cat /proc/sys/kernel/random/uuid [I ❤️ Linux]
cat /proc/sys/kernel/random/uuid [I ❤️ Linux]
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.
❤️🐧
My guy you've just given me the same sense of wonder you got yourself. Fuck man I love linux
When writing shell scripts that run in a loop I always look for files in /sys or /proc before using standard utilities. There's a lot
- /proc/mounts instead of the mount command
- /sys/class/..../backlight to influence screen brightness
- /sys/class/net to get info and stats about interfaces
- ....
Someone should make a comprehensive list I guess.
boot_idseems to be static, probably set at boot.
So don't use it for a random uuid.it's fine as long as you reboot before each call
Oops you’re correct. Editing OP.
Interesting,
non-scientific speed test:kernel 6.1.0-37-amd64:
$ time for i in $(seq 1 100000); do cat /proc/sys/kernel/random/uuid > /dev/null; done real 3m53,388s user 1m37,366s sys 2m13,847s $ for i in $(seq 1 100000); do cat /proc/sys/kernel/random/uuid ; done | wc -l 100000vs.
uuid1.6.2-1.5+b11:$ time for i in $(seq 1 100000); do uuid -v4 > /dev/null; done real 4m44,854s user 1m37,867s sys 3m4,414s $ for i in $(seq 1 100000); do uuid -v4 ; done | wc -l 100000EDIT: I'm blind (wrong result).
Yeah but please don't actually use this. Use a proper UUID library that works cross-platform and lets you choose the UUID type and can be seeded etc.
Can you explain?
Use for what?
Also it is being seeded, according to the fileurandom_min_reseed_secswhich is also writeable. Here are the other files:-r--r--r-- 1 root root 0 25. 5. 11:13 boot_id -r--r--r-- 1 root root 0 25. 5. 11:19 entropy_avail -r--r--r-- 1 root root 0 25. 5. 11:19 poolsize -rw-r--r-- 1 root root 0 25. 5. 11:19 urandom_min_reseed_secs -r--r--r-- 1 root root 0 25. 5. 11:19 uuid -rw-r--r-- 1 root root 0 25. 5. 11:19 write_wakeup_thresholdedit: the type is always DCE/random
This is awesome. Thank you
Thank you so much for sharing this!
Works in Termux on Android
See also: /dev/null
It’s basically a black hole where you can throw anything.
Yes, but what if it were a subscription? May I present: /dev/null-as-a-Service.
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.
cat /proc/sys/kernel/random/uuid > /dev/nullWould have to be
cat /proc/sys/kernel/random/uuid > /dev/nullYou 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/sda1wait shit that wasn't the right output oh god oh fuwhile :; do cat /proc/sys/kernel/random/uuid > /dev/null; doneedit: on all cores for maximum "efficiency"