Comment 7 for bug 1435416

This will need to be fixed in trusty too:

https://github.com/lxc/lxc/issues/735

a trusty lxd container on a wily or newer host will fail to start nested containers.

workarounds include

apt-get -t trusty-backports install cgmanager

or setting lxc.cgroup.use in /etc/lxc/lxc.conf to not include the co-mounted controllers, i.e.

lxc.cgroup.use = devices,name=systemd,freezer,memory