Update
As of docker 0.9, for the steps below to now work, one now has to update the /etc/default/docker
file with the '-e lxc'
to the docker daemon startup option before restarting the daemon (I did this by rebooting the host).
This is all because...
...it [docker 0.9] contains a new "engine driver" abstraction to make possible the use
of other API than LXC to start containers. It also provide a new
engine driver based on a new API library (libcontainer) which is able
to handle Control Groups without using LXC tools. The main issue is
that if you are relying on lxc-attach to perform actions on your
container, like starting a shell inside the container, which is
insanely useful for developpment environment...
source
Please note that this will prevent the new host only networking optional feature of docker 0.11 from "working" and you will only see the loopback interface. bug report
It turns out that the solution to a different question was also the solution to this one:
...you can use docker ps -notrunc
to get the full lxc container ID and
then use lxc-attach -n <container_id>
run bash in that container as
root.
Update: You will soon need to use ps --no-trunc
instead of ps -notrunc
which is being deprecated.
Find the full container ID
Enter the lxc attach command.
Top shows my apache process running that docker started.