Search Results: "leist"

12 May 2020

Evgeni Golov: Building a Shelly 2.5 USB to TTL adapter cable

When you want to flash your Shelly 2.5 with anything but the original firmware for the first time, you'll need to attach it to your computer. Later flashes can happen over the air (at least with ESPHome or Tasmota), but the first one cannot. In theory, this is not a problem as the Shelly has a quite exposed and well documented interface: Shelly 2.5 pinout However, on closer inspection you'll notice that your normal jumper wires don't fit as the Shelly has a connector with 1.27mm (0.05in) pitch and 1mm diameter holes. Now, there are various tutorials on the Internet how to build a compatible connector using Ethernet cables and hot glue or with female header socket legs, and you can even buy cables on Amazon for 18 ! But 18 sounded like a lot and the female header socket thing while working was pretty finicky to use, so I decided to build something different. We'll need 6 female-to-female jumper wires and a 1.27mm pitch male header. Jumper wires I had at home, the header I got is a SL 1X20G 1,27 from reichelt.de for 0.61 . It's a 20 pin one, so we can make 3 adapters out of it if needed. Oh and we'll need some isolation tape. SL 1X20G 1,27 The first step is to cut the header into 6 pin chunks. Make sure not to cut too close to the 6th pin as the whole thing is rather fragile and you might lose it. SL 1X20G 1,27 cut into pieces It now fits very well into the Shelly with the longer side of the pins. Shelly 2.5 with pin headers attached Second step is to strip the plastic part of one side of the jumper wires. Those are designed to fit 2.54mm pitch headers and won't work for our use case otherwise. jumper wire with removed plastic As the connectors are still too big, even after removing the plastic, the next step is to take some pliers and gently press the connectors until they fit the smaller pins of our header. Shelly 2.5 with pin headers and a jumper wire attached Now is the time to put everything together. To avoid short circuiting the pins/connectors, apply some isolation tape while assembling, but not too much as the space is really limited. Shelly 2.5 with pin headers and a jumper wire attached and taped And we're done, a wonderful (lol) and working (yay) Shelly 2.5 cable that can be attached to any USB-TTL adapter, like the pictured FTDI clone you get almost everywhere. Shelly 2.5 with full cable and FTDI attached Yes, in an ideal world we would have soldered the header to the cable, but I didn't feel like soldering on that limited space. And yes, shrink-wrap might be a good thing too, but again, limited space and with isolation tape you only need one layer between two pins, not two.

6 November 2017

Jonathan Dowland: Coil

Peter Christopherson and Jhonn Balance, from [Santa Sangre](https://santasangremagazine.wordpress.com/2014/11/16/the-angelic-conversation-in-remembrance-of-coil/) Peter Christopherson and Jhonn Balance, from Santa Sangre
A friend asked me to suggest five tracks by Coil that gave an introduction to their work. Trying to summarize Coil in 5 tracks is tough. I think it's probably impossible to fairly summarize Coil with any subset of their music, for two reasons. Firstly, their music was the output of their work but I don't think is really the whole of the work itself. There's a real mystique around them. They were deeply interested in arcania, old magic, Aleister Crowley, scatology; they were both openly and happily gay and their work sometimes explored their experiences in various related underground scenes and sub-cultures; they lost friends to HIV/AIDS and that had a profound impact on them. They had a big influence on some people who discovered them who were exploring their own sexualities at the time and might have felt excluded from mainstream society. They frequently explored drugs, meditation and other ways to try to expand and open their minds; occultism. They were also fiercely anti-commercial, their stuff was released in limited quantities across a multitude of different music labels, often under different names, and often paired with odd physical objects, runes, vials of blood, etc. Later fascinations included paganism and moon worship. I read somewhere that they literally cursed one of their albums. Secondly, part of their "signature" was the lack of any consistency in their work, or to put it another way, their style over time varied enormously. I'm also not necessarily well-versed in all their stuff, I'm part way on this journey myself... but these are tracks which stand out at least from the subset I've listened to. Both original/core members of Coil have passed away and the legal status of their catalogue is in a state of limbo. Some of these songs are available on currently-in-print releases, but all such releases are under dispute by some associate or other.

1. Heaven's Blade Like (probably) a lot of Coil songs, this one exists in multiple forms, with some dispute about which are canonical, which are officially sanctioned, etc. the video linked above actually contains 5 different versions, but I've linked to a time offset to the 4th: "Heaven's Blade (Backwards)". This version was the last to come to light with the recent release of "Backwards", an album originally prepared in the 90s at Trent Reznor's Nothing Studios in New Orleans, but not finished or released. The circumstances around its present-day release, as well as who did what to it and what manipulation may have been performed to the audio a long time after the two core members had passed, is a current topic in fan circles. Despite that, this is my preferred version. You can choose to investigate the others, or not, at your own discretion.

2. how to destroy angels (ritual music for the accumulation of male sexual energy) A few years ago, "guidopaparazzi", a user at the Echoing the Sound music message board attempted to listen to every Coil release ever made and document the process. He didn't do it chronologically, leaving the EPs until near the end, which is when he tackled this one (which was the first release by Coil, and was the inspiration behind the naming of Trent Reznor's one-time side project "How To Destroy Angels"). Guido seemed to think this was some kind of elaborate joke. Personally I think it's a serious piece and there's something to it but this just goes to show, different people can take things in entirely different ways. Here's Guido's review, and you can find the rest of his reviews linked from that one if you wish. https://archive.org/details/Coil-HowToDestroyAngels1984

3. Red Birds Will Fly Out Of The East And Destroy Paris In A Night Both "Musick To Play In The Dark" volumes (one and two) are generally regarded as amongst the most accessible entry points to the Coil discography. This is my choice of cut from volume 1. For some reason this reminds me a little of some of the background music from the game "Unreal Tournament". I haven't played that in at least 15 years. I should go back and see if I can figure out why it does. The whole EP is worth a listen, especially at night. https://archive.org/details/CoilMusickToPlayInTheDarkVol1/Coil+-+Musick+To+Play+In+The+Dark+Vol+1+-+2+Red+Birds+Will+Fly+Out+Of+The+East+And+Destroy+Paris+In+A+Night.flac

4. Things Happen It's tricky to pick a track from either "Love's Secret Domain" or "Horse Rotorvator"; there are other choices which I think are better known and loved than this one but it's one that haunted me after I first heard it for one reason or another, so here it is.

5. The Anal Staircase Track 1 from Horse Rotorvator. What the heck is a Horse Rotorvator anyway? I think it was supposed to have been a lucid nightmare experienced by the vocalist Jhonn Balance. So here they wrote a song about anal sex. No messing about, no allusion particularly, but why should there be? https://archive.org/details/CoilHorseRotorvator2001Remaster/Coil+-+Horse+Rotorvator+%5B2001+remaster%5D+-+01+The+Anal+Staircase.flac

Bonus 6th: 7-Methoxy-B-Carboline (Telepathine) From the drone album "Time Machines", which has just been re-issued by DIAS records, who describe it as "authorized". Each track is titled by the specific combination of compounds that inspired its composition, supposedly. Or, perhaps it's a "recommended dosing" for listening along. https://archive.org/details/TimeMachines-TimeMachines

Post-script If those piqued your interest, there's some decent words and a list of album suggestions in this Vinyl Factory article. Finally, if you can track them down, Stuart Maconie had two radio shows about Coil on his "Freak Zone" programme. The main show discusses the release of "Backwards", including an interview with collaborator Danny Hyde, who was the main person behind the recent re-issue. The shorter show is entitled John Doran uncoils Coil. Guest John Doran from The Quietus discusses the group and their history interspersed with Coil tracks and tracks from their contemporaries. Interestingly they chose a completely different set of 5 tracks to me.

26 April 2016

Matthias Klumpp: Why are AppStream metainfo files XML data?

This is a question raised quite quite often, the last time in a blogpost by Thomas, so I thought it is a good idea to give a slightly longer explanation (and also create an article to link to ). There are basically three reasons for using XML as the default format for metainfo files: 1. XML is easily forward/backward compatible, while YAML is not This is a matter of extending the AppStream metainfo files with new entries, or adapt existing entries to new needs. Take this example XML line for defining an icon for an application:
<icon type="cached">foobar.png</icon>
and now the equivalent YAML:
Icons:
  cached: foobar.png
Now consider we want to add a width and height property to the icons, because we started to allow more than one icon size. Easy for the XML:
<icon type="cached" width="128" height="128">foobar.png</icon>
This line of XML can be read correctly by both old parsers, which will just see the icon as before without reading the size information, and new parsers, which can make use of the additional information if they want. The change is both forward and backward compatible. This looks differently with the YAML file. The foobar.png is a string-type, and parsers will expect a string as value for the cached key, while we would need a dictionary there to include the additional width/height information:
Icons:
  cached: name: foobar.png
          width: 128
          height: 128
The change shown above will break existing parsers though. Of course, we could add a cached2 key, but that would require people to write two entries, to keep compatibility with older parsers:
Icons:
  cached: foobar.png
  cached2: name: foobar.png
          width: 128
          height: 128
Less than ideal. While there are ways to break compatibility in XML documents too, as well as ways to design YAML documents in a way which minimizes the risk of breaking compatibility later, keeping the format future-proof is far easier with XML compared to YAML (and sometimes simply not possible with YAML documents). This makes XML a good choice for this usecase, since we can not do transitions with thousands of independent upstream projects easily, and need to care about backwards compatibility. 2. Translating YAML is not much fun A property of AppStream metainfo files is that they can be easily translated into multiple languages. For that, tools like intltool and itstool exist to aid with translating XML using Gettext files. This can be done at project build-time, keeping a clean, minimal XML file, or before, storing the translated strings directly in the XML document. Generally, YAML files can be translated too. Take the following example (shamelessly copied from Dolphin):
<summary>File Manager</summary>
<summary xml:lang="bs">Upravitelj datoteka</summary>
<summary xml:lang="cs">Spr vce soubor </summary>
<summary xml:lang="da">Filh ndtering</summary>
This would become something like this in YAML:
Summary:
  C: File Manager
  bs: Upravitelj datoteka
  cs: Spr vce soubor 
  da: Filh ndtering
Looks manageable, right? Now, AppStream also covers long descriptions, where individual paragraphs can be translated by the translators. This looks like this in XML:
<description>
  <p>Dolphin is a lightweight file manager. It has been designed with ease of use and simplicity in mind, while still allowing flexibility and customisation. This means that you can do your file management exactly the way you want to do it.</p>
  <p xml:lang="de">Dolphin ist ein schlankes Programm zur Dateiverwaltung. Es wurde mit dem Ziel entwickelt, einfach in der Anwendung, dabei aber auch flexibel und anpassungsf hig zu sein. Sie k nnen daher Ihre Dateiverwaltungsaufgaben genau nach Ihren Bed rfnissen ausf hren.</p>
  <p>Features:</p>
  <p xml:lang="de">Funktionen:</p>
  <p xml:lang="es">Caracter sticas:</p>
  <ul>
  <li>Navigation (or breadcrumb) bar for URLs, allowing you to quickly navigate through the hierarchy of files and folders.</li>
  <li xml:lang="de">Navigationsleiste f r Adressen (auch editierbar), mit der Sie schnell durch die Hierarchie der Dateien und Ordner navigieren k nnen.</li>
  <li xml:lang="es">barra de navegaci n (o de ruta completa) para URL que permite navegar r pidamente a trav s de la jerarqu a de archivos y carpetas.</li>
  <li>Supports several different kinds of view styles and properties and allows you to configure the view exactly how you want it.</li>
  ....
  </ul>
</description>
Now, how would you represent this in YAML? Since we need to preserve the paragraph and enumeration markup somehow, and creating a large chain of YAML dictionaries is not really a sane option, the only choices would be: In both cases, we would loose the ability to translate individual paragraphs, which also means that as soon as the developer changes the original text in YAML, translators would need to translate the whole bunch again, which is inconvenient. On top of that, there are no tools to translate YAML properly that I am aware of, so we would need to write those too. 3. Allowing XML and YAML makes a confusing story and adds complexity While adding YAML as a format would not be too hard, given that we already support it for DEP-11 distro metadata (Debian uses this), it would make the business of creating metainfo files more confusing. At time, we have a clear story: Write the XML, store it in /usr/share/metainfo, use standard tools to translate the translatable entries. Adding YAML to the mix adds an additional choice that needs to be supported for eternity and also has the problems mentioned above. I wanted to add YAML as format for AppStream, and we discussed this at the hackfest as well, but in the end I think it isn t worth the pain of supporting it for upstream projects (remember, someone needs to maintain the parsers and specification too and keep XML and YAML in sync and updated). Don t get me wrong, I love YAML, but for translated metadata which needs a guarantee on format stability it is not the ideal choice. So yeah, XML isn t fun to write by hand. But for this case, XML is a good choice.

28 June 2013

Daniel Leidert: Idea: A new toy (ein neues Spielzeug) ... HP Microserver N54L

Ich fertige regelm ig Backups meiner Systeme an. Diese werden auf der Systemplatte meines Notebooks abgelegt und via rsync auf mobilen Speicher dupliziert. Hierzu verwende ich eine USB-Festplatte. Diese enth lt auch Medien-Dateien und wird regelm ig an den Fernseher angeschlossen. Prinzipiell halte ich meine Daten daher f r sicher. Aber vor kurzem stie ich an die Grenzen ihrer Kapazit t. Schon l nger habe ich nach einer Alternative gesucht, nicht zuletzt da heute viel gr ere Festplatten m glich sind und mein Laptop ber einen eSATA-Anschluss verf gt, der schneller als USB2.0 ist. Meine bevorzugte Variante war ein FANTEC DB-ALU3e Geh use mit einer WD Red WD20EFRX 2TB (5400 RPM) Festplatte, die f r den 24/7 Betrieb zertifiziert ist (und zudem ber eine ausgezeichnete Reputation verf gt). Die Kombination lief sehr gut und schnell, sieht edel aus, ben tigt aber eine externe Stromversorgung. Ich kann Sie als Speicherl sung absolut empfehlen. Allerdings hatte ich zu diesem Zeitpunkt noch weitere Anspr che, die mit der o.g. L sung nicht zu befriedigen sind. So trage ich mich bereits l nger mit dem Gedanken an ein RAID-1-NAS. Au erdem spiegelt sich die Beanspruchung meiner Notebook-Festplatte durch das Pakete-Bauen f r Debian im S.M.A.R.T.-Status wieder. Daher wollte ich diese Arbeit an einen robusten lokalen buildd-Boliden abgeben und habe ber den Kauf eines g nstigen Rechners nachgedacht. Ein NAS verbraucht aber deutlich weniger Strom als ein Desktop-Rechner. Also wie l sst sich ein buildd und ein energiesparendes NAS vereinen? Per Zufall stie ich bei einem lokalen H ndler auf den HP ProLiant MicroServer N40L. Das Angebot klang super und so entschied ich mich zum Kauf meines neuen Spielzeuges: ein HP ProLiant MicroServer N54L, der zuk nftig folgende Aufgaben verrichten soll:
Datensicherung
Die Sicherung der Daten erfolgt cron-gesteuert auf den RAID-Verbund in eine gesonderte (verschl sselte) Partition. Der S.M.A.R.T.-Status der Festplatten wird via smartd berwacht. Sollte eine Platte kaputt gehen, bestehen gute Aussichten, die Daten zu retten. Eine zuk nftige Option w re auch noch ein RAID-6 Verbund.
NAS / File-Server
Das Ger t verf gt ber bis zu 6 SATA Anschl sse. Davon werden vier standardm ig via Wechselrahmen belegt. Die mitgelieferte 250GB Festplatte wird vorerst das Betriebssystem aufnehmen und an den drei verbleibenden Anschl ssen werden zun chst drei WD Red WD20EFRX 2TB (5400 RPM) Festplatten als RAID-5-Verbund f r den notwendigen Platz sorgen. Letzterer l sst sich ohne Erweiterung nur via Software-Raid und mdadm realisieren.
buildd
Betriebssystem wird Debian GNU/Linux. Der Hauptspeicher wird auf mindestens 8GB ECC-Ram aufger stet.
HTPC (XBMC)
Der Microserver l sst sich nicht als Massenspeicher an einen Fernseher anschlie en. Daher soll vorr. XBMC in Verbindung mit einem USB3.0 BR/DVD-Player den Server zum Entertainment-Ger t erheben.
Das ganze soll m glichst wenig Strom verbrauchen und leise sein. Zum Anschluss an das lokale Netzwerk habe ich mich f r WLAN entschieden, da kein Gigabit-Ethernet vorhanden ist. Folgende Teile ben tige ich f r "meinen" Server:
Server
HP ProLiant N54L MicroServer mit Turion II Neo 2,2 GHz, 2GB RAM/250GB HDD - ca. 200 EUR (lokal)
Bel ftung / Lautst rke
Scythe Slip Stream Geh usel fter 120mm 800RPM 11dB - ca. 9 EUR (SY1225SL12L)
Scythe Slip Stream Geh usel fter 120mm 500RPM 7,5dB - ca. 8 EUR (SY1225SL12SL)
Netzwerk
TP-Link TL-WN722N(C) 150Mbps USB-Adapter - ca. 15 EUR (TL-WN722N(C))
File-Server
3x WD Red WD20EFRX 2TB 5400 RPM SATA600 f r NAS 24/7 - ca. 95 EUR / St. (WD20EFRX)
buildd
8GB (2x4GB) Kingston ValueRAM DDR3-1333 CL9 ECC Modul RAM-Kit - ca. 85 EUR (KVR1333D3E9SK2/8G)
16GB (2x8GB) Kingston ValueRAM DDR3-1333 CL9 ECC Modul RAM-Kit - ca. 145 EUR (KVR1333D3E9SK2/16G)
HTPC
Sapphire Radeon HD 5450/6450/6570/6670/7750 PCIe 16x Low-Profile passiv/aktiv - ca. 25..100 EUR (11166-45-20G, 11190-09-20G, 11191-27-20G, 11191-02-20G, 11192-18-20G, 11202-10-20G)
SILVERSTONE PCIe 1x USB3.0 2xInt 2xExt - ca. 21 EUR (SST-EC04-P)
Logitech K400 od. Keysonic ACK-540RF - ca. 40 EUR (920-003100 bzw. ACK-540 RF)
BR/DVD-Player od. Brenner mit USB3.0 Anschluss - 50..100 EUR
LCD-Mod
LDC Display Modul mind. 4x20 - ca. 10 EUR
Interessant ist auch noch die Option einer echten RAID-Karte. Ich stie dabei auf die IBM ServeRAID M1015 (46M0831) und diesen Hinweis. Kauft man stattdessen den "Schl ssel" zur Freischaltung des vollen Funktionsumfanges, dann bezahlt man (lokal) zus tzlich ca. 150 EUR! Aber das nur BTW. N tzliche Links:

2 October 2012

Russell Coker: Asperger Syndrome Disability vs Over Pathologising

Is Asperger Syndrome a Disability? Some people tell me that I m disabled. Usually it s an unstated implication such as referring to Asperger Syndrome as a disability with the assumption that I ll agree. One time I had someone assume that I had never had a paid job because they knew I m an Aspie, maybe I should boast more about my career successes. One interesting take on this is represented by Maco s bost about Disablism/Ablism where she says Vocab note: A person has an impairment. Society s treatment of that impairment is what disables the person [1]. The same concept is presented by BRAINHE in their Social Model of Disability document [2]. The Wikipedia page on Ableism says The ableist worldview holds that disability is an error, a mistake, or a failing, rather than a simple consequence of human diversity, akin to race, ethnicity, sexual orientation or gender [3]. This is fairly close to the position that Neurodiversity [4] advocates take on Autism. Jaarsma P and Welin S wrote an interesting paper titled Autism as a Natural Human Variation: Reflections on the Claims of the Neurodiversity Movement [5] which considers these issues in depth and comes to the conclusion that High Functioning Autism (for which Asperger Syndrome is generally regarded as a synonym) is a difference while Low Functioning Autism is a disability. I think that generally we should accept the opinion of the person in question. Someone who is unable to communicate or is too young to make an informed decision could have their disability status determined by carers. But anyone who is capable of making an informed decision and communicating it should have their opinion respected. I am not going to argue with any of the people who claim that they are disabled due to an Autism Spectrum Disorder. But I don t think that I am disabled and I think that people shouldn t argue with me about this. Over Pathologising Lynne Soraya wrote an interesting article for Psychology Today about one aspect of the supposed over-diagnosis [6]. She responds to Paul Steinberg, a psychiatrist who made a number of claims about Asperger Syndrome which lack evidence. Paul s main idea seems to be that anyone who has social problems but who seems to be successful regardless shouldn t have an Autism Spectrum diagnosis and he claims that such people should be regarded as having a social disability instead. His main idea seems to be that having a diagnosis is a bad thing, but his idea of having a social disability diagnosis instead doesn t seem so great. In many other discussions I ve seen people claim that a large number of diagnosis of anything is a problem. Their idea seems to be that the vast majority of the population shouldn t have a diagnosis for anything and that whenever a significant number of people are diagnosed with a psychological condition (and 1% of the population seems to be a significant number) then it s a problem. I don t think that having a large portion of the population diagnosed is necessarily a problem, I think that it would be OK if the majority of the population was diagnosed with something. The issue is not whether people are diagnosed but what happens after the diagnosis. When a child is diagnosed their parents can help them deal with whatever the issues are this may or may not require further involvement with psychologists or special schools. For the milder cases (of Autism, ADHD, and other conditions) merely knowing what areas will cause difficulty and teaching kids how to deal with them will be enough to solve many problems. When someone is diagnosed as a child but doesn t have obvious symptoms as an adult that is more likely to be an indication that they were taught good coping mechanisms and protected from bad situations as a child not that the diagnosis was wrong. There are some serious issues with special schools and psychiatric drugs, but diagnosis doesn t necessarily imply mistreatment and avoiding a diagnosis is not the correct way to avoid such mistreatment. When someone is diagnosed as an adult they have to learn to deal with it. The general lack of psychologists (waiting times as long as 6 months are common) and the fact that most psychologists won t do any good for someone on the Autism Spectrum is a real problem. But merely knowing the source of your problems is a major step towards alleviating or solving them. One of the arguments that is commonly used against so-called over-diagnosis is that adults don t show apparent symptoms. The issue here is that with some effort and planning adults on the spectrum can act like NTs. Acting like an NT doesn t imply being an NT, it usually requires a lot of ongoing effort that could be applied to other things if society didn t expect us to act like NTs all the time. Conclusion I wish people would stop telling me that I m either disabled or too high functioning to be on the Autism Spectrum. I will never think like an NT and I don t want to, so I ll always be an Aspie. By most objective measures I m at least as successful as the general population in all things that require social skills, so unless something like always losing at Poker is considered a disability I don t think that it s reasonable to consider me to be disabled. It would be nice if I could lock the people who claim that Autism is always a disability in a room with the people who think it s over-diagnosed and let them debate it, no matter which side lost the debate the result would be good! Update: I removed a broken link to a Youtube video, I published this post from a 3G connection and didn t test that the Youtube link still worked. For some reason the author had marked it private since the last time I visited it. Related posts:
  1. Autism vs Asperger Syndrome Diagnostic Changes for Autism Spectrum Disorders Currently Asperger Syndrome (AS)...
  2. Is Asperger Syndrome a Good Thing? A meme that keeps going around is that Asperger Syndrome...
  3. Autism Awareness and the Free Software Community It s Autism Awareness Month April is Autism Awareness month, there...

14 October 2011

Martin F. Krafft: Deutsche Bahn frequent traveller: a joke!

It has been a while since I last ranted about the Deutsche Bahn, our national train service monopoly. Out of necessity, I ve since become one of their frequent travellers. Together with the spiffy, silver card, I received a pamphlet, in which the advantages of frequent travellers are listed. When I compare those advantages to what was promised, I cannot help but notice quite a few differences to my disadvantage. Since I refused to believe that the Deutsche Bahn could be this stupid, I double-checked with the service hotline, and I now have the information to report:
  1. While the website promises free access to DB lounges for two , the pamphlet clarifies this: free access to DB lounges for you and your partner, provided each of you owns a first-class, long-distance ticket. What they left out: Oh, you don t need the frequent traveller status for that, the ticket suffices. Or, put differently: the frequent traveller status does not give you any access to the lounges. False advertising, anyone?
  2. The pamphlet explains that there are special seat areas reserved for frequent travellers. However, one must not be a frequent traveller to use them. So should I expect people to prompt me to show my card or clear my seat. And should I be expected to prompt people to flash the card or leave? Not feasible, anyone?
  3. I am told that I get priority treatment at the counter, except there is only one counter (in Munich), usually with a line of people for 1st-class and frequent travellers. All other travellers get delegated to 12 counters by an efficient number system, which means one is better off picking a number and standing in line. The other day, a lady came and flashed her frequent traveller card, expecting people to make way, but obviously noone did. Did they actually think about this, anyone?
I don t need to go into detail on the other benefits : they claim that there is special, reserved parking, but that s probably only on paper. They claim reductions in hotels and rental cars, but probably limited to availability, they claim exclusive events, but those are likely the ones noone goes to anyway. And they claim a service hotline, but it s a premium-rate number. So all in all, Deutsche Bahn have once again managed to disappoint. The frequent traveller card does not give any benefits. It rather makes me regret having spent so much money on this company. Scratch frequent traveller , make it repeat idiot . NP: Steven Wilson: Grace for Drowning

1 January 2011

Stephan Peijnik: ISC dhcpd and IP assignments from a pool to specific hosts only

Assigning an IP address statically to a host with a given MAC address using ISC dhcpd is quite trivial, one host entry, a hardware ethernet entry and a fixed-address entry and you are up and running.
But what if you want to assign IP addresses from a pool to only a few hosts with specific MAC addresses?

Before you ask yourself why someone might want to do that, have a look at my (very real) use-case.
I am currently working on setting up an installation server for my employer, ANEXIA Internetdienstleistungs GmbH. The server itself uses PXE, TFTP and FAI for installing systems. To be able to do PXE booting one has to set up an DHCP server to provide configuration details, like the TFTP Server Address and the boot filename.

Now what one should consider is that this system is designed to provide automatic installations for internet-facing hosts, namely ones in public IP networks. Running a DHCP server in such a network is not a good idea. We neither want to dish out configurations to each and every hosts that asks for them, neither do not want to do a PXE boot each and every time one of our systems is restarted. Now the combination of FAI and pxelinux allows for default configurations which force local booting, but this still causes the (re-)boot time for those systems to increase and potentially also increases the load on the TFTP server. Also, let's not even consider thinking about whether this setup is "clean" or not. I personally believe that dishing out IP addresses in a public IP network is a bad thing(tm) and I guess a lot of people will be nodding when reading these lines.

What I was asking myself is how to get something like that set up in a cleaner way, and guess what, I found a solution.
The basic idea behind this is only providing IP configuration via DHCP to a specific set of hosts (with a specific set of MAC addresses) and not providing any information to all other hosts. The specific set of hosts are those that we want to do an install run on. This is a no-brainer and I guess the right way to do that, but implementing this approach is not as straight-forward as I initially thought.

Actually the implementation of that idea caused me a bit of a headache and cost me a few work-hours to get right, that's why I'd like to share the configuration details with you.



Let's have a look at how to get such a setup using ISC dhcpd. We are using the fact that ISC dhcpd allows you to not only configure a subnet, but rather also pools inside subnets, which can have allow and deny rules. Such rules can be in the form of "allow/deny member of <class>", where classes (and subclasses, keep on reading for details) can be defined inside the configuration file as well.</class>

What we first did was creating a subnet with a pool declaration, as follows:
subnet 10.0.0.0 netmask 255.255.255.0
option routers 10.0.0.254;
option broadcast-address 10.0.0.255;
filename "fai/pxelinux.0";
next-server 10.0.0.254;
server-name "10.0.0.254";
pool
allow members of "install";
range 10.0.0.10 10.0.0.230;
This one configures the subnet 10.0.0.0/24, with 10.0.0.254 being the network gateway, 10.0.0.254 being the TFTP server and "fai/pxelinux.0" being the TFTP filename. Additionally pool allows us to define a range of IP addresses we want to use, along with a line stating that only members of the "install" class should get a network configuration. If you do not have any other subnet defined in your config and a client that is not in this "install" class asks for an IP address you will see something like this in your syslog: "dhcpd: DHCPDISCOVER from 11:22:33:44:55:66 via eth1: network 10.0.0/24: no free leases". dhcpd will not even answer these requests and thus the client will not even know that there is a DHCP server running here. Exactly what we wanted.

I wrote about this giving me a headache, but so far things have been pretty straight-forward. Getting this far did not take very long, believe me.

Next thing we did was defining that "install" class as follows:

class "install" match hardware;
Again, not very hard to do. This tells dhcpd to look for subclasses of "install" with a matching hardware-address. So let's have a look at the subclass for, let's say the host with MAC address "11:22:33:44:55:66":

subclass "install" 1:11:22:33:44:55:66;
I intentionally highlighted the leading "1:" there. This means nothing more or less than "ethernet". Without that leading "1:" you won't get anywhere. Matching will fail, simple as that. It took me a while to find information about this in "man 5 dhcp-eval". Quoting parts of the interesting section:

The hardware operator returns a data string whose first element is
the type of network interface indicated in packet being considered,
and whose subsequent elements are client s link-layer address. [...] Hardware types include ethernet (1), token-ring (6), and fddi (8).
Now, with the combination of the subnet, pool, class and subclass directives we could get the setup we wanted: a DHCP server only providing IP configuration to a specific set of hosts and ignoring all other DHCP requests.

If you have any comments about this setup or ideas on how to get something similar set-up using another approach feel free to leave a comment.

Personal final note: accidentally typing 80 instead of 08 in a MAC address will cost you an additional two hours and will even have you re-compile ISC dhcpd with eval debugging turned on, believe me. :-)

19 March 2009

Michael Banck: 19 Mar 2009

My experience with LapStore's used-ThinkPad warranty repair service My ThinkPad T40 arrived back from warranty repair today (well, actually yesterday, but I had to run off to the Gnome-2.26 release get-together in Munich so I did not have time to open the box then). I bought it used roughly two years ago at LapStore when my R51 had died. I had bought the R51 new with a one year IBM warranty but unfortunately within two years the graphics chip with got damaged and would freeze the notebook after a couple of minutes. I then decided that I do not really need a new notebook anymore, and opted for a used T4x series (there were no used X40s available at that time). I chose LapStore because they offered a one-year "Garantie" (guarantee? warranty?), which was rather unusual for used notebooks - at best, you would get a one-year "Gewaehrleistung" which is the promise to fix things which were supposedly broken already by delivery. Even better, one could optionally extend the warranty to two years, which I did. The notebook they sent was in pretty good condition (apparently a business out-of-warranty return) and I put in my R51's hard disk, the ipw2100 WLAN card and the RAM (unfortunately, I realized too late that the keyboard and the CDRW/DVD drive do not fit). I was pretty happy with it (and LapStore in general, I recommended it to a couple of friends since, and e.g. my current flatmate bought a T42 there a while ago as well) until the fan started dropping out and making weird noises by the end of 2008. So just before the end of warranty, I sent it (after removing hard disk, optical drive and battery) in to LapStore to see how their service is. I also mentioned a clear bright spot on the display (apparently some fatigue, you see it often mentioned in ThinkPad eBay descriptions) and a crack in the palmrest between the cursor-right key and the hard disk slot. When they sent a mail that the ThinkPad had arrived at their site, I also followed-up via mail that the "indestructible" keyboard caps stickers they used to mod a Scandinavian(?) keyboard into a German one were pretty much destroyed by now and would also need servicing. I assumed that they would service the fan (which looked like a clear-cut warranty issue to me) without arguing, but probably not the display and palmrest (and did not know whether they got the mail about the keyboard stickers), so when they sent another mail two days ago that they sent the notebook back without asking further questions, I became worried about what happened at all. So, long story short, I was totally positively surprised when I opened the box today and read: "Aktion: L fter, Display, Palmrest und Tastatur getauscht" (action: fan, display, palmrest and keyboard replaced) The replacements are still used parts (and the keyboard is still not a real German one, but one with new stickers on it), but they basically changed my almost-totally-broken-will-fall-apart T40 back into a almost-as-good-as-new T40. (not sure whether that is positive or negative, but they also forgot to remove the service-hard disk they put in to test things, I guess I will send it back to them) So all in all, I am very much impressed by their service. I would have expected this kind of service from IBM/Lenovo if I had a manufacturer warranty, but not from some random sell-used-ThinkPads shops on the net. I can now even more strongly recommend LapStore as the place to buy good notebooks. Certainly you can get cheaper prices at some eBay stores, but you do not get real warranty then and what about the service? I recommend geting a T42 - I believe the T43 is inferior to it and the T40s and T41s don't have "LapStore Garantie" anymore. You can get them without operating system and can customize the hard disk, memory and optical drives - unfortunately you cannot downgrade those, which is my only gripe with them.

12 January 2006

Joachim Breitner: Schmiz' Katze im Jubez

Heute war die Impro-Theater-Gruppe der Uni, Schmitz’ Katze, im Jubez zu sehen. Diese leider nicht sehr h ufigen Auftritte lasse ich mir - soweit m glich - nicht entgehen. Trozdem wird es einem dank der Improvisation nicht langweilig. So wurde man heute mit Reagenzglaskindern, Lagefeuergeschichten und Horror-B gelbrettern begl ckt.Nach einer kurzen Aufw rmzeit anfangs zeigte die Truppe vor der Pause Bestleistung. Bew hrt haben sich dabei die traditionellen Spiele. Nach der Pause wurde lange und am St ck “Fishing in the Stream of Conciousness” gespielt, und sollte wohl einen k sterlischen Touch bekommen. Das war schade, denn es zog sich bisweilen ein wenig und wirkliche Lacher waren etwas d nner geseht. Um so beeindruckender war Jens’ Auftritt als posenreicher Jesus beim Abendmal. Auch sonst - als komplettes Italienisches Landhaus mit K hlschrank und BH - war er heute in bester Verfassung. Daher geht mein “Bester Improvisat r des Abends” an Jens.F r die Freunde des Theatersports, der kompetitiven Variante des Improtheaters: Am 10. Dezember kommt die T binger Theatersportgruppe Harlekin ins Jubez: Diese professionelle(?) Truppe spielt in einer andren Liga, hier sind die Sponanlieder chartreif und jede Szene erneut orginell (zumindest habe ich sie so in Erinnerung).