## How to rickroll people that try to run "rm -rf" on your system

#### Jul 28, 2016

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!

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

I like rickrolling people too, especially if they are 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 will 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 runned with `sudo`. I am going to alias the rm command in `/etc/profile`, `/etc/bash.bashrc` and in `/etc/zsh/zshrc` (I am 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:

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

Since `alias` is not able to control the flags of the aliases (see here, we are going to redirect each call of `rm` to `/bin/rmAlias`, that would run the command if it is safe. I did not use a function because it is a bit tricky to make that work with `sudo`. So, let's see the code I put in `rmAlias`:

    #! /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 $?

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`.

Let's give execution permissions to the script we have just created:

    # chmod +x /bin/rmAlias

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