After upgrading a VE to Jaunty through do-release-upgrade, the network stopped working.
A post in the OpenVZ forum suggests a fix that works for me:
On the host:vzctl set XXX --features "sysfs:on" --save
In the container:vi /etc/init.d/networking
After the comments at the top, add the line:mkdir -p /var/run/network
Note the post suggested the directory var/run/networking, my init script wanted /var/run/network for some reason. I also added -p to mkdir.
Presumably, there’s a smoother solution creating the directory through the OpenVZ init scripts.
Update: Here’s a more detailed explanation of what’s going on.