19

I freshly installed Ubuntu on my computer a few days ago to run an exclusive program. I finished with it, and I was about to format the drive to reinstall Windows. However, my little brother wanted to run this command in the terminal on it which would destroy the OS, and I thought that it would not hurt since I would be formatting the drive anyway.

It was this: 

sudo rm -rf --no-preserve-root /

Excuse my noobiness if this command is supposed to end the world or something. So it screwed up the OS and I rebooted the PC with the Windows setup USB, planning to format the drive in Windows Setup.

However, upon restart, the monitor was not receiving any input at all. Also, the HDD indicator (or whatever the red light was) wasn't doing one thing. (It was off, in fact.) The fans were working and the DVD drive was, though. (I don't think that there is a PC speaker in there, so if you need some beep error codes, sorry.)

I tried switching the VGA cable from the graphics card to the motherboard, but I still got no input. I tried inserting this old Windows XP disk into the disk drive, but nothing showed up. Mashed the Delete, F12, etc. buttons, but nothing happened. I then looked online and tried a suggestion to reseat the RAM, but nothing changed. I'm thinking of resetting the CMOS manually but haven't gotten to it yet. (Please tell me if you were going to recommend doing so, because I don't want to screw up the PC if I don't have to.)

I have UEFI so I may be able to use a backup chip in case the BIOS is corrupted.

karel
  • 114,770
You
  • 191
  • 7
    There is no way that deleting files would destroy a drive. The command is the same as entering del -s c:\*.* in Windows command line (if my DOS syntax memory is correct). Of course deleting the OS will cause the OS to fail, but nothing more. You should actually get a GRUB prompt. You have some other problem, and it has nothing to do with Ubuntu. Even if the disk failed, that wouldn't affect the USB or DVD boot. – Marty Fried Sep 07 '14 at 22:03
  • 1
    Possible duplicate of How to remove Ubuntu and put Windows back on? – this is what you ultimately want to do, right? Other than that your issue is off topic here since it's not related to Ubuntu which your brother pretty much removed with that command. – David Foerster May 04 '16 at 01:11

5 Answers5

24

This is possible on a UEFI system running systemd.

To summarize, quoting a comment from that bug report:

Point 1:
Deleting /sys/firmware/efi/efivars/ should thrash your EFI configuration, but in a properly implemented EFI this should be recoverable.

Point 2:
There is some pieces hardware out there with broken/poorly implemented EFI, which will can be permanently bricked by doing standard conform stuff to them. See for example the case where Ubuntu bricked some Samsung laptops by storing additional data in some EFI memory. This behaviour was fine by standard but broke this particular implementation.

Point 3:
Running anything as root that writes to /dev/sda will destroy your partition table and/or filesystems. That's bad especially if you have no backup, but after partitioning, creating new filesystems and reinstalling your OS your machine will work again. So you can recover from it by booting some other media and redo your installation.

Point 4:
Thrashing your EFI is a whole different kind of problem. In the worst case you won't be able to do anything with the machine as it will not get to POST. No booting from an other media, no entering some EFI utility to fix missing stuff. A that point your computer is a really expensive paperweight.

The problem occurs in distributions that run systemd and mount efivarfs writeable (at /sys/firmware/efi/efivars). Systemd needs to write there, so distributions using systemd are affected. However, there seems to be no indication that Upstart systems are affected.

muru
  • 197,895
  • 55
  • 485
  • 740
12

Running the command rm -rf / can brick any UEFI device (including the one I am typing from). Doing this deletes all the files which includes mounted drives and EFI firmware variables (this is what bricks). Linux mounts the EFI variables in /sys/firmware/efi/efivars/, and rm -rf / will delete all the files (EFI variables) in that folder. Your computer is most likely a brick and cannot be fixed (EFI uses NVRAM).

Old BIOS computers do not brick for rm -rf /, because they do not have EFI firmware variables which could be deleted. Also, it is possible to do the same thing (delete all EFI variables) on Windows with a few lines of code.

Suici Doga
  • 417
2

There is no way that deleting files would destroy the drive, normally (see my edit at end - apparently, there is a way). The command is the same as entering del -s c:*.* in Windows command line (if my DOS syntax memory is correct). Of course deleting the OS will cause the OS to fail, but nothing more.

If you delete the boot directory along with anything else, even the entire partition, you should still actually get a GRUB prompt. The GRUB bootloader would not get erased because it's not a part of the directory structure, but its menu is, so it should still try to load and give an error.

You have some other problem, and it has nothing to do with Ubuntu. Even if the disk failed, that wouldn't affect the USB or DVD boot process.

EDIT: OK, I think my answer is outdated due to UEFI BIOS, which is something i know little about. Apparently, it is possible to delete critical UEFI configuration information. I believe what happens is that this gets mounted onto the filesystem, and if done incorrectly, will not be read only, and can be erased, thereby erasing it from the BIOS.

Marty Fried
  • 18,466
  • Some disk failures can hang up the POST. Had a disk with a thick oxide coating, which if left off over a weekend, would freeze, and that really stopped everything, until I rapped the disk with a pencil eraser, which freed it up. (vendor replaced the disk). – ubfan1 Sep 08 '14 at 02:37
  • 1
    I've had many disks go bad over my 20+ years of computers, and have never had one affect POST. Until the computer finishes the POST, it doesn't even access the disk. Perhaps if there were a short circuit on a connector, but that's not caused by anything to do with software. – Marty Fried Sep 08 '14 at 03:26
  • I've tried disconnecting the HDD, but still nothing. I feel SO stupid. – You Sep 08 '14 at 10:15
  • Could it just be a BIOS failure? This happened right after the OS got destroyed, after a reboot, so either it's a coincidence or it's that command. – You Sep 08 '14 at 10:17
  • Please look at this answer: http://askubuntu.com/a/767286/518562 – You'reAGitForNotUsingGit Nov 05 '16 at 12:30
  • @AndroidDev: Apparently, I was incorrect, and it is possible. At the time, I didn't know that the UEFI configuration data could be mounted and then erased. I was thinking in terms of traditional BIOS. UEFI is something I tried to ignore, as I don't use Windows at all and had no experience with it at all. Now that I have, I wish I didn't. :-) – Marty Fried Nov 06 '16 at 04:26
  • 1
    No worries! To be totally honest, I would've written the exact same answer if I hadn't seen the one I linked you to. I've always hated UEFI, but now I hate it 10x more... – You'reAGitForNotUsingGit Nov 07 '16 at 12:15
  • @AndroidDev: I'm using it on my main desktop, but have been tempted to stop. But I like to try new things, so I'm still using it. I felt the same way about Grub 2 when it first came out, but used it anyway. – Marty Fried Nov 08 '16 at 05:15
1

I've had the experience that a Windows Installer media may just hang if your HD is using a format Windows doesn't know about (like ext4).

In this case, you should run a Linux LiveCD with GParted (like this one), and format your hard drive to something like NTFS or FAT32 before trying to install Windows.

admirabilis
  • 1,198
  • 2
    His machine won't POST.. – headkase Sep 07 '14 at 22:33
  • 1
    @Bill Although he mentioned about the BIOS, he said his computer became unresponsive with the "Windows setup USB" and the "Windows XP disc", so this could still be the problem. – admirabilis Sep 07 '14 at 22:38
  • 1
    His monitor has no signal, no HDD indicator, no BIOS screen. It's not even POSTing: http://en.wikipedia.org/wiki/Power-on_self-test – headkase Sep 07 '14 at 22:55
0

The major issue here is that a filesystem can span devices. This includes anything mounted. It is a problem for UEFI. Heck, it is a problem for Android. And if you had a mounted camera, say, you have also deleted your DCIM contents, right? So, what did you learn? The manufacturer may be able to help you, and you may be able to flash by other means.

Wipe disks with dd if=/dev/zero next time, and deleting things frivolously will come back to bite you one day. It will all end in tears. You can actually do time for pranking someone like this, it is a little bit worse than del . in the root directory MS-DOS PC.

mckenzm
  • 355
  • 2
  • 11