Create a large file on macOS

August 8, 2022


I won't present how to generate a valid file (audio, video, text, pdf) as the issue is more complex. Instead, we will focus on generating files of specific sizes.


2mkfile 100m test.pdf


Imagine you need to test something, and you need to have a file of a specific size (or file bigger than n MB). What would you do? You would probably try to find some files on your local drive or the internet. You will be successful after a few moments, but is it easiest to do that? What if you need to test multiple file sizes? Finding the right file with the right size would take a long time. So what are the other options, you might ask? The answer is simple - the mkfile command.

mkfile command

The official description is following:

mkfile creates one or more files that are suitable for use as NFS-mounted swap areas. The sticky bit is set, and the file is padded with zeroes by default. Non-root users must set the sticky bit using chmod(1). The default size unit is bytes, but the following suffixes may be used to multiply by the given factor: b (512), k (1024), m (1048576), and g (1073741824).

But to be honest, this description is not really beginner friendly. So what does mkfile, and how can we use it?

mkfile creates a file of a specified size with "dummy" data (You can create a file with a PDF extension, but it won't be a proper/valid PDF). To create a file, you can run the following command: mkfile 100m test.pdf. It will generate a file that will have +- 100MB, and the name will be test.pdf


Sometimes you have a "right" file for your testing; if not, instead of trying to find a proper file, create one to match your needs!

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