Yeah, typically, but in this case they're commiting and commiting in the container image, and saving changes from running software. Not only that, they're commiting log files into the image, which is crazy.

The thing here is they're using Docker container images like if they were VM disks and they end up with images with almost 300 layers, like in this case. I think LXC or VMs should be a better case for this (but I don't know if they've tested it or why are they using Docker)