I solved the problem of NFS depending on DNS by creating an override file in /etc/insserv/overrides/nfs-kernel-server: and running
# insserv nfs-kernel-serverto update the start up order.
My rtorrent initscript is based on this one, which does not have the dependency header that insserv requires. I used the header from the initscript included in the SABnzb+ package since it seemed reasonable that rtorrent would have the same requirements. I inserted the following into the rtorrent initscript:
### BEGIN INIT INFOand ran
# Provides: rtorrent
# Required-Start: $local_fs $network $remote_fs
# Required-Stop: $local_fs $network $remote_fs
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: rtorrent BitTorrent client
### END INIT INFO
# insserv rtorrent.shto activate the script. I didn't bother using an override file since the script is not part of a package.
And thus ended my first squeeze upgrade. Extrapolating this experience, my customer's servers, which are very heavily customized, will likely require much more work than the previous upgrade. Oh, joy!