[Linux 常見問題] Quickly create a large file on a Linux system

 Source From Here

Question
How can I quickly create a large file on a Linux (Red Hat Linux) system?

dd 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.

How-To
dd from the other answers is a good solution, but it is slow for this purpose. In Linux (and other POSIX systems), we have fallocate, which uses the desired space without having to actually writing to it, works with most modern disk based file systems, very fast. For example:

# fallocate -l 10G gentoo_root.img