Create Large File Using fallocate

If you need to create a large test file on Linux, fallocate can help.

To create a 1GB file:

fallocate -l 1G test.img

If you need a different size, just change the -l option with the proper suffix.

If your operating system does not support fallocate, you can always rely on the dd command.

To create a 1GB file:

dd if=/dev/zero of=/path/to/your/output/file bs=1024 count=1024000

Since dd is more complicated, here are what these inputs mean:

if= is your input, we’re using /dev/zero to generate junk data.
of= is your output.
bs= is the number of bytes read and written at a time.
count= is the number of input blocks we are copying, or how many times we want to run the bs= input.

Based on the above inputs, you just need to change the value of count= to increase/decrease the file size.