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Linux Appliance Design 53

Posted by samzenpus
from the do-it-yourself dept.
s1axter writes "A week and a half ago I received Linux Appliance Design by Bob Smith, John Hardin, Graham Phillips and Bill Pierce, published by No Starch Press. This is one of No Starch's latest titles and was released in the beginning of April. As a hardware/embedded systems guy I was really eager to get my hands on the book. For those who don't know what the book is about, it's about making an application specific utility, an electronic tool or "appliance" that can be used for a specific task. The book defines an appliance as "A device designed to primarily perform a single function" and that's exactly what they do." Read on for the rest of S1axter's review.
Linux Appliance Design
author Bob Smith, John Hardin, Graham Phillips and Bill Pierce
pages 344
publisher No Starch Press
rating 9
reviewer s1axter
ISBN 1-59327-140-9
summary A text on developing an application specific device, very informative


The book revolves around Laddie, an example alarm system for a building. The book includes a complete explanation of the system, what design features it uses, and a LiveCD with the final application for your hacking pleasure.

I have to say, Linux Appliance Design is well written and very, very thorough. This is not a beginner text, the authors focus on Linux programmers who understand C and Linux systems and want to take it a step further than conventional software. If you think this is a book for you, you should be a C/Linux guru, or dust off those old textbooks and brush up on your stuff before you pick it up.

When a friend asked me what was in the book I gave him the response, "Everything you need to make a sweet daemon with any interface you want". This is exactly what Linux Appliance Design is, a library in a book. Nostarch.com has a chapter list for the text, so you can see what I mean.

The layout for the text is well organized and starts where every project should, architecture and design. Personally I felt the authors were beating the dead horse after a couple of pages when everything kept coming back to separating interface from implementation, but hey, it's an important point that a lot of people seem to miss.

An interesting chapter is the explanation of the Run-time-access library the authors developed. Modeled from PostgreSQL, the RTA lib is an impressive solution that allows for daemon communication and configuration from any language that can talk to a database. This library is released under the GPL and can be downloaded from the companion site of the book The RTA is also used for the rest of the book, so don't skip it or you'll have no idea what they are talking about.

The text is not only an explanation of the Laddie system using the RTA, it is an all encompassing design text, which I really like. There are chapters dedicated to building different frontend UIs for the system and communication protocol discussion. This is what transforms the text from book into library. Each chapter can almost stand on its own as an application of that language or program. I was quite impressed with the web interface chapter and how the authors compared web servers and designed a system, and also with the framebuffer chapter on how to make a cool graphical interface.

A common theme for all the chapters is the structure. The authors discuss and design each element they use in the system before looking at one program or daemon. For anyone who has written or read development reports the format is very similar; explain what you designed, why you chose those components, why you passed on others, how the systems works and finally what you would do different next time. This format kind of reminded me lab reports in school, cover all question you think your professor audience might ask.

Overall Linux Appliance Design is a well written, detailed and thorough book with a lot of information. I would recommend this title mainly to someone who is interested in daemon development or server design however it can be read by anyone who wants to see a full project develop cycle.

s1axter is the main poster for Geeksinside.com. Geeksinside.com is a DIY, hardware hacking, technology blog that showcases links, reviews and project


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Linux Appliance Design

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  • by Anonymous Coward on Monday April 30, 2007 @03:19PM (#18931617)
    I'll enjoy it along with beers from my linux powered refrigerator, making sure to switch off my linux powered cell and watching my wife enjoy herself with her linux powered vibrator.

    Tux gets everywhere.
  • Nifty book (Score:3, Interesting)

    by jshriverWVU (810740) on Monday April 30, 2007 @03:23PM (#18931667)
    One thing I'd like to build is a lirc device that also acts as a power switch. So you can use a remote control to also turn the computer on. This could be useful for things such as a Myth box.
    • Re: (Score:3, Funny)

      by CastrTroy (595695)
      Aren't you supposed to leave your Myth box on, so that it can record your shows?
      • by PCM2 (4486)
        My Windows Media Center box comes with a remote control that can be used to turn the computer off and on. It communicates with a USB receiver that has the ability to bring the computer out of sleep (including S3). Apparently it's that USB receiver that handles scheduled wake-up/sleep, as well. So when I'm done using the computer as a PC, I hit the sleep button and walk away. It will wake itself up to record my shows and then go back to sleep.

        I'm still waiting for Ubuntu to sleep reliably on my laptop. It se
        • by itwerx (165526)
          box comes with a remote control that can be used to turn the computer off and on. It communicates with a USB receiver

          A lot of motherboards have a BIOS option to wake from sleep on USB activity. It's not a true power on/off but pretty close.
                (Now if MythTV could just use the other BIOS settings for scheduled power on that would be pretty cool!)
          • by CastrTroy (595695)
            It's not that hard from what i've heard. I think it requires echoing something to a file in proc, which will set the next wake up time. I've been looking for something similar for my sagetv windows box. Have it turn itself off when there's nothing to record for the rest of the night and set the bios to turn itself on 5 minutes before the next show comes on.
    • by Ricochet (16874)
      Maybe what you need is my book (boy am I going to catch sh*t for this): Linux Smart Homes For Dummies [linuxha.com]
    • the problem with many small devices is power... I read an article about "energy harvesting", so that you don't need power cords or batteries to make remote controls for things... this would be really cool for home automation!

      energy for free [cieonline.co.uk]

    • by Aluvus (691449)
      Use a relay connected to the motherboard "power switch" header of the target system. A momentary "high" voltage is all you would need. Or if you want to (rudely) shut down all other connected devices, use a relay to shut down the power strip everything is connected to.
    • Actually a solution I've seen is using a PIC micro controller to translate the signals from the IR receiver send signals through to LIRC via serial or USB but when a power signal comes through switch the computer on via the Wake on Lan header on the motherboard
  • by EmbeddedJanitor (597831) on Monday April 30, 2007 @03:31PM (#18931797)
    The RTA approach is potentially useful for some very low volume data flows (system monitoring etc), but it is not the way you'd design any performance critical stuff (which many true embedded systems need). Most Linux embedded systems are portable devices that run on batteries, so efficiency is important. Efficient execution translates to longer battery life.

    Many embedded systems need very high levels of responsiveness (sub-millisecond) which RTA is unlikely to provide. I've worked on Linux embedded systems that could reliably crank events within 50 microseconds, but that required the use of custom drivers.This responsiveness is why RTOSs and "no OS" solutions will dominate embedded space for a long time yet.

    • Re: (Score:3, Informative)

      by greg1104 (461138)
      After reading their related RTA description [linuxappli...esign.com.], your comments don't make any sense to me. It's an API for exposing stats or other information you collect in your program via a standardized sockets protocol. If no one is actually reading the stats, there is no overhead beyond whatever you already have in your app to collect them. Yes, the app may slow appreciably when someone is connected and reading the data via this interface; as long as responding to that is in a low-priority process, who cares?
    • I agree. A lot of these devices could be built using an 8051 and much less than 64K of program memory and still be much more appropriate for real-time applications. "Desktop" OS's are great for general purpose use, but overkill for most embedded applications.
  • Toasting bread with your Linux toaster.. for Dummies

    Configuring For Toasting:

    Change directory to /usr/src/Linux and issue the command:
    make menuconfig
    This will build a few programs and then quickly pop up a window. The window menu lets you alter many aspects of toast configuration.
    After you have made any necessary changes, save the configuration and follow these instructions--do a

    make dep; make clean...

    ..... snip few pages later ....

    and then, if you are on a toaster slower than 200MHz, go and make a cup of
    • by $RANDOMLUSER (804576) on Monday April 30, 2007 @04:08PM (#18932347)
      Making toast the *NIX way:

      1. Prepare the soil.
      2. Plant the wheat.
      3. Weed, fertilize, water.
      4. Harvest.
      5. Build a flour mill.
      6. Grind wheat into flour.
      7. Cultivate some wild yeast.
      8. Build a brick oven.
      9. Mix flour, yeast and water.
      10. Bake dough to make bread.
      11. Make a knife.
      12. Slice bread.
      13. Insert bread into *NIX toaster.
      • by Burz (138833)
        Step 13 should be broken down into about 7 or 8 (or 28) sub-steps that involve:

        * Not finding the desired bread in the bread-package manager.

        * Downloading source off author's site

        * Realizing it doesn't have the neccessary feature that you heard people talking about, so you need to get the CVS version instead (install CVS and learn it post-haste).

        * Chasing down all the supporting library dev packages to get it all to compile.

        * Watch as the install process fails to change pertinent system settings (no desktop/
      • by sminkin (1002497)
        14. Profit!
  • by anubi (640541) on Monday April 30, 2007 @05:45PM (#18933637) Journal
    all this fuss over a fullblown OS to do simple tasks?

    This paradigm was overwhelming to me when I was in corporate... this obsession of making simple things, like tying shoelaces, into a federal affair.

    For years, I have used simple microcontrollers, like the PIC or AVR to do this stuff. For microwatts. Highly reliable, and I *know* exactly what I told that microcontroller to do. Simple things, like keep the soda pop cold and nag me if I need to service the vending machine. Tell me whats wrong. That sort of thing.

    It puzzles me to see major corps use way, way, way overpowered/overpriced solutions to the simplest stuff.

    These days, it only takes a microcontroller to do simple stuff, and yes, given a simple TCPIP stack, it commmunicates with the web, pooh, its not that much more than a UART for serial, no??? Especially given one can use IM type protocols for simple quick messages? Sending email is just a little step up.

    I shake my head in pity when I see people trying to use sledgehammers to swat flies.

    Is this just me, or does every other thinking person on Slashdot see it too?

    • Re: (Score:3, Interesting)

      Amen to that.
      For my final year project at university, we were three groups working on robots to map obstacles in a room. The other teams went all out with FPGA boards and fancy high-tech hardware and bluetooth communications. One team had spent in excess of 1500$ on their hardware.

      My team went with a swarm robotics approach, and we built several cheap drones. They were powered by ATMega8's, using cheap RF modules. Total cost? Less than 400$ total for four drones. Now, guess which team had something moving a
    • Why go to the trouble of maintaining your own TCP/IP stack, among lots of other stuff, when you can just throw Linux and an ARM or somesuch board together and go.
      • Re: (Score:2, Interesting)

        by anubi (640541)
        If I am making ONE of 'em, I really don't care how inefficient I may be, as long as the job gets done.

        But, if I am gonna replicate millions of 'em, I try like the dickens to make a clean design, especially minimizing product cost and dependence on anything proprietary that may cease to be supported over the design life of my product.

        Figure 50 years for a sodapop dispenser. Think I'm kidding? I can show you sodapop dispensers made in the 50's STILL IN SERVICE.

        I can also show you trash bins of perfectly g

        • The vast majority of applications do not, and even most embedded systems don't. Also, IM protocols aren't really ideal for that sort of thing. Aside from being poorly standardized, they don't really offer anything that plain old smtp doesn't, and smtp can handle connection loss much better. If something requires immediate attention, SMS is better, in case you're not at your desk.

          I'm not sure what exactly you plan to do with the knowledge that your coke machine is being molested.
          • by anubi (640541)
            Thanks.

            I just try to keep it simple. Very, very simple.

            Every time I have tried to do anything I did not understand thoroughly, it has always come back to bite me.

    • by tbuskey (135499)
      I've read the book myself, mostly. It has applications beyond an embedded design.

      It could be a tiny file server or a network device. I'd love to have some of the interfaces into my thermostat! As time goes on, more and more devices will offer interfaces to get data/control out to computers. This book provides a good example of what and how to offer it. It can certainly be extrapolated to non linux systems.
    • by bensch128 (563853)
      It puzzles me to see major corps use way, way, way overpowered/overpriced solutions to the simplest stuff.

      It's alot more scalable to use a modestly powerful chip and linux then to code everything by hand on a pic controller. In the future, you'll want to add more features. You want process separation so if one process crashes, it won't take down the whole machine, you'll want to add a GUI, you'll want networking, etc etc etc.

      From a cost POV, small arm CPUs make more sense then PICs because they are not much
  • Back when I was at No Starch Press [nostarch.com] (an O'Reilly partner), I remember working with Bob Smith, et al. on this book, and it makes me happy to see that it's seen the light of day.

    This marks the 2nd time in a couple weeks that a No Starch book has been featured here. I hope to see a bunch more.

    -JM

    • I know Bob Smith and John Hardin. I have worked with them both. I know they poured heart and soul into this work. Not for economic gain but for sharing what they know with others. That is the mark of very special people. :-)

"In order to make an apple pie from scratch, you must first create the universe." -- Carl Sagan, Cosmos

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