Comment 4 for bug 1420640

I figured out our problem. We lowered `fs.nr_open` on the non-working systems from the - apparent default - of `1048576` to `655360`. The docker package set a limit higher than our new limit, so the process was failing to start.

Upstart is going away - boo - but in case anyone sees this issue in the future, running the following was the fix for me:

```
sysctl -w fs.nr_open=1048576
```