The 7 Deadly Linux Commands

[sharks]

The 7 Deadly Linux Commands
http://www.junauza.com/2008/11/7-deadly-linux-commands.html

[damis648]

Ah, I thought the forkbomb was just called "fork". Good to know! :-)

EDIT: Wait... can you mv something to /dev/null? (Command 7) Will it even let you do that? You can't mv anything into a file...

[saulgoode]

EDIT: Wait... can you mv something to /dev/null? (Command 7) Will it even let you do that? You can't mv anything into a file...
You can do it (assuming you have root privileges), but the results won't be immediately disastrous. Your /dev/null device will be replaced by a file, which will probably cause problems if you ever try to use /dev/null as a source of (what should be) zeros. In the more typical case of redirecting output to /dev/null, performance will harmed -- /dev/null should normally be something of a no-op -- and you could conceivably fill up your / device (i.e., the hard drive). Deleting the 'null' file and rebooting should correct things (or you could manually use 'mknod' to recreate the null device).

[TBOL3]

You know, I applaud everyone for helping with this cause, but wouldn't it be better if people just didn't use a command, unless they new what it was doing? (Except for shell scripts, for those, I gues you either have to read it all, or just trust the source).

[iponeverything]

You can do it (assuming you have root privileges), but the results won't be immediately disastrous. Your /dev/null device will be replaced by a file, which will probably cause problems if you ever try to use /dev/null as a source of (what should be) zeros. In the more typical case of redirecting output to /dev/null, performance will harmed -- /dev/null should normally be something of a no-op -- and you could conceivably fill up your / device (i.e., the hard drive). Deleting the 'null' file and rebooting should correct things (or you could manually use 'mknod' to recreate the null device).


mv something /dev/null = rm something

/dev/null is not modified or changed in any way. And from low level file system perspective - I believe - they do the exact same thing. The former, for me, is like picking up a piece of data an putting it in the trash can and latter is like using a antimatter gun to disintegrate something.

BTW -- anyone can put stuff into /dev/null not just root.

[saulgoode]

mv something /dev/null = rm something

/dev/null is not modified or changed in any way. And from low level file system perspective - I believe - they do the exact same thing. The former, for me, is like picking up a piece of data an putting it in the trash can and latter is like using a antimatter gun to disintegrate something.

If the last argument of the 'mv' command exists and is not a directory, it is treated as a file and the attempt is made to replace it with the source file.

$ echo "replaced" >sourcefile
$ echo "original" >destfile
$ cat destfile
original
$ mv sourcefile destfile
$ cat destfile
replaced


BTW -- anyone can put stuff into /dev/null not just root.
Nonetheless, only 'root' has permission to remove, rename, or create files in the /dev directory:

$ ls -ld /dev
drwxr-xr-x 17 root root 14660 2008-11-20 22:02 /dev/

[iponeverything]

If the last argument of the 'mv' command exists and is not a directory, it is treated as a file and the attempt is made to replace it with the source file.

$ echo "replaced" >sourcefile
$ echo "original" >destfile
$ cat destfile
original
$ mv sourcefile destfile
$ cat destfile
replaced


Nonetheless, only 'root' has permission to remove, rename, or create files in the /dev directory:

$ ls -ld /dev
drwxr-xr-x 17 root root 14660 2008-11-20 22:02 /dev/

You are right. I don't know if it just my faulty memory or if things really changed somewhere along the line. I should have just gave it quite test at the command line, before adding my 2 cents.

[schauerlich]

Is it just me or was most of that lifted from jdong's announcement?

http://ubuntuforums.org/announcement.php?f=11

[kernelhaxor]

Is it just me or was most of that lifted from jdong's announcement?

http://ubuntuforums.org/announcement.php?f=11


I don't think it is necessarily lifted from one place or the other .. they're jus common and known for their bad nature.. so you will find them in a lot of places (in the form of warnings I mean) ..

[schauerlich]

I don't think it is necessarily lifted from one place or the other .. they're jus common and known for their bad nature.. so you will find them in a lot of places (in the form of warnings I mean) ..

Not only are the commands the same, the descriptions are too. It's pretty obvious this guy just slightly reworded jdong's announcement.


Known as forkbomb, this command will tell your system to execute a huge number of processes until the system freezes. This can often lead to corruption of data.


Forkbomb: Executes a huge number of processes until system freezes, forcing you to do a hard reset which may cause corruption, data damage, or other awful fates.


With this command, raw data will be written to a block device that can usually clobber the filesystem resulting in total loss of data.


Block device manipulation: Causes raw data to be written to a block device. Often times this will clobber the filesystem and cause total loss of data