5 ms·

I've always preferred this tougher command to screw VMs I was going to delete. dd if=/dev/random of=/dev/sda Depending on how long does it run, you end up

I've always preferred this tougher command to screw VMs I was going to delete. dd if=/dev/random of=/dev/sda Depending on how long does it run, you end up with a more or less screwed computer. It's funny to see how does the machine fall over when you invoke a simple 'cd' command after this.

srl 14y ago
Back when `/dev/mem` was a thing in default kernels (now you need a special config, or a module), I enjoyed `cat /dev/urandom > /dev/mem`. That would usually bork things pretty quickly, so then I would set random offsets with `dd`. Fun times.
- mikeash 14y ago
  See also kmem Russian Roulette: https://twitter.com/shadowcat_mst/status/754107237269504 https://twitter.com/shadowcat_mst/status/754107237269504
  - zx2c4 14y ago
    Or try this -- http://git.zx2c4.com/memory-hemlock/tree/slow-death.c http://git.zx2c4.com/memory-hemlock/tree/slow-death.c It picks a random device on your system -- ram, video, bios, etc -- and writes a random number of random bytes into it and then sleeps for a random amount of time. Last one standing lives.
eridius 14y ago
What's /dev/sda?
- gjulianm 14y ago
  On Linux, the hard disk. This command, dd, copies data in bulk from /dev/random (a special device on *nix that outputs random bytes) to /dev/sda (your hard disk). That means it starts to overwrite your disk with trash, rendering the system unusable.
  - eridius 14y ago
    I know what `dd` is. I just don't use Linux, so I'm not particularly familiar with the Linux-specific /dev entries. Thanks though.
- aroman 14y ago
  Most probably the storage device which is your HD.
- aidos 14y ago
  Probably your main drive.
- derleth 14y ago
  The device file applications can use to access the first hard drive on most Linux systems. It provides raw access without filesystems or partitions. /dev/sda1 is the first partition on that drive, /dev/sda2 the second, and so on. /dev/sdb is the next hard drive, /dev/sdc the next after that; beyond /dev/sdz, the naming scheme is apparently dependent on the hardware driver in use: Going from /dev/sdz to /dev/sdaa is what happens in the default SATA and SCSI drives, up to /dev/sdzzz, at which point you apparently run into problems. [1] http://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-named-beyond-drive-26-devsdz/ http://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-na... [1] http://kerneltrap.org/mailarchive/linux-scsi/2010/9/20/6886603 http://kerneltrap.org/mailarchive/linux-scsi/2010/9/20/68866...
huherto 14y ago
Aahhh. In the old days, we used this command just to mess with your workmates. while : do clear > /dev/tty sleep 5 done
- hp50g 14y ago
  We wrote our own shell when I was at university (which was completely offensive, not at all obedient and generally no help whatsoever) and chsh'ed them if they left a terminal open :) (for ref, we had to do very naughty things to SunOS 4 to add it to /etc/shells)
  - jimfl 14y ago
    /usr/games/worms is the best shell ever.
    - hp50g 14y ago
      Never thought of that - great suggestion :)
RyanGWU82 14y ago
It's not so funny when you do this accidentally, on a 2 TB disk full of user data, on a live production server, at 2AM on a Friday night... (The server was part of a MogileFS cluster so there were multiple copies of the data online. There was no data loss, not even any downtime. Still, it was scary as hell, and I spent all Saturday in the data center restoring the box.)
- xyos 14y ago
  how did you end up doing this accidentally?
  - niggler 14y ago
    I've seen stranger: a redirect gone the wrong way $ foo < bar # runs command `foo`, reading from `bar` on stdin $ foo > bar # runs command `foo`, writing stdout to `bar` Writing `>` instead of `<` has resulted in many a blowup at 3 AM
    - huherto 14y ago
      My friend did this... rm * -i The system response was "-i not found" or something like that.
      - ISL 14y ago
        I once discovered that apparently rm bob* has completely different behavior from rm bob * The above line of code successfully fixed a bug I'd been trying to find for weeks in source code in the same directory. When I rewrote it from scratch, the bug was gone.
        niggler 14y ago
        rm -i is your friend
        14y ago
lucian303 14y ago
I've always gone with the classic: rm -rf / However, sometimes that's protected so i switch: Lazy version: rm -rf /* Long version: rm -rf / --no-preserve-root But I do like your brute force random disk wipe method. I'll try that on the next vm that's gotta go.

srl 14y ago

Back when `/dev/mem` was a thing in default kernels (now you need a special config, or a module), I enjoyed `cat /dev/urandom > /dev/mem`. That would usually bork things pretty quickly, so then I would set random offsets with `dd`. Fun times.

mikeash 14y ago
See also kmem Russian Roulette: https://twitter.com/shadowcat_mst/status/754107237269504 https://twitter.com/shadowcat_mst/status/754107237269504
- zx2c4 14y ago
  Or try this -- http://git.zx2c4.com/memory-hemlock/tree/slow-death.c http://git.zx2c4.com/memory-hemlock/tree/slow-death.c It picks a random device on your system -- ram, video, bios, etc -- and writes a random number of random bytes into it and then sleeps for a random amount of time. Last one standing lives.

eridius 14y ago

What's /dev/sda?

gjulianm 14y ago
On Linux, the hard disk. This command, dd, copies data in bulk from /dev/random (a special device on *nix that outputs random bytes) to /dev/sda (your hard disk). That means it starts to overwrite your disk with trash, rendering the system unusable.
- eridius 14y ago
  I know what `dd` is. I just don't use Linux, so I'm not particularly familiar with the Linux-specific /dev entries. Thanks though.
aroman 14y ago
Most probably the storage device which is your HD.
aidos 14y ago
Probably your main drive.
derleth 14y ago
The device file applications can use to access the first hard drive on most Linux systems. It provides raw access without filesystems or partitions. /dev/sda1 is the first partition on that drive, /dev/sda2 the second, and so on. /dev/sdb is the next hard drive, /dev/sdc the next after that; beyond /dev/sdz, the naming scheme is apparently dependent on the hardware driver in use: Going from /dev/sdz to /dev/sdaa is what happens in the default SATA and SCSI drives, up to /dev/sdzzz, at which point you apparently run into problems. [1] http://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-named-beyond-drive-26-devsdz/ http://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-na... [1] http://kerneltrap.org/mailarchive/linux-scsi/2010/9/20/6886603 http://kerneltrap.org/mailarchive/linux-scsi/2010/9/20/68866...

huherto 14y ago

Aahhh. In the old days, we used this command just to mess with your workmates. while : do clear > /dev/tty sleep 5 done

hp50g 14y ago
We wrote our own shell when I was at university (which was completely offensive, not at all obedient and generally no help whatsoever) and chsh'ed them if they left a terminal open :) (for ref, we had to do very naughty things to SunOS 4 to add it to /etc/shells)
- jimfl 14y ago
  /usr/games/worms is the best shell ever.
  - hp50g 14y ago
    Never thought of that - great suggestion :)

RyanGWU82 14y ago

It's not so funny when you do this accidentally, on a 2 TB disk full of user data, on a live production server, at 2AM on a Friday night... (The server was part of a MogileFS cluster so there were multiple copies of the data online. There was no data loss, not even any downtime. Still, it was scary as hell, and I spent all Saturday in the data center restoring the box.)

xyos 14y ago
how did you end up doing this accidentally?
- niggler 14y ago
  I've seen stranger: a redirect gone the wrong way $ foo < bar # runs command `foo`, reading from `bar` on stdin $ foo > bar # runs command `foo`, writing stdout to `bar` Writing `>` instead of `<` has resulted in many a blowup at 3 AM
  - huherto 14y ago
    My friend did this... rm * -i The system response was "-i not found" or something like that.
    - ISL 14y ago
      I once discovered that apparently rm bob* has completely different behavior from rm bob * The above line of code successfully fixed a bug I'd been trying to find for weeks in source code in the same directory. When I rewrote it from scratch, the bug was gone.
      - niggler 14y ago
        rm -i is your friend
        14y ago

lucian303 14y ago

I've always gone with the classic: rm -rf / However, sometimes that's protected so i switch: Lazy version: rm -rf /* Long version: rm -rf / --no-preserve-root But I do like your brute force random disk wipe method. I'll try that on the next vm that's gotta go.