[Trilug-ontopic] I need to create a 2 gb file using Linux
smyers at americanri.com
Fri Dec 21 13:16:19 EST 2007
Continuing the line of tricks, once you've used dd to create a file of arbitrary
size, you can use the mkfs tools on it to write a filesystem to the file, and
then you can mount it like a normal partition using the 'loop' option during the
mount. The mount manpage has some more insight on loop devices and what they're
American Research Institute
Alan Porter wrote:
>> 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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