If I recall correctly:

    dd if=/dev/urandom of=/home/myrandomfile bs=1 count=N

▲ bugfix 9 hours ago | parent | next [-]

I just use fallocate to create a 1GB or 2GB file, depending on the total storage size. It has saved me twice now. I had a nasty issue with a docker container log quickly filling up the 1GB space before I could even identify the problem, causing the shell to break down and commands to fail. After that, I started creating a 2GB file.

▲ tdeck 9 hours ago | parent | prev | next [-]

Fwiw you can also do this with

    head -c 1G /dev/urandom > /home/myrandomfile

And not have to remember dd's bizarre snowflake command syntax.

▲ Twirrim 17 hours ago | parent | prev | next [-]

If you want to do it really quickly

    openssl enc -aes-256-ctr -pbkdf2 -pass pass:"$(date '+%s')" < /dev/zero | dd of=/home/myrandomfile bs=1M count=1024

Almost all CPUs have AES native instructions so you'll be able to produce pseudorandom junk really fast. Even my old system will produce it at about 3Gb/s. Much faster than urandom can go.

▲ ape4 16 hours ago | parent [-]

That's very cool. Sadly running that exact command gets an incomplete file and error "error writing output file". It suggests adding iflag=fullblock (to dd). Running that makes a file of the correct size. But still gives "error writing output file". I suppose that occurs because dd breaks the pipe.

	▲	Twirrim 10 hours ago \| parent [-]
		Weird, I could have sworn that used to work, maybe I wrote the notes down wrong. Easiest alternative I guess is to pipe through head. It still grumbles, but it does work `openssl enc -aes-256-ctr -pbkdf2 -pass pass:"$(date '+%s')" < /dev/zero \| head -c 10M > foo`

▲ dotancohen 4 hours ago | parent | prev | next [-]

My choice has always been `shred`:

  $ sudo truncate --size 1G /emergency-space
  $ sudo shred /emergency-space

I find it widely available, even in tiny distros.

▲ fragmede 18 hours ago | parent | prev [-]

bs=1 is a recipe for waiting far longer than you have to because of the overhead of the system calls. Better bs=N count=1

▲

__david__ 17 hours ago | parent | next [-]

That’s also not great if you’re trying to make a 10 gigabyte file. In that case, use bs=1M and count=SizeInMB.

	▲	marcosdumay 17 hours ago \| parent [-]
		Modern computers are crazily overengineered... Most current desktops (smaller than your usual server) won't have any problem with the GP's command. Yours is still better, of course.

▲

17 hours ago | parent | prev [-]

[deleted]