7

We're investigating some JDBC issues, and one of the possible problems is /dev/random being exhausted. The workaround is to switch the JVM to using /dev/urandom, but I wan't to try and determine whether or not the /dev/random is being exhausted.

Is there a way to check if the entropy pool is being exhausted? I've gone hunting for nagios plugins and general bash commands, but I've turned up nothing.

9

Sure! Ask /proc/sys/kernel/random/entropy_avail.

  • But... every time I run that I lose entropy! – Andrew Aug 9 '13 at 2:19
  • @Andrew: There's no reason why you should. – David Schwartz Aug 9 '13 at 2:36
  • @David. Entropy does reduce as you run cat /proc/sys/kernel/random/entropy_avail, but only to a point, it will then level out and hover at around the same level – GeoSword Aug 9 '13 at 8:53
  • Perfect, exactly what I was looking for, cheers. – Josh Smeaton Aug 9 '13 at 14:25
2

as read someplace else... each new process get entropy from /dev/random

a simple way to avoid stealing the pool is a program, such as:

#!/usr/bin/env python

import time

while True:
    with open('/proc/sys/kernel/random/entropy_avail', 'r') as f:
        print(f.read().rstrip())
    time.sleep(1.0)
  • 1
    more easy: watch cat /proc/sys/kernel/random/entropy_avail – David Muñoz Jun 16 '18 at 22:51

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