How can I create a 10-megabyte binary file on linux?

Question

I want to create the file to implement a I/O benchmark on linux.

Thanks in advance, Antonio

See this answer over at the Unix StackExchange: https://unix.stackexchange.com/questions/101332/generate-file-of-a-certain-size — Blaze, Oct 05 '18 at 14:30
There is the link shared above by @Blaze with the solution you want. In addition there are several other links solving this same problem. With a quick search for Satckoverflow you will find several answers. — Geraldo Novais, Oct 05 '18 at 17:03
Another link inside Stackoverflow that solves the same thing: https://stackoverflow.com/questions/139261/how-to-create-a-file-with-a-given-size-in-linux — Geraldo Novais, Oct 05 '18 at 17:14

score 0 · Answer 1 · answered Oct 05 '18 at 14:32

If you are using a filesystem which supports it, you can do this with fallocate. Here is the command line version

/tmp/tmp.tO6EDnuWXT λ > fallocate -l 10MiB derp
/tmp/tmp.tO6EDnuWXT λ > du derp
10240   derp

score 0 · Answer 2 · answered Oct 05 '18 at 14:52

0

If the contents of the file do not matter, you can do something like:

dd if=/dev/random of=./derp bs=1024 count=10000

bs is the block size, so in the above example I am creating the file in 1024 (1K) chunks, and count is how often I do this (1K * 10000 = 10M). See https://www.linuxnix.com/what-you-should-know-about-linux-dd-command/ for more examples

answered Oct 05 '18 at 14:52

thurizas

I'd suggest using */dev/urandom*, so that it doesn't get stuck if there's not enough entropy. – CristiFati Oct 05 '18 at 15:34
You might also want to update your answer (although */dev/zero* from the other questions/answers would make more sense). – CristiFati Oct 06 '18 at 01:53

2 Answers2