As I upgraded from slink to potato, I believe an interactive comment mentioned that 2.2.* kernels (I run kernel 2.2.16) need no explicit loopback. Because of my selection, the upgrade script produced a file /etc/network/interfaces with all lines commented. In particular, this "interfaces" file had the following line # iface lo inet loopback not iface lo inet loopback UNCOMMENTING THIS LINE GOT MY SYSTEM WORKING AGAIN.
Before this, I could no longer use my modem for ppp connnections, my domain server failed lookups, and for 5 hours I concentrated on failure of the package nfs-common. In particular, in the script /etc/init.d/nfs-common, a line with /sbin/rpc.lockd failed. Later, I thought my local bind/named was failing from the upgrade. This extensive failure I saw arose, as I said above, from the default /etc/network/interfaces. I first saw this error as an NFS problem, since booting hung there for about three minutes. However, from the boot log in /var/log/messages, Jul 19 21:17:06 rabbit kernel: Adding Swap: 128484k swap-space (priority -1) Jul 19 21:17:06 rabbit kernel: Adding Swap: 128484k swap-space (priority -2) Jul 19 21:17:06 rabbit kernel: eth0: Setting full-duplex based on MII#0 link partner capability of 05e1. Jul 19 21:17:06 rabbit kernel: RPC: sendmsg returned error 101 Jul 19 21:17:06 rabbit kernel: neighbour table overflow Jul 19 21:17:07 rabbit kernel: neighbour table overflow Jul 19 21:17:11 rabbit kernel: RPC: sendmsg returned error 101 Jul 19 21:17:36 rabbit last message repeated 2 times Jul 19 21:17:56 rabbit kernel: portmap: server localhost not responding, timed out Jul 19 21:17:56 rabbit kernel: RPC: sendmsg returned error 101 Jul 19 21:18:26 rabbit last message repeated 3 times Jul 19 21:18:46 rabbit kernel: portmap: server localhost not responding, timed out Jul 19 21:18:46 rabbit kernel: lockd_up: makesock failed, error=-5 Jul 19 21:18:46 rabbit kernel: RPC: sendmsg returned error 101 Jul 19 21:19:16 rabbit last message repeated 3 times Jul 19 21:19:36 rabbit kernel: portmap: server localhost not responding, timed out Jul 19 21:19:37 rabbit kernel: neighbour table overflow