I think the raspberry pi disk image that is available is 2GB, so it's probably easiest if you have at least that.

On 10 October 2014 09:41, Brian L. Stuart <blstuart@bellsouth.net> wrote:
> I'm new to Plan9, using acme/p9p for a couple of months, and
> I want to add plan9 machines to my network. I'm thinking
> that a DNS/DHCP/AUTH server will be an easy step. If this
> machine could have the role of an Internet
> firewall/nat-router it will be even better.
>
> Do you think plan9+raspi can handle this?

While I haven't set one up like this myself, I'm tempted to do so.
I expect the Pi would make a very nice little auth/dhcp/etc
server.  However, to my knowledge, there aren't any NAT
implementations available on Plan 9.  I know it's been worked
on by several people at different times, but I don't think anyone
has a currently packaged implementation.

> What is the recommended size for the SD card for this role?

The databases used for these functions are pretty small, so
I'd be surprised if you filled a 1G card.

BLS