395 lines
17 KiB
HTML
395 lines
17 KiB
HTML
<!DOCTYPE html>
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<!-- vim: set ts=2 sw=2 et tw=120: -->
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<html>
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<head>
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<meta charset="utf-8">
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<title>maggicl - Atelier INF (blog)</title>
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<meta name="author" content="Claudio Maggioni (maggicl@usi.ch)">
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<link href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css"
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rel="stylesheet">
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<link href="https://fonts.googleapis.com/css?family=Fira+Sans&display=swap"
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rel="stylesheet">
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<link href="css/main.css" rel="stylesheet">
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</head>
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<body>
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<header>
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<h1><code>maggicl</code> - Atelier INF</h1>
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</header>
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<div class="content">
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<nav>
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<ul>
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<li><a href="index.html">Home</a></li>
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<li><a href="blog.html">Blog</a></li>
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<li><a href="3d_print_service.html">3D prints</a></li>
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<li><a href="gallery.html">Gallery</a></li>
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</ul>
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</nav>
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<main>
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<article>
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<section class="title">
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<h2>How to rickroll people that try to run "rm -rf" on your system</h2>
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<h4>Jul 28, 2016 -- <a class="author" href="index.html" data-me>Claudio Maggioni</a></h4>
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</section>
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<section>
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<figure class="img">
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<figcaption>My Spotify with a bunch of Rick Astley songs</figcaption>
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<a href="img/blog/spotify_rickastley.png">
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<img src="img/blog/spotify_rickastley.png"
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alt="My Spotify with a bunch of Rick Astley songs">
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</a>
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</figure>
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<p>
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<strong>
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WARNING: The method showed here could not prevent the actual execution of "rm -rf"
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if the "UNIX vandal" is clever enough. Proceed at your own risk, and make backups!
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</strong>
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</p>
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<p>
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I like Rick Astley late 80's songs, and you can see them here in my Spotify:
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</p>
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<p>
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I like rickrolling people too, especially if they are trying to delete my entire
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<code>/home</code> directory or, even worse, <code>/</code>. Since I learned
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how to use the <code>alias</code> built-in, I wanted a way to prevent that
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random people tinkering with my laptop (that I may forgot to lock) could
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delete potentially important stuff, just for fun or boredom.
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</p>
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<p>
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The method that I will show will lock any <code>rm</code> command runned in
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both recursive and force mode, so <code>rm -rf</code>, <code>rm -f -r</code>
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and <code>rm -r --force</code> are all blocked, even if they are runned with
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<code>sudo</code>. I am going to alias the rm command in
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<code>/etc/profile</code>, <code>/etc/bash.bashrc</code> and in
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<code>/etc/zsh/zshrc</code> (I am a zsh user) so that the rickroll will be
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possible from all users, even root and the ones with a brand new
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<code>.bashrc</code> or <code>.zshrc</code>. Here is the code I appended to
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those files:
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</p>
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<figure class="right">
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<figcaption><em>Alias</em> code to use to activate <code>rmAlias</code></figcaption>
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<pre>alias rm=/bin/rmAlias
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alias sudo='sudo '
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# this enables aliases in sudo, see
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# http://askubuntu.com/questions/22037</pre>
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</figure>
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<p>
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Since <code>alias</code> is not able to control the flags of the aliases (see
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<a href="http://apple.stackexchange.com/questions/50963/">here</a>, we are going
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to redirect each call of <code>rm</code> to
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<code>/bin/rmAlias</code>, that would run the command if it is safe. I did
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not use a function because it is a bit tricky to make that work with
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<code>sudo</code>. So, let's see the code I put in <code>rmAlias</code>:
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</p>
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<figure>
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<figcaption>Code for <code>rmAlias</code></figcaption>
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<pre>
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#! /bin/bash
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# Rickroll whoever tries to desert this system, even root.
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# To achieve this, set the appropriate aliases even in
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# /etc/profile and similars.
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# Video played when rickrolling
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ROLLVIDEO=/opt/anti-rm/serious-video.mkv
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# it's just Never Gonna Give You Up on my system, but
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# feel free to customize this!
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rickroll(){
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echo "Never gonna desert this system..."
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xdg-open $ROLLVIDEO 2>&1 &
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exit 0
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}
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while getopts ":rf-" opt; do
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# Prevent '--force' to be detected as -r and -f
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if [ "$opt" = "-" ]; then
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OPTIND=$OPTIND+1
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continue
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fi
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if [ "$opt" = "r" ] || [ "$opt" = "f" ]; then
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if [ "$tmp" = "" ]; then
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tmp=$opt
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continue
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elif [ "$tmp" != "$opt" ]; then
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rickroll
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fi
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fi
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done
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for var in "$@"
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do
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if [[ "$var" = "--force" && "$tmp" = "r" ]]; then
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rickroll
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fi
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done
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# If it's safe, just run rm
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/bin/rm "$@"
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exit $?</pre>
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</figure>
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<p>
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It may look messy to a <em>UNIX</em> guy more experienced than me, but it
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works. The <code>getopts</code> built-in sees if both the <code>-r</code> and
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the <code>-f</code> flags are used and, if so, it starts
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<code>rickroll()</code>, which opens with <code>xdg-open</code> that amazing
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clip from <em>RickAstleyVEVO</em>. From line 30 and below, the script checks
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if the <code>--force</code> flag is used instead of <code>-f</code>.
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</p>
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<p>
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Let's give execution permissions to the script we have just created:
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</p>
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<figure class="right">
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<figcaption>Giving execution permissions of <code>rmAlias</code></figcaption>
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<pre>
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# chmod +x /bin/rmAlias</pre>
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</figure>
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<p>
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Restart your shell, and enjoy. If you want to test safely, I suggest trying
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to run <code>rm -rf</code> with no folders or a nonexistant one, since this
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script stops even these commands.
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</p>
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<p>
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If you want even more security, you can rename this script to
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<code>/bin/rm</code> and move the original one in some other place, getting rid
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of all the aliases. I prefer the solution above because it's tidier: you
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haven't to move anything. In fact, this could be just an AUR package...
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</p>
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</section>
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</article>
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<article>
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<section class="title">
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<h2>Installing Gentoo on a Lenovo ThinkPad X60s</h2>
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<h4>Jul 12, 2016 -- <a class="author" href="index.html" data-me>Claudio Maggioni</a></h4>
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</section>
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<section>
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<figure class="img">
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<figcaption>The <em>X60s</em></figcaption>
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<a href="img/blog/thinkpad1.jpg">
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<img src="img/blog/thinkpad1.jpg" alt="An image of the ThinkPad X60s">
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</a>
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</figure>
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<p>Currently, my only laptop is a
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<a href="http://www.thinkwiki.org/wiki/Category:X60s">IBM/Lenovo ThinkPad
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X60s</a>, a top line <em>ultrabook</em> from 2006 that features:
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</p>
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<ul>
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<li>An Intel Core Duo L2400 dual core 32 bit CPU, clocked at 1.66 Ghz;</li>
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<li>2GB of RAM;</li>
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<li>60GB of SATA1 hard drive;</li>
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<li>Wifi, Bluetooth, trackpoint mouse only, 56k modem, and a decent set of
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I/0 ports (including a CardBus slot!).</li>
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</ul>
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<figure class="right img">
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<figcaption>The <em>X60s</em> one more time</figcaption>
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<a href="img/blog/thinkpad2.jpg">
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<img src="img/blog/thinkpad2.jpg" alt="Another image of the ThinkPad X60s">
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</a>
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</figure>
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<p>
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This machine had an installation on <em>Arch Linux</em>, and I was using it
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for school stuff. It runned smoothly <em>KDE5</em>, <em>Atom</em> (great
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editor, I am using it to write this article), and it was usable even with
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<em>PhpStorm</em>. Pretty impressive for such an old thing, right?
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</p>
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<p>
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Since now I don't need this laptop every day I decided to give a try
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at Gentoo,
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another rolling relase, DIY install distro. This was both a test of my
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skills, my patience and the performances of the machine. For those of you
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that don't know, Gentoo hasn't binary packages: imagine using Arch with just
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a developer mantained AUR.
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</p>
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<p>
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I followed the <a href="https://wiki.gentoo.org/wiki/Handbook:Main_Page">
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installation guide</a> without any problem until I had to <em>emerge</em>
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and install 309 packets from my <code>@world</code> set: it took 15 hours!
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The compilation of <code>cmake</code> crashed because of memory starvation,
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and so I had to use a spare USB stick as swap (the root file system was not
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resizable as it was JFS). After some research and a couple of seconds in
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<code>top</code> I discovered that
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<a href="https://en.wikipedia.org/wiki/Physical_Address_Extension">PAE</a>
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was not implemented in the install disk kernel. <strong>TIP:</strong> if you
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want to use a nicer install enviroment, use the <em>Arch</em> ISO. With
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<em>Gentoo</em>, the initialisation of the file system is made with a
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<a href="https://wiki.gentoo.org/wiki/Stage_tarball#Stage_3"><em>stage 3
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tarball</em></a> and not by tools like
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<a href="https://wiki.archlinux.org/index.php/beginners'_guide#Install_the_base_packages">
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<code>pacstrap</code></a>.
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</p>
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<p>
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I had another problem with <code>make menuconfig</code>, the tool used to
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specify what features add or remove in your compiled from source Linux kernel.
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The <code>ncurses</code> menu showed me 64bit options, even if the install
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disk and the CPU were both 32 bit. If you have this issue too, you can set
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the <code>ARCH</code> variable by your own:
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</p>
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<figure>
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<figcaption>Compiling the kernel</figcaption>
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<pre># make ARCH=i386 menuconfig
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# make ARCH=i386
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# make ARCH=i386 install</pre>
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</figure>
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<p>
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At the end, I made it! I only have a base install, but i can show you
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<code>screenfetch</code>:
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</p>
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<figure class="img">
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<figcaption>The laptop running <em>screenfetch</em></figcaption>
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<a href="img/blog/screenfetch.jpg">
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<img src="img/blog/screenfetch.jpg" alt="The laptop running 'screenfetch'">
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</a>
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</figure>
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<p>
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I have not installed <em>Gentoo</em> in dual boot because I did not figure
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out how to switch my bluetooth dongle in HID mode yet, so I can't select
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the OS with <code>rEFInd</code>. Hope this rambling was, if not useful,
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at least entertaining!
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</p>
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</section>
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</article>
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<article>
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<section class="title">
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<h2>Get a Bluetooth keyboard work with Arch Linux</h2>
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<h4>Jul 7, 2016 -- <a class="author" href="index.html" data-me>Claudio Maggioni</a></h4>
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</section>
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<section>
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<figure class="img">
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<figcaption>The keyboard in question</figcaption>
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<a href="img/blog/rapoo.jpg">
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<img src="img/blog/rapoo.jpg" alt="The keyboard in question">
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</a>
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</figure>
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<p>
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I've recently got a Rapoo E6100. This is a minimal and space saving Bluetooth
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3.0 keyboard. If you pair it with Windows 10, it will remain paired after
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reboot, giving the possibility to use it since the login screen. After
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installing the Bluetooth stack on my Arch via the <code>bluez</code> and
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<code>bluez-utils</code> packages I thought the pairing process would be as
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simple as Windows if I used the KDE GUI menus for Bluetooth management. That's
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not true. The keyboard, once paired, will reconnect automatically just after
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<code>plasmashell</code> loaded, leaving me without keyboard during the SDDM
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login screen and, of course, during a non-graphical session.
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</p>
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<p>
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As usual, i've searched help in the ArchWiki, founding
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<a href="https://wiki.archlinux.org/index.php/Bluetooth_keyboard">this</a>
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article. With that, i've succesfully reconnected my Bluetooth keyboard using
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the <code>bluetoothctl</code> utility. The next step was configuring the
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service for auto connection during boot. I've created the
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<code>btkbd.conf</code> and the <code>btkbd.service</code> files, enabling
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the last one with systemd. Let's give a look to the service file:
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</p>
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<figure class="right">
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<figcaption>The <code>btkbd.service</code> file</figcaption>
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<pre>[Unit]
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Description=systemd Unit to automatically start a \
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Bluetooth keyboard
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Documentation=archwiki: Bluetooth_Keyboard
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Requires=dbus-org.bluez.service
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After=dbus-org.bluez.service
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ConditionPathExists=/etc/btkbd.conf
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ConditionPathExists=/usr/bin/hcitool
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ConditionPathExists=/usr/bin/hciconfig
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[Service]
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Type=oneshot
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EnvironmentFile=/etc/btkbd.conf
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ExecStart=/usr/bin/hciconfig ${HCIDEVICE} up
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# ignore errors on connect, spurious problems with bt?
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# so start next command with -
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ExecStart=-/usr/bin/hcitool cc ${BTKBDMAC}
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[Install]
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WantedBy=multi-user.target</pre>
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</figure>
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<p>
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Line 13 enables the Bluetooth dongle, and line 16 connects it to the keyboard we gave the mac address in <code>/etc/btkbd.conf</code>. This should work flawlessly, right? Of course it doesn't. The service starts before the <code>dbus-org.bluez.service</code> is loaded and fails. However, if the service is started manually after login the Bluetooth keyboard works. After hours of trying figuring out what was wrong I've almost asked for a return on Amazon! The last attempt I made was with sddm disabled and involved built from scratch service:
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</p>
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<figure class="right">
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<figcaption>My service file</figcaption>
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<pre>[Unit]
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Description=auto connect a Bluetooth keyboard
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[Service]
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Type=oneshot
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ExecStart=/bin/hciconfig hci0 up
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ExecStart=/bin/hcitool cc 00:11:22:33:44:55
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[Install]
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WantedBy=bluetooth.target</pre>
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</figure>
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<p>
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This incredibly worked. I think the problem was that <code>multi-user.target</code> that needs to be reached earlier than <code>bluetooth.target</code>. I got rid of all the tidiness of the ArchWiki solution just to be sure that was not the problem, but I think you can use all of that just correcting <code>WantedBy=</code>. Currently I haven't an ArchWiki account nor a forum one, but as soon as I'll register I'll correct the article.
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</p>
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<p>
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Last thing: I discovered that my Bluetooth dongle is CSR 8510 A10 based so expect some ramblings about <a href="http://www.0xf8.org/2014/02/the-crux-of-finding-a-hid-proxy-capable-usb-bluetooth-adapter/">hid proxy</a>.
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</p>
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</section>
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</article>
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</main>
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<aside>
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<ul>
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<li><a href="https://reddit.com/u/Praticamentetilde">
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<i class="fa fa-reddit" aria-hidden="true"></i> Praticamentetilde
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</a></li>
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</ul>
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</aside>
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</div>
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<footer xmlns:dct="http://purl.org/dc/terms/"
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xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#">
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<a rel="license"
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href="http://creativecommons.org/publicdomain/zero/1.0/">
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<img width="88" height="31"
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src="http://i.creativecommons.org/p/zero/1.0/88x31.png"
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alt="CC0" />
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</a>
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<section>
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<p>To the extent possible under law,
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<span resource="[_:publisher]" rel="dct:publisher">
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<span property="dct:title">Claudio Maggioni</span></span>
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has waived all copyright and related or neighboring rights to
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<span property="dct:title">SA3 AS1 Website</span>.
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This work is published from:
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<span property="vcard:Country" datatype="dct:ISO3166"
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content="CH" about="[_:publisher]">
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Switzerland</span>.
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</p>
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<p>Page last updated on 2019-09-22</p>
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</section>
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</footer>
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</body>
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</html>
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