fallocate -l 1G 1GBybe.testfile; # with fallocate

dd if=/dev/urandom of=1GBybe.testfile bs=64M count=16 iflag=fullblock; # generate 1GByte test file that contains random data

https://www.cyberciti.biz/faq/howto-create-lage-files-with-dd-command/

https://superuser.com/questions/470949/how-do-i-create-a-1gb-random-file-in-linux

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