Comment by nobody9999
4 years ago
>the original separation of / and /usr happened for intensely silly reasons
As I recall, there were very good reasons for separating / and /usr (as well as /home and /var). The biggest one was that various Unix kernels would panic[0] if / was full. But that issue was almost universally fixed by 1990 or so.
And netmounts of pretty much everything other than / were pretty common for many years, due to the high cost of storage.
So no, the reasons weren't silly, they just don't apply to more modern systems.
OK, I didn’t put this completely correctly. The original separation of /usr to hold user home directories (!) and / to hold everything else was because the first RK05 disk ran out, but it makes sense in any case. The additional hierarchy under /usr was created some time later when space on the first RK05 disk ran out again, and while this can be a perfectly sensible decision for a single installation on a single site, taking it seriously decades later is silly. Neither does that mean that there weren’t good reasons the split got preserved in subsequent systems, just that they couldn’t have been the same as the original ones; there are no netmounts in V6, after all.
(I have an old Unix intro book that describes /usr as user home directories, the rest is a second-hand retelling[1].)
[1] http://lists.busybox.net/pipermail/busybox/2010-December/074...
Interesting stuff. Thanks for sharing it!