Linux – How to create a 1GB random file in Linux


I am using the bash shell and would like to pipe the out of the command openssl rand -base64 1000 to the command dd such as dd if={output of openssl} of="sample.txt bs=1G count=1.
I think I can use variables but I am however unsure how best to do so. The reason I would like to create the file is because I would like a 1GB file with random text.

Best Answer

if= is not required, you can pipe something into dd instead:

something... | dd of=sample.txt bs=1G count=1

It wouldn't be useful here since openssl rand requires specifying the number of bytes anyway. So you don't actually need ddthis would work:

openssl rand -out sample.txt -base64 $(( 2**30 * 3/4 ))

1 gigabyte is usually 230 bytes (though you can use 10**9 for 109 bytes instead). The * 3/4 part accounts for Base64 overhead, making the encoded output 1 GB.

Alternatively, you could use /dev/urandom, but it would be a little slower than OpenSSL:

dd if=/dev/urandom of=sample.txt bs=1G count=1

Personally, I would use bs=64M count=16 or similar:

dd if=/dev/urandom of=sample.txt bs=64M count=16