS is transmitted at 161.975 and 162.025MHz, which is within the 2MHz bandwidth of the RTL-SDR sticks, so both channels can be received at once. The rtl_ais software is a modified version of rtl_fm, which can do exactly this. Feeding the output audio to a named pipe, and setting gnuais up to read from that named pipe, instead of audio card, worked just perfectly!

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Raspberry Pi as cheap media player.

CC-BY-SA 3.0 - by Jwrodgers

CC-BY-SA 3.0 – by Jwrodgers

As you may’ve guessed from some previous blog posts, I have been expirementing with Raspberry Pi as media player.

The setup was not entirely straight forward, as it was to be located at my girlfriends place, with access to the media I have at home.

I was looking at OpenVPN as solution, tying the networks together. She has ample down link (16Mb/s), and I have ample uplink (12Mb/s) to make this viable.

I started testing with my laptop as media player, and 720p played just fine from a NFS volume mounted over OpenVPN. A few glitches during playback if the connection was used for anything else whilst playing, but quite smooth and usable.

1080p, however, was no go. Low BW 1080p might work, but probably not. The solution for this was Plex, with a suitable plugin in XBMC. Plex handles on-the-fly transcoding to a more suitable bandwidth profile.

After testing a bit, my conclusion was that the solution was not performing well enough. Throughput was 2-3Mb/s over the OpenVPN-link. Originally I believed this was due to the limited CPU power of the Pi, but it turned out that the Edimax Wireless USB adapter was the culprit. When testing at home, it was placed 50cm from the antennas of my access point; not the setup at my girlfriends place. There it was 5 meters…

Changing to cabled gave a throughput of roughly what the link should be able to carry (11.5Mb/s according to Samknows), minus overhead. So actual throughput was 10.5-11Mb/s downstream, and 4.5-5Mb/s upstream, tested with iperf/.
Plex setting at 8Mb/s was working nice – if connection was not used for other stuff at same time. Right now it’s set to 4Mb/s, which leaves quite a bit of headroom for other stuff.

I run the OpenVPN in a bridged setup, to avoid routing or any such things – easier to integrate the two LAN’s in bridged mode. Performance is acceptable enough, and the added benefit is that I can use everything as if at home no matter where I am 🙂

Right now, it’s running on cable, and I’m looking for a cheap and good wireless stick, well supported by Linux…

(Oh. OpenVPN setup looks difficult, but it’s rather easy once you actually grok it. The client config file can be as short as this:

proto udp
dev tap0
ca ca.crt
cert client2.crt
key client2.key
script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

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Xbian vs. Raspbmc

CC-BY-SA 3.0 - by Jwrodgers

CC-BY-SA 3.0 – by Jwrodgers

I’ve recently tested Xbian and Raspbmc. Xbian seems to be based of raspbmc, with a few changes, for example a quite sleek setup plugin.

Raspbmc, in turn, are based on Debian, the well known Linux-distro, with apt and all the snacks.

Both are painless to setup, and works quite fine for playing media files. However, I wanted a bit of a special setup with openvpn connectivity to the NFS / Plex server. This was fairly easy to set up, apt-getting the openvpn and resolvconf packages. But with Xbian it stopped there. They use 7 year old dhcp-scripts, which has no concept of resolvconf. Why? I don’t quite understand, as Raspbmc does not. On Raspbmc the openvpn + resolvconf setup just worked.

Same goes for other things – Xbian does not show the correct time in xbmc, even though system time is set correctly. Raspbmc handled this just fine.

I’m aware that Xbian is in a beta, but they seem to have made some very strange decisions in the transition from Raspbmc…

Also Raspbmc uses less cpu for xbmc, with approx 15-16% cpu load for idle, and 80% with running full screen music visualiser. RAM usage? 150MB used with Raspbmc, 300MB+ with Xbian.

I have not checked why those differences are there. But they are, and they’re irritating enough…

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The M570 Trackball

The Logitech M570 trackball is good. If I use a normal mouse, I’ll get a stiff shoulder after a couple of days. What I can use is an clitoris or trackball. My x220 has a clitoris, which I don’t like in games.

The trackball, however, works fine in openTTD.

I’ve used various trackballs before, but the wireless of M570 is good. It meens I can sit in the sofa, without having to care about the wire. The performance is the same as previous trackballs, and I don’t really understand why a LASER is important on a trackball – the surface is known… But what goes with the territoriy…

At least – I happen to love my trackball, and it’s totally worth the price of ~100$.

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bitcoin-logo-1000_0Ok, so we have a couple of cryptocurrencies out there, bitcoin, litecoin and so on. I had a look, trying to buy some litecoins, but was utterly turned away by the hoops I have to jump…:

  • First transfer money in EUR/USD/RUR or other national valuates.
  • Buy the coins.
  • Send them.

In addition, the credit card interface was in russian, with quite a lot of options to select from – and wanted me to create a user at a separate website from the trading site. And of course there was a 3% fee, or more, involved, plus the 1.75% VISA charges for foreign valuates.

I consider myself more technologically advanced than the average – by far. Yet I’m not able to get my hands on those cryptocurrencies in an easy way.

So how do you ever expect it to be for someone not speculating, criminal or enthusiastic about it? If you’re a criminal, it offers clear benefits. If you’re speculating, their rise has been spectacular…

But as means of purchasing something? Sorry. With Paypal I enter my username and password, and press enter two times. Convenience are more important than the high ideals about anonymous, untraceable currencies. For I’m all for the latter one, but not with this horrible user experience.

And then I’ve not even mentioned the litecoin client, which downloads at least a few hundred megabytes of data, taking long time, providing little or no feedback…

It’s utterly useless as a currency or mean of payment to me right now, and I bet I’m not the only one with the same feeling…


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chdk – again.

Once again, I’ve gotten myself a Canon compact camera that can run CHDK.CHDK

Apart from some minor details, it works great. One of the stupid things is that the lens does not come out automagically when turning on camera with CHDK activated. I need to do a half press of the shutter first… OK, I can live with that, typically I use the standard firmware for point’n’shoot, and only use the CHDK when I want to do some scripting.

CHDK is fun as always. Easy to do new things, quite easy to create your own scripts. But I’m a bit flustered – there is not very much documentation on some functions – how to check if camera has aquired a good autofocous for instance? I don’t know if this is problems with the camera hw, or bad documentation from CHDK’s side.

Anyway, its entertaining to be able to script my camera, and with a gorilla pod, AC adapter from ebay, and 4GB memory card, thet total price is around 220$ for the package. Unbeatable amount of fun for that money 🙂

The possibilities are nearly endless:

  • Raw photos from a compact camera.
  • Motion detection.
  • Zebra striping of under/over exposed areas before taking a photo.
  • Greater manual control over camera.

The list goes on, and their FAQ explains it quite well.

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Nordmann for Al Qaeda?

NRK skriv at ein nordmann er trent av Al Qaeda. Der kan ein lese følgande gullkorn:

Den 33-årige etnisk norske mannen som har konvertert til islam, har plettfritt rulleblad, norsk utseende og regnes som en stor potensiell fare dersom han er trent, operativ og klar til å begå terrorhandlinger mot et vestlig mål, som for eksempel et sivilt passasjerfly.

Dette fordi han regnes for å gå under «radaren» på grunn av upåfallende utseende og fortid, og dermed svært vanskelig å plukke ut som potensiell terrorist.

Det tyder i så fall på at svært mange av sikringstiltaka er sikkerhetsteater, og lite anna. For ser du etter skjeggete muslimer så rekruterer Al Qaeda blonde nordmenn.

Men fyren vart jo plukka opp av etteretning, og har vel neppe sjans til å settje seg på eit fly utan å bli grundig sjekka neste gong?

Om antiterrorsystema våre antar at terrorister er skjeggete muslimer er det problemet.

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Quick and dirty download proxy

fget is a small, quick and dirty download proxy in php and python, to be used on a webserver to allow it to download files to the webserver, and allow access to them.

Written for personal use when travelling, and on various bad links.
License? Buy me a beer next time you see me if it is useful.

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Bypassing liquid ban with help from KLM

I recently flew with KLM from Singapore to Amsterdam. They have this tradition of giving you small houses filled with jenever.

Thats just fine, but the problem is that they are filled with liquid, and above 100ml. So you have to have them in a sealed bag through security if you have a connecting flight.

KLM’s solution? Hand out a sealable bag, a card stating at which flight it was received, and date. The card was quite simple, with no serial numbers, no stamp, no signature. Just the flight numbers.

I got the bag and card after the house, and was told to seal it myself! I just ignored both, the house was quite ugly after all, and a bit of jenever is not worth carrying for me…

However, it is quite nice of KLM to hand out unsealed bags… Just another dent in the airport security?

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