Comment 2 for bug 885909

This turns out to have been a result of the following line in /etc/network/interfaces:

up flush-mail

Removing this line allows the ifup command to complete and fully configure the eth0 interface, which does emit the necessary events to allow the boot process to continue.

Messages alerting the failure of ifup are hidden by the wonder of the upstart scripting, so there is no warning that the network interface (which seemed to work fine) was only partially configured/started.

At some point, it seems the flush-mail command has been removed by an upgrade, the up command crashes, ifup ends prematurely, no warning...

Perhaps hiding all the detail of startup by writing to /dev/null is not such a clever idea?

Owen