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<h2 class="post-title" itemprop="name headline">How to rickroll people that try to run "rm -rf" on your system</h2>
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<h4 class="post-meta"><time datetime="2016-07-28T16:00:00+02:00" itemprop="datePublished">Jul 28, 2016</time></h4>
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</header>
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<div class="post-content" itemprop="articleBody">
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<strong>
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WARNING: The method showed here could not prevent the actual execution of "rm -rf" 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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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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<img
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src="/images/spotify_rickastley.png"
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alt="My Spotify with a bunch of Rick Astley songs">
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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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<p>
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<figure class="highlight"><pre><code class="language-bash" data-lang="bash"><span class="nb">alias rm</span><span class="o">=</span>/bin/rmAlias
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<span class="nb">alias sudo</span><span class="o">=</span><span class="s1">'sudo '</span> <span class="c"># this enables aliases in sudo, see http://askubuntu.com/questions/22037/aliases-not-available-when-using-sudo</span></code></pre></figure>
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</p>
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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/how-do-i-add-a-flag-to-an-alias">here</a>, we are going 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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<p>
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<figure class="highlight"><pre><code class="language-bash" data-lang="bash"><span class="c">#! /bin/bash</span>
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<span class="c"># Rickroll whoever tries to desert this system, even root.</span>
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<span class="c"># To achieve this, set the appropriate aliases even in /etc/profile and similars.</span>
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<span class="c"># Video played when rickrolling</span>
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<span class="nv">ROLLVIDEO</span><span class="o">=</span>/opt/anti-rm/serious-video.mkv <span class="c"># it's just Never Gonna Give You Up on my system, but be free to customize this!</span>
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rickroll<span class="o">(){</span>
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<span class="nb">echo</span> <span class="s2">"Never gonna desert this system..."</span>
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xdg-open <span class="nv">$ROLLVIDEO</span> 2>&1 &
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<span class="nb">exit </span>0
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<span class="o">}</span>
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<span class="k">while </span><span class="nb">getopts</span> <span class="s2">":rf-"</span> opt<span class="p">;</span> <span class="k">do</span>
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<span class="c"># Prevent '--force' to be detected as -r and -f</span>
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<span class="k">if</span> <span class="o">[</span> <span class="s2">"</span><span class="nv">$opt</span><span class="s2">"</span> <span class="o">=</span> <span class="s2">"-"</span> <span class="o">]</span><span class="p">;</span> <span class="k">then
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</span><span class="nv">OPTIND</span><span class="o">=</span><span class="nv">$OPTIND</span>+1
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<span class="k">continue
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fi
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if</span> <span class="o">[</span> <span class="s2">"</span><span class="nv">$opt</span><span class="s2">"</span> <span class="o">=</span> <span class="s2">"r"</span> <span class="o">]</span> <span class="o">||</span> <span class="o">[</span> <span class="s2">"</span><span class="nv">$opt</span><span class="s2">"</span> <span class="o">=</span> <span class="s2">"f"</span> <span class="o">]</span><span class="p">;</span> <span class="k">then
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if</span> <span class="o">[</span> <span class="s2">"</span><span class="nv">$tmp</span><span class="s2">"</span> <span class="o">=</span> <span class="s2">""</span> <span class="o">]</span><span class="p">;</span> <span class="k">then
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</span><span class="nv">tmp</span><span class="o">=</span><span class="nv">$opt</span>
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<span class="k">continue
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elif</span> <span class="o">[</span> <span class="s2">"</span><span class="nv">$tmp</span><span class="s2">"</span> <span class="o">!=</span> <span class="s2">"</span><span class="nv">$opt</span><span class="s2">"</span> <span class="o">]</span><span class="p">;</span> <span class="k">then
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</span>rickroll
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<span class="k">fi
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fi
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done
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for </span>var <span class="k">in</span> <span class="s2">"</span><span class="nv">$@</span><span class="s2">"</span>
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<span class="k">do
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if</span> <span class="o">[[</span> <span class="s2">"</span><span class="nv">$var</span><span class="s2">"</span> <span class="o">=</span> <span class="s2">"--force"</span> <span class="o">&&</span> <span class="s2">"</span><span class="nv">$tmp</span><span class="s2">"</span> <span class="o">=</span> <span class="s2">"r"</span> <span class="o">]]</span><span class="p">;</span> <span class="k">then
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</span>rickroll
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<span class="k">fi
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done</span>
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<span class="c"># If it's safe, just run rm</span>
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/bin/rm <span class="s2">"</span><span class="nv">$@</span><span class="s2">"</span>
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<span class="nb">exit</span> <span class="nv">$?</span></code></pre></figure>
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</p>
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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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<p>
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<figure class="highlight"><pre><code class="language-bash" data-lang="bash"><span class="c"># chmod +x /bin/rmAlias</span></code></pre></figure>
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</p>
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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 of all the aliases. I prefer the solution above because it's tidier: you haven't to move anything. In fact, this could be just an AUR package...
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</p>
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Claudio Maggioni
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