Subject: Re: r/o filesystem restrictions for firewall?
To: Jon Lindgren <>
From: Berndt Josef Wulf <>
List: port-sparc
Date: 10/24/2000 09:24:12
Jon Lindgren wrote
> I finally have a spare sparc to use as a true firewall.  I'm planning to
> burn a CD for this sucker to boot from.  I don't want it to have local 
> mass storage (besides the cd...).
> I've been looking around at regular processes which run and require
> temporary files, such as the daily security items, etc...  I figure I can
> knock syslog stuff to a remote machine, I'll be disabling mail and other
> audit scripts (hmmm....), but what about items such as /var/log/wtmp and
> such?
> So the 1e6 dollar question is: does anyone have any ideas what other
> subsystems may be affected by having a r/o local filesystem when running
> multiuser?  I've been able to experiment for a few hours or so, but I've
> not run the thing for months yet...
> Any ideas, tips, etc... are well appreciated.

Maybe not what you want...

Create the desired filesystem, place it onto a bootable CD and have it
union-mount with a filesystem on a harddisk just large enough to hold
writeable files such as logfiles etc.

Alternatively, if memory isn't much of a problem, create a CD with the
desired filesystem and have it boot into a memory-based filesystem.

Should the system be comprimised or falling over, its a matter of
seconds to reboot and have it up and running again.

I don't know about your reasons of not using a local harddisk, but
if it is for security reasons, there is nothing stopping anyone
breaking into the firewall on any type of system if the opportunity
exists due to a flaw in operating system or application.

cheerio Berndt
Name    : Berndt Josef Wulf            | +++ With BSD on Packet Radio +++
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