Date: Mon, 7 Feb 2005 12:25:47 +0000 (GMT) From: Jan Grant <Jan.Grant@bristol.ac.uk> To: Jay Moore <jaymo@cromagnon.cullmail.com> Cc: Gert Cuykens <gert.cuykens@gmail.com> Subject: Re: what is /entrophy ? Message-ID: <Pine.GSO.4.61.0502071222120.26752@mail.ilrt.bris.ac.uk> In-Reply-To: <200502061721.27613.jaymo@cromagnon.cullmail.com> References: <ef60af090502020352556db801@mail.gmail.com> <200502061721.27613.jaymo@cromagnon.cullmail.com>
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On Sun, 6 Feb 2005, Jay Moore wrote: > On Wednesday 02 February 2005 05:52 am, Gert Cuykens wrote: > > > what is /entrophy ? can i delete it ? > > I believe it is a mis-spelled version of /entropy Your computer attempts to collect "randomness" by sampling the timings of various physical events. That's what the /dev/random device provides: this kernel-harvested randomness. Various cryptographic systems require a supply of "good" random numbers in order to operate. When the machine first boots, the kernel's entropy pool is empty. It would consequently take potentially quite a few minutes to harvest sufficient randomness from interrupts in order to satisfy the needs of such things as sshd. The solution is the /entropy file: when the machine shuts down, it saves "spare" random bits that have not yet been used into this file. On reboot, the kernel's random pool is reinitialised using these "spare" bits. Assuming nobody's sneaked a peek at them in the itme the machine's been turned off, this is a reasonable way to quickly satisfy the startup requirements for randomness. -- jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/ Tel +44(0)117 9287864 or +44 (0)117 9287088 http://ioctl.org/jan/ You see what happens when you have fun with a stranger in the Alps?
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