Robotic Tendencies
The personal blog of Robert McQueen

September 25, 2005

Missing entropy

One of my servers has apache2 and mod_perl on it to play with some crazy stuff like dyamically looking up virtual hosts in postgres, but every time I restart apache2 for whatever reason, it blocks reading /dev/random and never starts up. A little research shows this is mod_perl trying to initialise its UUID generator with some quality system entropy (why? is it strictly necessary? are the UUIDs that important?). The problem is, it never succeeds because this machine never has any entropy:
$ cat /proc/sys/kernel/random/poolsize
512
$ cat /proc/sys/kernel/random/entropy_avail
0

It’s a headless box with no serial, mouse, keyboard or USB devices, so the only IO it sees is disk and network. How do I find out what’s eating all the entropy, or does it in fact just never have any due to nothing feeding it in the kernel? What can I do to identify and address the actual source of the problem (ie not just making /dev/random a link to /dev/urandom or patching mod_perl to just read /dev/urandom or use /proc/sys/kernel/random/uuid to make its UUIDs)?

posted by Robert McQueen @ 12:35 am
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