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  1. inapp software

    Installing inapp on Armbian.

    Update everything after the fresh installation to get the latest kernel and packages:

    apt-get update
    apt-get upgrade
    

    Disable the NetworkManager deamon and save ~6MB of RAM:

    root@nanopineo:~# systemctl disable NetworkManager
    Removed symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service.
    Removed symlink /etc/systemd/system/multi-user ...
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  2. inapp OTG ethernet

    Setting-up the USB OTG port as an Ethernet 'gadget' device.

    About "sunxi"

    sunxi is the community working on the open-source environment for Allwinner chips... but it has to be kept in mind, and they write it right on the top of the front page [1], that:

    Allwinner [...] is violating the ...
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  3. inapp qmake install

    make install

    The easy way to install your Qt program with qmake is to add this to your .pro file:

    target.path = /usr/local/myprogram
    INSTALLS += target
    

    qmake will find itself what is the binary to copy to the target path. According to the documentation [1], only target and dlltarget ...

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  4. inapp software (OS) 2

    Now the operating system. Take two with Armbian.

    Step 1: Get the SD-card image

    Get the OS image Armbian_5.25_Nanopineo_Ubuntu_xenial_default_3.4.113.7z at [1].

    Step 2: Write the SD-card image

    Write the image to the SD-card (4GB min):

    sudo dd if=Armbian_5.25_Nanopineo_Ubuntu_xenial_default_3.4.113.img of=/dev/mmcblk0 ...
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  5. inapp software (OS)

    Now the operating system. Take one with the official image from FriendlyArm.

    Step 1: Get the SD-card image

    Get the OS image nanopi-neo-ubuntu-core-qte-sd4g-20170204.img.zip at [1].

    Step 2: Write the SD-card image

    Write the image to the SD-card (4GB min):

    sudo dd if=nanopi-neo-ubuntu-core-qte-sd4g-20170204.img of=/dev/mmcblk0 bs ...
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  6. inapp hardware

    Cute little ARM board (inner active ingredient) + Tiny 3D-printed housing (color plastic hull) + Transparent sticker (attractive branding) = your new medication for pretty printing.

    The Nano Pi NEO

    The Nano Pi Neo is a cheap Chinese ARM board with everything needed (Ethernet, On-the-Go USB) and a tiny 40x40mm form-factor [1].

    The ...

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  7. Qt socket and systemd

    How to create a systemd-friendly QWebSocket server?

    Surprisingly, there does not seem to be any official Qt documentation for this use-case. Enjoy.

    Introduction to systemd socket-based services

    The keyword here is socket-based activation. [1]

    systemd will create the socket first and listen to incoming connections. On first incoming connection, the ...

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  8. About Linux kernel printk timestamps

    What is this timestamp in each kernel printk message?

    Quote from [1].

    Printk-time uses the routine sched_clock() in the kernel. On some platforms, sched_clock() only has a resolution of 1 jiffy (which may be 10 milliseconds or longer). This means that you will only see the time increment at this ...
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  9. Debian build image with virtualbox

    Prepare a Debian virtual image to build packages.

    Step 1: Get Debian install image

    Get the netinstall 248MB image (e.g., debian-8.7.1-amd64-netinst.iso) at this address [1], and start a new virtualbox machine.

    Only need a minimalistic system.

    Ready!

    Step 2: Prepare for package build

    A short introduction ...

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  10. SSH and user account without password

    Highly insecure!

    Step 1: Create user with no password

    Create a user with a password, and delete it later ([1]):

    root@inabox:/home/ina# adduser test
    [...give a password...]
    root@inabox:/home/ina# passwd -d test
    passwd: password expiry information changed.
    

    Step 2: Let the user log in

    In /etc ...

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  11. kprobes to DLT

    Initial example for setting a kernel tracepoint and forward the trace output over DLT (Autosar Diagnostic Log and Trace).

    Howto set a kprobe

    This example is taken straight out of the Linux kernel documentation at [1]. For details about the kprobes internals, see [2].

    # The tracing facility is in the ...
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  12. How Linux kprobes works

    How do Linux kernel probes (kprobes) work

    Everything below comes from reading kprobes.txt at [1].

    Summary

    There are kprobes and jprobes. jprobes are specialized kprobes for function calls, making it easier to get the function parameters. It is usually useful to filter function call traces according to the value ...

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  13. GNU/Linux system performence

    What else is happening again?

    (process:704): GLib-WARNING **: poll(2) failed due to: Invalid argument.
    

    Using sysctl

    $ sysctl net.core.somaxconn
    net.core.somaxconn = 128
    
    $ find /usr/include -name socket.h
    /usr/include/asm-generic/socket.h
    /usr/include/linux/socket.h
    /usr/include/x86_64-linux-gnu/bits/socket.h
    /usr/include/x86_64-linux-gnu ...
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  14. Javascript onChange event and IME

    But wait! What happens when I use Chinese input? ...types CTRL+Space and start composing... Oh shit!~ [1]

    Capturing key strokes is nice, but it does not support virtual keyboard like on tablet or smartphones and more advanced input methods such as Chinese/Japanese or other writing systems.

    The problem ...

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  15. Reading UTF-8 from a pipe

    This works

    std::string l;
    
    // Read lines here
    while(std::getline(std::cin, l))
    {
        // Send Unicode string
        emit newLine(QString::fromStdString(l));
    }
    

    This works because \n (newline) is a single byte in UTF-8.

    This does not work

    char c;
    
    // Read bytes here
    while(std::cin.get(c))
    {
        // Send Unicode single ...
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  16. <KeyCode>-<TerminalCode>-<CharCode>

    A story which begins on the keyboard, goes through a pseudo-terminal, and ends up on the screen.

    Now that you love ptypipe (see previous post), we are ready to pipe everything and finally control gdb:

    $ makefifo input.cli
    $ python ptypipe.py "" "gdb -q" < input.cli | myGreatControlProgram > input.cli
    

    Step 1 ...

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  17. Yes, you want working completion in your gdb

    You can pipe commands to gdb, but how to have auto-complete on those commands?

    Naive attempts

    A initial little try is promising, we can pipe commands to gdb:

    ~$ echo "show endian" | gdb -q
    (gdb) The target endianness is set automatically (currently little endian)
    (gdb) quit
    

    The command show endian was ...

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  18. <CPU>-<vendor>-<OS>

    Questioning about the "target triplet" <CPU>-<vendor>-<OS> used by the GNU build system to describe a target

    When building gdb targeting a different platform, one must choose --host, --build, and --target parameters.

    The target parameter has the following format [1]:

    <CPU>-<vendor>-<OS>
    

    You can get the target of ...

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  19. OpenSearch plugin for inapp

    How to add an OpenSearch to your website

    OpenSearch is a standard way to make a webbrowser know that your page is actually a search engine. Mozilla [1] and Microsoft [2] explain you how to do it, but a quicker tutorial is found there [3].

    My own OpenSearch configuration file ...

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  20. HTML man pages

    Many websites host HTML rendering of man pages. How to make them yourself?

    Stackoverflow always has an answer for those questions [1].

    A tool without many dependencies is mandoc [2], and of course, it has its mandatory HTML man page there [3].

    ./configure
    make
    ./mandoc -Thtml -Ostyle=mandoc.css ../man-pages-4 ...
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  21. Get the documentation of gcc command-line arguments

    gcc has an extensive documentation [1] in the texinfo format (.texi file extention). texinfo [2] can be converted into many different output formats, such as HTML, PDF, ...and generic XML.

    I would like to write a quick-and-dirty script to extract the description of each command-line argument of gcc. I could ...

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