问题
The question have been asked in here http://www.gossamer-threads.com/lists/linux/kernel/1210167 but I don't see an answer.
AFAIK /proc/sys/kernel/random/entropy_avail should return the size of available entropy but should not consume it. At least I don't see any reason for that.
However, I have been noticing the same thing as OP for at least a year and now I executed in quick succession
% cat /proc/sys/kernel/random/entropy_avail
3918
% cat /proc/sys/kernel/random/entropy_avail
3447
% cat /proc/sys/kernel/random/entropy_avail
2878
% cat /proc/sys/kernel/random/entropy_avail
2377
% cat /proc/sys/kernel/random/entropy_avail
1789
% cat /proc/sys/kernel/random/entropy_avail
1184
% cat /proc/sys/kernel/random/entropy_avail
577
% cat /proc/sys/kernel/random/entropy_avail
161
% cat /proc/sys/kernel/random/entropy_avail
133
% cat /proc/sys/kernel/random/entropy_avail
171
a while later I did the same with the same result, so I'm pretty sure the depletion of entropy is caused by the cat command.
Can anyone explain why this happens?
回答1:
Found an answer in here http://blog.flameeyes.eu/2011/03/entropy-broken
Starting a process consumes entropy
来源：https://stackoverflow.com/questions/13170334/reading-entropy-avail-file-appears-to-consume-entropy