If Docker is about packaging, then it's one of the worst package management systems I've ever used. I use Docker for the abstraction over namespaces and cgroups mainly, and get frustrated with the layers of disk images, bad caching system, poor security story, and the weak Dockerfile DSL.
Perhaps the parent poster was wryly indicating that he doesn't think that much of Docker. Certainly I think both of you are correct: Docker is about packaging, and it absolutely sucks at that. The only reason that that is not obvious is that Docker is piggybacking on the relatively excellent and well-developed package management of distributions like Debian and Fedora.
Debian and Fedora do packaging better than Docker, relatively speaking, but they still have major issues that have lead to "solutions" like Docker, Chef/Omnibus, etc. They install packages globally which doesn't allow for having multiple versions of the same software/library, they don't allow for unprivileged package management so users are at the mercy of the sysadmin, there's no transactional upgrades and rollbacks for package updates gone bad, and builds aren't reproducible (Debian is doing great work to fix this, though), to name the most important issues.
I work on the GNU Guix project, which can do all of these things. Additionally, with Guix, I have access to a configuration management system that can create disk images, VMs, and (in a future release) containers (replace Chef/Puppet/Docker), a tool for quickly creating isolated dev environments without polluting the rest of the system (replaces virtualenv and Vagrant when combined with a VM/container), and more.
I'm convinced that more featureful package managers can and will solve a lot of our software deployment problems, and I'm also convinced that simply layering more tools on top of a shaky foundation isn't going to work well in the long term.
> Debian and Fedora do packaging better than Docker, relatively speaking, but they still have major issues that have lead to "solutions" like Docker, Chef/Omnibus, etc.
I get what you're saying, but the way you've phrased it makes it seem like it wasn't intentional when in fact before immutable git-style packages were discovered, you were forced to choose between packaging that works well for developers/ops and packaging that works well for end users.
Debian is the best example we have of the latter, but it's a mistake to say they did a bad job at making ops-friendly packaging. They are solving a different, mutually-exclusive (until recently) problem.
With a bunch more elbow grease and polish, the nix/guix approach allows us to have the best of both worlds, but this is a very new development; arguably it isn't even "there" yet.
Debian and Fedora do it better, yes. But it's not quite as easy to get started.
However once you are at a certain size, both solutions are horrible. (Docker and RPM).
Especially when you need to target more than one Fedora / CentOS / RHEL / etc...
Also editing Spec files is quite horrible.
>The only reason that that is not obvious is that Docker is piggybacking on the relatively excellent and well-developed package management of distributions like Debian and Fedora.
s/well-developed/widely-used
Just because a package manager has a broad user base does not make it excellent nor well-developed. pacman[1] user base is far smaller, but (IMHO) it's a much more refined package manager than apt or rpm.
