How to install Unstable?

["Dan H." <dunno@stoptrick.com>]

Hello,

I just tried installing Debian unstable on an extra disk I had kicking
around (I've been running stable for several years without any trouble).

This is what I did: I fetched the etch installer (there seems to be no
dedicated "unstable" installer) and installed a minimal barebones system
(bailed right out of tasksel without checking anything). Booted into
this system, and changed the relevant lines in /etc/apt/sources.list
from "etch" to "unstable". I also deleted the CD-ROM sources (which is
testing) as well as the security ones (there being no explicit security
stuff for unstable).

Then I did "apt-get update" and "apt-get dist-upgrade".

The system worked for a while; I cant't really recall what happened, and
threw a lot of errors. The "update" bit works fine, but whenever I run
"apt-get upgrade" or "apt-get dist-upgrade", I get this:

-------------------------------
Reading Package Lists...
Building Dependency Tree...
The following packages will be upgraded:
  adduser bsdmainutils bsdutils busybox console-common console-data
  coreutils cron debianutils dhcp3-client dhcp3-common dmidecode dpkg
  dselect gcc-4.1-base gzip initscripts installation-report klibc-utils
  klogd libacl1 libattr1 libc6 libc6-i686 libdevmapper1.02 libgcc1
  libgpg-error0 libklibc libnewt0.52 libreadline5 libsepol1 libstdc++6
  libusb-0.1-4 libvolume-id0 libwrap0 linux-image-2.6.18-3-486 locales
  lsb-base module-init-tools mount nano netbase openbsd-inetd
  readline-common sysklogd sysv-rc sysvinit sysvinit-utils tasksel
  tasksel-data tcpd tzdata udev util-linux vim-common vim-tiny whiptail
Preconfiguring packages ...
dpkg: configuration error: unknown option log: Success
dpkg: configuration error: unknown option log: Success
dpkg: configuration error: unknown option log: Success
dpkg: configuration error: unknown option log: Success
dpkg: configuration error: unknown option log: Success
dpkg: configuration error: unknown option log: Success
57 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B/39.5MB of archives.
After unpacking 3084kB of additional disk space will be used.
dpkg: configuration error: unknown option log: Success
E: Sub-process /usr/bin/dpkg returned an error code (2)
-------------------------------

And the system is left in a completely unusable state. I couldn't even
edit the apt sources back to "etch" because I couldn't get an editor:

# vi /etc/apt/sources.list
-bash: /usr/bin/vi: no such file or directory.

So what can I do now?

Thanks,
--Dan