On Tue, Jul 21, 2020 at 11:56 AM Grant Taylor via TUHS <tuhs@minnie.tuhs.org> wrote:
One of the things that I've noticed in my explorations into the H.J. Lu
bootable root disks is that some of them predate the /sbin split in Linux.

One of them has exactly one file in /sbin and other commands spread
across /bin, /usr/bin, and /etc.  The single file in /sbin is sln.

To me, this makes it fairly self evident that /sbin was originally for
statically linked binaries.  At least in Linux.

The root disks date from a time before Linux had shared libraries, I thought, though I've not looked at HJ Lu's disks in a very, very long time. And I stopped looking very early on once I had my system bootstrapped... I do recall going through some pain to bootstrap shared libraries on my system...
Does anyone have any history of /sbin from other traditional Unixes?
I'd be quite interested in learning more.

/sbin has never been for static binaries in BSD land. It's always for system admin binaries that used to live in /etc. They moved to /sbin or /usr/sbin. This split is due to historically tiny / filesystems and the need to have just enough binaries on them to check and mount /usr later in boot. It dates from 4.3-RENO. There were no shared libraries in BSD at the time (though I think contemporaneous Sun systems had them, which is where Linux got its first a.out shared library scheme from (kinda, sorta, more inspired by with some code snatched from gcc/binutils SunOS compat impl, but with more limitations)).
I also noticed that (at least) one of the early versions of the H.J. Lu
disks had root's home directory in /usr/root.

I seem to recall that one version used an atypical of /users vs /usr.
Which as I understand it, goes back to the original / vs /usr split in
Unix, before /home became a thing.

Early days this was actually quite common. You put your users under /usr/foo because there weren't many of them, and you'd save a inode lookup over /usr/users/foo and you didn't need a separate filesystem for your users. I saw it more on 'small' systems with limited number of users rather than big, university systems with student populations on them (which needed a separate filesystem to hold all the user content, even with draconian quota limits).

Grant. . . .
unix || die