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From Kevan Miller <>
Subject low entropy on linux systems
Date Fri, 15 Jul 2011 02:19:47 GMT
From time to time I encounter a problem starting a Geronimo server on a Linux system (I've
always seen it on Ubuntu -- but the problem could exist on other distributions). The server
start seems to hang. However, if you're patient, which I rarely am, the server will eventually
start. If you're inquisitive, and dump the stack traces of the java process, you'll see something

"main" prio=10 tid=0x0000000040c0d800 nid=0xa79 runnable [0x00007f57a04fb000]
   java.lang.Thread.State: RUNNABLE
	at Method)
	- locked <0x00000000daad63e0> (a java.lang.Object)
	- locked <0x00000000d3b5a768> (a

This problem isn't Geronimo specific. But since I see it from time to time, thought it would
be worth passing along to the community...

The Sun/Oracle-based JVM is attempting to generate a pseudo-random number to be used as a
seed for an SSL server socket. To generate the pseudo-random number, the JVM is reading from
the /dev/random device to obtain some random information for the seed. The problem is that
reads from the /dev/random device will block if the system does not have a good source of
random events. So, the Geronimo server startup is blocked waiting for enough random information
to be returned from /dev/random. This article may be help understand the basic issue --

 I'm no security expert. And I don't know the potential implications, but the simplest way
that I've found to avoid the problem is to use the /dev/urandom device, instead of /dev/random.
Do this by specifying the following java property ''.
So, the following should work well:

$ GERONIMO_OPTS="" ./geronimo run --long

Note to self -- would be nice to record this on our Wiki somewhere. Anyway, hope this is useful...


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