[Trilug-ontopic] I need to create a 2 gb file using Linux

Alan Porter porter at trilug.org
Fri Dec 21 10:13:39 EST 2007

> Yeah, thanks, it worked great.  Created a one gig file but it wasn't 
> long before I got the file size I wanted.  Thanks again!!!

Another trick... you can create a so-called "sparse" file by doing this:

dd if=/dev/zero of=/home/alan/myfile bs=1 count=0 seek=2G

That takes something like a millisecond to create.  It does not waste 
time copying 2 billion bytes to a file.

The space for the file is not actually allocated on the disk until some 
actual data is written to it, and even then it is only allocated as 
needed.  If you read the file, it would look like all zeros.

This is useful if you just want to create an image for something without 
waiting (for example, create an image and then immediately cover it up 
with a filesystem or something).  However, this method is NOT useful 
when you're trying to test what happens when a disk is full, since it 
does not actually fill up the disk.

Something neat to add to the toolbox...



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