Lines of code is irrelevant.

Docker is important because:

1) it made a convenient process to build a “system” image of sorts, upload it, download it, and run it.

2) (the important bit!) Enough people adopted this process for it to become basically a standard

Before Docker, it wasnt uncommon to ship some complicated apps in VMs. Packaging those was downright awful with all of the bespoke scripting needed for the various steps of distribution. And then you get a new job? Time to learn a brand new process.

I guess Docker has been around long enough now that people have forgotten just how much of an absolute pain it used to end up being. Just how often I'd have to repeat the joke Them: "Well, it works on my machine!" Me: "Great, back up your email, we're putting your laptop in production..."

The other half is the other 90%.

Looking at it now, it won't even run in the latest systemd, which now refuses to boot with cgroups v1. Good luck even accessing /dev/null under cgroups v2 with systemd.

And like the famous hacker news comment goes, Dropbox is trivial by just using FTP, curlftpfs and SVN. Docker might have many faults, but for anybody that dealt with the problems that it aimed to solve do know in that it was revolutionary in simplifying things.

And for people that disagree, please write a library like TestContainers using cobbled together bash scripts, that can download and cleanly execute and then clean up almost any common use backend dependency.