I achieved this through the following steps:
- found a prepackaged sarge image at virtualboxes.org (http://virtualboxes.org/images/debian/) -- here's the link to the actual image: http://downloads.sourceforge.net/virtualboximage/debian-3.1r0a-x86-netinstall-2.7z
- using 7-zip, extract the VDI file from the image, put it in the Virtualbox directory (there are some other files in the 7z archive, like an XML file describing the VM, but these can be discarded)
- in Virtualbox, go to Files->Virtual Media Manager and create a new disk (use existing image)
- create a new virtual machine (Linux, Debian) with 384 Mb of memory using the disk just created. Also I suggest turning off: ACPI (Linux kernel 2.4 doesn't support it), USB and Sound Card - assuming you don't need them. This speeds up the VM boot process.
- fire up the new VM. At the Debian 3.1 login prompt, log in as "root/toor" - I went ahead and appended "root-toor" to the VM name in Virtualbox, just in case I forget the root password.
- Now, here's an important caveat: out of the box, the server line in /etc/apt/sources.list does not work. I had to change that line to:
deb http://archive.debian.org/debian/ sarge main
(this is the only line needed in the file - all other lines should be deleted or commented out)
- For awhile this worked fine. But then, for some reason, the address archive.debian.org got associated with an unresponsive IP address. From another machine, I nslookuped it and got the IP address "18.104.22.168", which was responding to pings. So I added the line "22.214.171.124 archive.debian.org" to /etc/hosts
- "apt-get update" worked at this point
- Then I ran "apt-get upgrade" to upgrade to the final revision of Debian 3.1 "sarge"
- At this point I had a working minimal system.