this post was submitted on 24 May 2025
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cat /proc/sys/kernel/random/uuid [I ❤️ Linux] (feddit.org)
submitted 3 days ago* (last edited 2 days ago) by [email protected] to c/[email protected]
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That's all. I just found this in a random script. Generates a random UUID every time it's called. I didn't know.

Of course I can also use uuidgen or pipe /dev/(u)random into something to get a random alphanumeric string - but this is built right into the kernel!

In /proc/sys/kernel/random/, there's also boot_id which ~~seems to do the same~~ is static, and some tweakable parameters.

❤️🐧

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[–] [email protected] -1 points 2 days ago (2 children)

See also: /dev/null

It’s basically a black hole where you can throw anything.

[–] [email protected] 10 points 2 days ago (1 children)

Yes, but what if it were a subscription? May I present: /dev/null-as-a-Service.

[–] [email protected] 1 points 1 day ago

The most secure Bitcoin endpoint yet!

lol.

Okay, let’s be honest, it’s basically a crappy Pentium 4 box with Debian and nginx installed.

[–] [email protected] 9 points 2 days ago* (last edited 2 days ago) (5 children) 
cat /proc/sys/kernel/random/uuid > /dev/null
[–] [email protected] 16 points 2 days ago (4 children)

Would have to be cat /proc/sys/kernel/random/uuid > /dev/null

You can't pipe to a file, only to programs, and since /dev/null isn't an executable your command will simply give an error.

To make it more clear, consider using dd, which lets you explicitly specify an input and output file. For example: dd if=/proc/sys/kernel/random/uuid of=/dev/sda1 wait shit that wasn't the right output oh god oh fu

[–] [email protected] 2 points 2 days ago

dd is just cp but more confusing here.
The only thing dd can do that cp can't is stop ahead of time, which only really matters for infinite files like /dev/random

cp /proc/sys/kernel/random/uuid /dev/sda

[–] [email protected] 1 points 2 days ago

dd if=/proc/sys/kernel/random/uuid of=/dev/sda1

Peanuts. Real men do dd if=/proc/sys/kernel/random/uuid of=/dev/sda

[–] [email protected] 1 points 2 days ago* (last edited 2 days ago)

Thanks, I'm overworked lately.

lol, the last part

[–] [email protected] 2 points 2 days ago

i saw this and came to do THE THING but you beat me too it. GOOD ANYA

[–] [email protected] 3 points 2 days ago* (last edited 2 days ago)

while :; do cat /proc/sys/kernel/random/uuid > /dev/null; done

edit: on all cores for maximum "efficiency"

[–] [email protected] 3 points 2 days ago (1 children)

The information will be evenly distributed upon its surface and some believe one day it will be be radiated back out into the rest of the system.

[–] [email protected] 2 points 2 days ago

That's a horrifying concept. Better not think about it.

[–] [email protected] 1 points 2 days ago (3 children)

That reminds me of the CPU stress test I ran many years ago.

dd if=/dev/random of=/dev/null

If you have 8 cores, just open 8 terminals, and run that code in each of them.

[–] [email protected] 2 points 2 days ago (1 children)

Can you guarantee that each process will run on its own core?

[–] [email protected] 2 points 2 days ago

Absolutely not, quite the opposite actually. However, the end result is close to 100% CPU load, which is good enough for some purposes. Let’s say you want to test the performance of your CPU cooler, or overclock stability, this should good enough. There are also dedicated tools for people with more advanced needs.

[–] [email protected] 4 points 2 days ago

/dev/urandom should stress the CPU more. /dev/random can be entropy limited

[–] [email protected] 3 points 2 days ago* (last edited 2 days ago) (1 children) 
for i in {1..n}  # where n == number of cores
do
  dd if=/dev/urandom of=/dev/null &
done

# to stop:
jobs -p | xargs kill
[–] [email protected] 1 points 2 days ago (1 children)

Oh yeah. This looks like a much better way to do it. My solution is pretty bare bones by comparison.

[–] [email protected] 1 points 2 days ago

the advantage of yours is that you can actually see the performance number afterwards.