The Filesystem Hierarchy Standard [0] has been around for ~25 years but it still took quite a long time before most Linux distros decided to adhere to it (for the most part; some still do "non-standard" things at times).
Now that we're to that point, please stop screwing it up and coming up wih your own locations for application binaries, data, etc.
To be clear, the "/data" directory -- under which Moloch's pre-built packages apparently install to, according to the README [1] -- is not part of the FHS.
If the use of /data is the reason why you're not using this software, I'm pretty sure you wouldn't find any use of it if it stored data someplace in /var either.
Personally, I think the FHS is stupid marketing wankery that barely made sense in 1995 when the "preciousness" of the root partition was relevant, and has in the annals of time, caused more problems than it ever could have solved. Hey, what's the path to python? Is it:
This is perhaps the only question I need a "standard" to solve, and I've given up[†]. I don't need to know mail is "sometimes" in /var and sometimes in /var/local. I don't need to know that some of my configuration files are in /etc and others are in /usr/local/etc whilst still others are in /lib someplace. Where are my libraries? maybe /lib, /usr/lib /usr/local/lib /usr/lib64 /usr/local/lib64 and who knows where else. Fuck it, I'll just use find /.
I saw this great quote recently -- I know it was about something else, but I still wish Dan and the other FSSTND/FHS people could have seen and understood it all those years ago:
I suppose people blindly following suggestions on the Internet will eventually learn a hard lesson -- don't.
Because that is what the FHS was: A bunch of suggestions on a mailing list, with a smattering of armchair philosophy lacking any real analysis. But I mean, that's just my opinion. What if I'm wrong? ¯\_(ツ)_/¯
[†]: The answer is whatever /usr/bin/env python says.
If you look at the source code of most open source software, the devs typically install by default to arbitrary directories. They either don't know about, or care about, operating system standards. When Linux distributions package that software, they choose to change how that software works to align with standards. Usually their own standards, but those can often align with distro-independent standards too. But as a packager, you expect that you'll be modifying paths and making patches.
So really it doesn't matter where a random dev decides to install their software to by default, since either A) it's proprietary and it's non-standard anyway, or B) it's up to us to package it the way we want it.
Not everyone is using a package manager for every install, and even then it's not a magic bullet. I'm a Mac user and I've no idea why devs insist on installing to places like /usr/local or putting configuration in a dot file in my home directory when there's a standard place to put those (~/Library/Application Support), among other well thought out directory structuring[1].
Further to this, the moment you want to install somewhere else or have a dependency elsewhere (e.g. /opt/anything) builds break because of hard coded paths and poor assumptions. To top it all, I've no idea why a package manager like Homebrew then contributes to all of this by acting like no of this matters because a Mac is just like Linux, apparently.
If they don't like Apple's way then why not XDG[2]? Reinventing the wheel badly is more than just hubris, it breaks things and it's annoying.
This post 'gonna cost me, but what you write is endogenous to the FHS making little sense to most people who don't have a unix background.
"Where ARE my programs / settings that I installed, I always have to google it!"
is interrelated with someone else asking
"Where should I PUT this program / setting / data? I guess I'll chose one of those three or so locations where it may fit, or several"
For example: Why isn't there a data directory to be found? Where does the data go?
Why not replace nondescript and unhelpful names like "opt" and "usr" (which is btw. not where the user data is!)?
/usr is absolutely where user data was. That's what it stands for "users".
First when / ran out of space, new programs were put on the other disk /usr in /usr/bin so everyone could assume programs were in /bin except ones that were newly installed so they would be in /usr/bin
When /usr ran out of space, a new disk was added as /home and things that were easier to move (user directories) were moved first leaving things that everyone's script was depending on (#!/usr/bin...) where they were.
This was done out of necessity, not out of good taste.
In the original Unix implementations, /usr was where the home directories of the users were placed (that is to say, /usr/someone was then the directory now known as /home/someone).
It still had /usr/bin and /usr/sbin in it and scripts, muscle memory and general inertia to contend with. Yes of course it should have gone away, perl should have been at v6 and python at v3 years ago.
I'm off to saddle up my piggie squadron for a flypast.
Now that we're to that point, please stop screwing it up and coming up wih your own locations for application binaries, data, etc.
To be clear, the "/data" directory -- under which Moloch's pre-built packages apparently install to, according to the README [1] -- is not part of the FHS.
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[0]: https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard
[1]: https://raw.githubusercontent.com/aol/moloch/master/release/...