Modularity, compartmentalization, reliability, predictability.

One software needs MySQL 5, another needs mariadb 7. A third service needs PHP 7 while the distro supported version is 8. A fourth service uses cuda 11.7 - not 11.8 which is what everything in your package manager uses. a fifth service’s install was only tested on latest Ubuntu, and now you need to figure out what rpm gives the exact library it expects. A sixth service expects odbc to be set up in a very specific way, but handwaves it in the installation docs. A seventh program expects a symlink at a specific place that is on the desktop version of the distro, but not the server version.

And so on and so forth… with docker not only is all this specified in excruciating details, it’s also the exact same setup on every install.

You don’t have it not working on arch because the maintainer of a library there decided to inline a patch that supposedly doesn’t change anything, but somehow causes the program to segfault.

I can develop a service on windows, test it, deploy it to my Kubernetes cluster, and I don’t even have to worry about which machine to deploy it on, it just runs it on a machine. Probably an Ubuntu machine, but maybe on that Gentoo node instead. And if my osx friend wants to try it out, then no problem. I can just give him a command, and it’s running on his laptop.

If you’re an old Linux admin… This is what utopia looks like.