[kakwa_]

I think docker succeeded not because it was a better container or virtualization solution, or because it was lighter than VMs. Jails or Solaris zones have existed for years or decades, and on Linux, we had openvz and vserver long before Docker. And I'm not even mentioning plain old chroot (with indeed some security issues).

I didn't follow the latest development, but for a while, Docker was not even that great in term of robustness and stability. I never was a big fan of the userland proxy for example. And from what I've read, upgrading from one docker version to another could be quite painful (disclaimer: I toyed with docker a little, I haven't used it in production yet).

IMHO, Docker succeeded because it brought a complete ecosystem around containers:

* Ways to generate the container image through Dockerfile

* Ways to compose an image on top of another (itself on top of another, etc...)

* Ways to share and distribute these images with Docker Registry