How to create a large file

NewBudda · 06-01-2007, 02:14 AM

Hi all,
I would like to create a file that takes up a lot of disc space on Debian. Say 5 GB or more. Is there a way that I can create such a file from nothing? The reason I am asking is this: I would like to artifically fill my server after reinstallation and then shred that file to overwrite any information that might be left in the difference between a clean install and the previous install with data.
If theres a command to create a from "nothing" please let me know...

theYinYeti · 06-01-2007, 02:28 AM

dd if=/dev/zero of=/path/to/bigfile count=10000000

Yves.

dasy2k1 · 06-01-2007, 06:06 AM

try piping /dev/urandom to a file, not sure how you woudl stop it when you got to the right size tho

pixellany · 06-01-2007, 06:53 AM

Quote:

Originally Posted by dasy2k1

try piping /dev/urandom to a file, not sure how you woudl stop it when you got to the right size tho

dd is your friend

To use a pipe, you would have to do something like "cat /dev/urandom" I don't know if that's legal (and I am not about to try......

)

syg00 · 06-01-2007, 07:03 AM

Sure it is, but you wouldn't pipe it - use it instead of /dev/zero in dd.
Use a decent blocksize as well.

NewBudda · 06-01-2007, 05:38 PM

thanks YinYeti, it worked like a charm!

theYinYeti · 06-04-2007, 02:06 AM

You're welcome

Note that dd is more powerfull than my knowledge reckons

Thanks syg00 for reminding me about that. In my example, I used the default block size, which is 512 Bytes. By specifying a saner block size, you could at least simplify the computations that give you the "count" argument.
Besides, /dev/random or similar may indeed interest you if you want random content in your result file.

Yves.

Edit: see here:
http://www.linuxquestions.org/questi...d.php?t=362506