Occasionally dind fails to start: "sed: write error" about docker HOT 2 OPEN

Oh, your case is slightly different from the one I commented in #308 (comment) -- in your case, I think it might actually be your docker exec that's causing the problem (since you're creating processes while the script is still trying to initialize and thus exacerbating the inherent race between the lines of the dind script trying to set up the cgroup appropriately).

from docker.

What I might suggest instead is putting /run in a shared volume and using docker run for your docker info checks instead of docker exec (connecting to the socket from a second container instead of going into the first).

from docker.