// Remove from oldest to newest (last to first).
	numToKeep := len(containers) - toRemove
	if numToKeep > 0 {
		sort.Sort(byCreated(containers))
	}
	for i := len(containers) - 1; i >= numToKeep; i-- {
		if containers[i].unknown {
			// Containers in known state could be running, we should try
			// to stop it before removal.