DEV Community

Devtonight
Devtonight

Posted on • Originally published at devtonight.com

How To Create Extra Large Dummy Files Quickly With Linux

Create a 1GB dummy file using the dd command in your home directory.

dd if=/dev/random of=$HOME/dummy.data bs=1MB count=1024
Enter fullscreen mode Exit fullscreen mode

The problem with the dd command is it takes a considerable amount of time to create the file. Especially, if you are creating a large file with dozens of gigabytes it will take a considerable amount of time to write the file. For that kind of situation, we can use the fallocate command. It will create a 10GB file within 1~2 seconds.

fallocate -l 10G dummy.data
Enter fullscreen mode Exit fullscreen mode

Important! fallocate command does not work on ZFS and Ext3 file systems.

In addition to the above examples, there is another way to create a large file in Linux using the truncate command. This truncate command is quite strange, it will create a 50GB file within 1~2 seconds, but surprisingly it will not take such a disk space. So we tried to create a whopping 15TB (Terabyte) file and it worked.

truncate -s 15T dummy.data
Enter fullscreen mode Exit fullscreen mode

Discussion (0)