I'll put it in context.

Let's say I have leftover garbage in usr/local/lib. I clone a new project that I need to patch because it's broken. I try to fix the new project but the fix isn't working. I have no idea why. I spend hours trying to trace down the problem.

What was the issue? The project picked up some of the old garbage libraries I had in usr/local/lib, which had a bug that made my fix not work.

For developers, global dev library garbage = global mutable state. It interferes with development, creates more sources of potential issues, and takes time to trace and debug. A clean and/or localized environment is essential for the accurate pinpointing of bugs and issues.

> I spend hours trying to trace down the problem.

This is the problem. Once you understand library loading, once on your system, and learn, once, how to query the system and see what libraries are being loaded and from where, you won't have to waste hours on this problem again. Until that point, you're operating a system without understanding, and that will always lead to breakage.

I've installed hundreds of pieces of software from source, and I have a fairly decent idea of how linking and loading works. I still have to spend time figuring out why something doesn't build when it should due to something strange about my system.

Of course I understand how it works. I just can't constantly keep in mind what garbage I played around with 3 months ago that might be responsible for the issue I'm looking at right now. I don't expect it, and more importantly, I shouldn't have to expect it.

It's a basic tenant of development. Eliminate all additional sources of issues and complexity by presenting a clean, well-controlled sandbox in order to effectively diagnose it and fix the real bug.

In fact, you should be able to try a newer version of a dependency, an older one, or run 10 variants (containers) each with different versions to e.g. test whether the project you're working on is widely compatible with a flexible range of that dependency. These things are done all the time.

The tools are inadequate, not the developers. Engineers on both sides need to stop assuming everyone else is an idiot.

As someone who’s spent a lot of time as a sysadmin over the years, your last comment sounds backwards to me. The DevOps trend has pushed more general awareness and Docker has played a key role in three ways: making explicit automation requirements for the setup process (Dockerfiles have to work, unlike that MS Word document someone last updated 3 years ago), being private by default and requiring someone to reverse engineer the system to learn which things should be shared, and being immutable means that teams are forced to document shared state and backups rather than leaving messes behind for ops to deal with.

The key to understanding the benefit is the power of having done this in a standard, widely used way which is supported by many tools, used by an increasing fraction of projects, and which makes knowledge and training broadly portable. Some shops had some of those benefits but most fell short in multiple areas, ran into arguments with vendors / contractors, or required substantial ramp-up time for anyone new. Distribution packaging solves some problems very well - there’s a reason almost everyone uses it inside containers - but it has well-known problems with conflict resolution and coordination which are not easy to solve, tending to lead to inflexible policies and restrictions. Having a standard answer for the boundaries between generic system-level and application-specific concerns has been a great way to improve both sides while saving a good deal of time.

> The key to understanding the benefit is the power of having done this in a standard, widely used way which is supported by many tools, used by an increasing fraction of projects, and which makes knowledge and training broadly portable.

You're talking about Makefiles here circa 25 years ago, right?

Makefiles have to work, and /bin/sh is still there last I checked on my machine. The problem with the broadly portable knowledge and training is that many people seem to think "don't bother with all that, just use docker" is an acceptable answer and "best practice" is not to learn Unix because it's not new and shiny.

Saying makefiles solve that is like saying screws solved construction. They partially address only one of the concerns I mentioned, doing nothing for the others, and as the numerous tools in that space (automake, cmake, etc.) show they’re hardly a complete solution even for just the challenge of building things.

> Makefiles have to work

And yet I get GNU Makefiles all the time that don't work when I type "make" at my computer, since they use things that aren't compatible with my version of Make. It's clearly more of a problem than you think it is.