FreeBSD's embedded agenda

[Jim Thompson]

On May 30, 2006, at 12:35 PM, Chad R. Larson wrote:

> On Tue, May 30, 2006 at 06:30:45AM +0100, James Mansion wrote:
>> The scenario would seem to be:
>>  - very small form factor and cost per unit
>>  - so no physical spinning disk
>>  - *and* you need a lot of updates
>>
>> Its the last of these that bears scrutiny.
>
> I've been using m0n0BSD on Soekris hardware.  The "disk" is a CF
> card, and booting consists of creating a RAM drive and then
> populating it from the CF.  The CF stays mounted R/O unless some
> persistant information (like, configuration) needs to be saved, at
> which time it is remounted R/W until the update is completed and
> then put back to R/O.

Systems with soldered on flash could hold the 'configuration' in a  
small number of flash sectors, with a checksum.
If the checksum doesn't match, then a 'default' configuration could  
be used (stored in the RO part of the flash).

m0n0 and pfsense largely point the way here, though PHP is a big  
footprint for a system with minimal flash.

> This satisfies the "no moving parts" and small form factor issues.
>
> It seems to me that if the VM could/would be willing to do its
> demand paging off the CF, so RAM would only have to hold dirty pages
> that we'd hit the sweet spot for embedded systems of small to medium
> production runs.  Especially since CF is now available in gigabyte
> sizes.

Not all embedded projects use boards that can use CF.