Reading entropy_avail file appears to consume entropy

[Jan Ceuleers]

I'm using the 2.6.31 kernel that comes with Ubuntu 9.10.

If I

   # watch cat /proc/sys/kernel/random/entropy_avail

then the size of the entropy pool falls rapidly (by more than 200 bytes per 2s interval). It settles down around 160 bytes.

The machines on which I've done the above experiment are otherwise idle. They are also dramatically different from one another: one is a laptop, the other is an embedded device (a Soekris net5501).

Is this supposed to happen?

Thanks, Jan
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