Logentries Docker container will not start

I have just added the Logentries Docker container, to a Rancher setup. We have another set of LE Docker containers running already just fine. However, this new container will not start – the logs say:

events.js:85
  throw er; // Unhandled 'error' event
Error: connect ENOENT
  at exports._errnoException (util.js:746:11)
  at PipeConnectWrap.afterConnect [as oncomplete] (net.js:1012:19)

I am not familiar enough with Logentries' Docker-based setup to understand what is going on here.

It looks like it is failing to connect to something, but what? How can I try to find out?

So the problem is linking docker.sock into the Logentries containers.

Logentries' documentation says you'll need a docker command something like this:

docker run -v /var/run/docker.sock:/var/run/docker.sock logentries/docker-logentries -t <token>

But in Rancher you don't enter the raw Docker command, you have to attach the volume when creating the service, equivalent to the -v /var... option in the docker command.