I'm reading this document about the move towards merging /bin into /usr/bin:
The historical justification for a /bin, /sbin and /lib separate from /usr no longer applies today. (More on the historical justification for the split, by Rob Landley) They were split off to have selected tools on a faster hard disk (which was small, because it was more expensive) and to contain all the tools necessary to mount the slower /usr partition. Today, a separate /usr partition already must be mounted by the initramfs during early boot, thus making the justification for a split-off moot. In addition a lot of tools in /bin and /sbin in the status quo already lost the ability to run without a pre-mounted /usr. There is no valid reason anymore to have the operating system spread over multiple hierarchies, it lost its purpose.
but if I understand this correctly, the reasonable course of action for removing the root-vs-/usr split is to just merge all of /usr "back" into the root folder, i.e. have /bin, /share, /local, a merged lib/ and so on.
Why merge in the other direction, maintaining an artificial path element which no longer makes sense?
/bin//lib//shareis not the one that is relevant now. The relevant distinction is now read-only vs writable. There's/usrthat's supposed to be read-only except for package updates, there's/varfor writeable part. – muru Apr 06 '22 at 16:20/bin(available early, on a fast small disk) is no longer a requirement./binshould go away, but old programs and scripts should not be broken. – waltinator Apr 06 '22 at 16:24/varin an otherwise non-writeable root filesystem - with a mount. – einpoklum Apr 06 '22 at 16:32/var. Having a writable/varisn't the point. Having all your readonly stuff nicely sequestered in corner of the filesystem (/usr) is. Then/usrat any given point in time represents (to a degree) a set of packages each at some given version. Upgrading, adding, removing or any other package manipulation then is essentially swapping sets of/usraround. You can't swap around something when you have a mounted writable directory in it, so having all your readonly stuff spread all across/is useless for this world-view. – muru Apr 06 '22 at 18:07/etc,/usr/local, etc., but/etccan be worked around to a degree and the people who're interested in these operations aren't those who will be using/usr/local. – muru Apr 06 '22 at 18:08/usrwould not represent a set of packages, since packages include files outside of/usr, and files which can and do get altered. You're trying to argue on the basis of a world which doesn't exist and the merge is supposed to comply with. – einpoklum Apr 06 '22 at 19:29/usraspect of it. 2. Yes, thank you for restating my last comment. But/usrdoes represent the vast majority of those files, and for many packages, all of them. – muru Apr 07 '22 at 00:37