Quickly create a large file on a Linux system?

Question

How can I **quickly** create a large file on a Linux ([Red Hat Linux][1]) system? [dd][2] will do the job, but reading from `/dev/zero` and writing to the drive can take a long time when you need a file several hundreds of GBs in size for testing... If you need to do that repeatedly, the time really adds up. I don't care about the contents of the file, I just want it to be created quickly. How can this be done? Using a sparse file won't work for this. I need the file to be allocated disk space. [1]: http://en.wikipedia.org/wiki/Red_Hat_Linux [2]: http://en.wikipedia.org/wiki/Dd_%28Unix%29

Answer 1

Hi, if you have 'fallocate' available in your Unix, it will be much faster. Something like:

# fallocate -l 400GB /tmp/bigfile

Of course make sure the target directory has that much space available.

Cheers,

j