Subject: Re: duty cycles on compact flash?
To: Steven M. Bellovin <>
From: Marcin Jessa <>
List: tech-embed
Date: 10/12/2005 11:52:19
On Wed, 12 Oct 2005 05:37:34 -0400
"Steven M. Bellovin" <> wrote:

> In message <>, Marcin Jessa
> writes:
> >On Tue, 11 Oct 2005 21:58:15 -0400
> >"Steven M. Bellovin" <> wrote:
> >
> >> How many times can a typical CF card be written?
> >
> >That does not really metter as long as you mount your /var and /tmp
> >as memory file system. The leases will never get written to your CF
> >then. That's basically what people do working with media like CFs.
> Right, but that conflicts with the dhcp spec.  RFC 1531 says that a 
> server "must retain host configuration across server reboots, and,
> whenever possible, a host should be assigned the same configuration
> parameters despite restarts of the DHCP mechanism".  No, this doesn't
> matter that much, since it's for my house; I'd still like to do it
> properly.

Then write a script to backup your lease file when rebooting and
restore it before you bring your dhcpd back.
That way you will not write that often to the CF.

> >> I'm going to build a gateway from a Soekris 4801.  I may want to
> >> use it as a DHCP server, in which case I'd like to use non-volatile
> >> storage for the lease database.  How long could I expect it to
> >> last?
> >
> >Marcin.
> >
> >P.S I have a system which does what you want.
> >Let me know if you want to try it out.
> >
> That would spoil my fun....

Yeah :)
If you need some jumpstarting I have written a doc as well gathered a
few ones about building an embedded system with NetBSD at