Any doc reference on /entropy file ?

[RW]

On Tue, 16 Dec 2008 14:08:10 +0100
Bernard Dugas <bernard at dugas-family.org> wrote:

> Hi,
> 
> When i look at / in a standard installation like :
> FreeBSD XXX 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Sun Feb 24 19:59:52
> UTC 2008     root at logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
> i386
> 
> There is only 1 file, named entropy :
> 
> -rw-------   1 root  wheel  4096 Dec 11 17:36 entropy
> 
> I can't find any reference to that file in FreeBSD doc.
> 

It contains random numbers that are written-out at shutdown and used to
seed /dev/random on the next boot.

> 
> Do i have to keep it read/write ? Can i put it in /var instead of /
> to be able to keep / read-only ?

It has to be on the root-partition, if it's going to be used. 

You can set entropy_file=NO if you don't want it. There are additional
entropy files under /var, and the system generates it's own entropy
during the boot stage, which is good enough for normal cases.