Trying out some Deadly Linux Commands part 1

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There are a selection of Terminal Commands in Linux that we’re told are Deadly to run, but just how lethal are they? In this video I try out a selection of them in VirtualBox with Ubuntu 15.10.

Part 2:

0:20 Fork Bomb
1:47 rm -rf /
2:17 Disguised rm -rf /
2:26 mkfs.ext4 /dev/sda1
3:14 dd if=/dev/random of=/dev/sda
4:04 mv / /dev/null
4:28 rm -f /usr/bin/sudo;rm -f /bin/su



  1. I know why the command sudo mv / /Dev/null didn't work. It is because / is a mounted directory which is only able to be moved to another mounted directory but you were trying to move it to a device file (the black hole for Linux), not a directory, which does not make any sense. However, if mv sees the second argument as a file, it renames the first argument to the name of the second argument. However, because the directory they your have provided is root, it cannot be renamed, so the command didn't work.
    I also know why you were able to install VLC even though you have removed sudo and su. It's because gksudo, which allows one to enter their password through gui, was still available, which does not need sudo or su to work. This had allowed you to give permissions and still install VLC. Hope that helps.

  2. The first command worked properly. Bravo. However, just like all fork bombs, it's only damaging until a reboot – it infinitely calls itself, hogging up
    The second command… Goddamnit. If it says that you need –no-preserve-root to do this, then add the –no-preserve-root parameter, please. This command in bare form was made up before the –no-preserve-root failsafe was added, when it was not needed to add the parameter to successfully rm -rf /.
    The third command chunk is absolutely full of syntax errors and commands that are not bundled with Ubuntu. However, maybe you were supposed to run that in a script rather than copying it into the shell?
    The fourth command – well, pretty self-explanatory, isn't it?
    The fifth command – maybe your system demanded too many random digits and that's why it froze? Also, GPT needs a lot more writing to be overwritten. /dev/random is slow, /dev/zero should've worked.
    The sixth command – you can't move a directory to a non-directory because that's how fucking filesystems work. /dev/null is not a directory, it's a character device with the behavior of "output nothing when read, accept any writes and do nothing with the written data". For example, sending a command's stdout to /dev/null (as in "[command] > /dev/null") means that the command's output is discarded.
    The seventh command – it's more of a "pulled-out screw" command than a "destroy everything" command. It means that programs cannot authenticate for root privileges properly, which is pretty bad, but you can easily fix this with a Live USB or recovery mode. Also, it's possible to fix this without rebooting by logging in to SSH or a TTY as root (remember your root password!) or using pkexec to authenticate.

  3. Managed to ruin my OS when studying linux one day when i was too tired. Like 6 years ago, cant remember if I had ubuntu tho. Can't remember exactly what I did or how, managed to start deleting root directory tho. No biggie tho, think we pretty much reinstalled OSs 3-4 times a week at average, and was smoother then reinstalling bsd or solaris. Crashing systems was seen as a good thing by teachers, nothing better to practice on.

  4. A few years back, I made the mistake of setting up commands on the administration terminal. The next thing I got was a login loop. I had accidentally killed the menu bar and had to use commands to get it back from the admin terminal. Once I finished, I typed reboot. Lesson, use a virtual machine if you are going to experiment.

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