---
layout: post
title:  "How to rickroll people that try to run \"rm -rf\" on your system"
date:   2016-07-28 16:00:00 +0200
categories: linux
---
<strong>
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!
</strong>

I like Rick Astley late 80's songs, and you can see them here in my Spotify:

![dQw4w9WgXcQ](https://dl.dropboxusercontent.com/s/t9vywa4yjotxv0o/Screenshot_20160728_154506.png?dl=0)

I like rickrolling people myself too, especially if they're trying to delete my entire `/home` directory or, even worse, `/`. Since I learned how to use the `alias` built-in, I wanted a way to prevent that random people tinkering with my laptop (that I may forgot to lock) could delete potentially important stuff, just for fun or boredom.

The method that I'll show will lock any `rm` command runned in both recursive and force mode, so `rm -rf`, `rm -f -r` and `rm -r --force` are all blocked, even if they are launched by `sudo`. I'm going to alias the rm command in `/etc/profile` `/etc/bash.bashrc` and in `/etc/zsh/zshrc` (I'm a zsh user) so that the rickroll will be possible from all users, even root and the ones with a brand new `bashrc` or `zshrc`. Here is the code I appended to those files:

{% highlight bash %}
alias rm=/bin/rmAlias
alias sudo='sudo ' # this enables aliases in sudo, see http://askubuntu.com/questions/22037/aliases-not-available-when-using-sudo
{% endhighlight %}

Since `alias` is not able to control the flags of the aliases (see [here](http://apple.stackexchange.com/questions/50963/how-do-i-add-a-flag-to-an-alias)), we're going to redirect each call of `rm` to `/bin/rmAlias`, that would run the command if it's safe. I didn't use a function because it's a bit tricky to make that work with `sudo`. So, let's see the code I put in `rmAlias`:

{% highlight bash %}
#! /bin/bash
# Rickroll whoever tries to desert this system, even root.
# To achieve this, set the appropriate aliases even in /etc/profile and similars.

# Video played when rickrolling
ROLLVIDEO=/opt/anti-rm/serious-video.mkv # it's just Never Gonna Give You Up on my system, but be free to customize this!

rickroll(){
  echo "Never gonna desert this system..."
  xdg-open $ROLLVIDEO 2>&1 &
  exit 0
}

while getopts ":rf-" opt; do
  # Prevent '--force' to be detected as -r and -f
  if [ "$opt" = "-" ]; then
    OPTIND=$OPTIND+1
    continue
  fi
  if [ "$opt" = "r" ] || [ "$opt" = "f" ]; then
    if [ "$tmp" = "" ]; then
      tmp=$opt
      continue
    elif [ "$tmp" != "$opt" ]; then
      rickroll
    fi
  fi
done

for var in "$@"
do
  if [[ "$var" = "--force" && "$tmp" = "r" ]]; then
    rickroll
  fi
done

# If it's safe, just run rm
/bin/rm "$@"
exit $?
{% endhighlight %}

It may look messy to a UNIX guy more experienced than me, but it works. The `getopts` built-in sees if both the `-r` and the `-f` flags are used and, if so, it starts `rickroll()`, which opens with `xdg-open` that amazing clip from RickAstleyVEVO. From line 30 and below, the script checks if the `--force` flag is used instead of `-f`.

Give execute permissions to the script we've just created:

{% highlight bash %}
# chmod +x /bin/rmAlias
{% endhighlight %}

Restart your shell, and enjoy. If you want to test safely, I suggest trying to run `rm -rf` with no folders or one nonexistant, since this script stop even these commands.

If you want even more security, you can rename this script to `/bin/rm` 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...