sbin is a SYSVR4'ism ... it's complicated. /etc had a bunch of binaries in it like fsck. MACH systems had that as well (well technically it was linked to /priva

sbin is a SYSVR4'ism ... it's complicated. /etc had a bunch of binaries in it like fsck. MACH systems had that as well (well technically it was linked to /private/etc which then linked the binaries to /usr/etc - here's an openstep screenshot I just took: http://9ol.es/usr-etc.png http://9ol.es/usr-etc.png). It's /etc/mkfs /etc/route ... they got moved to /usr/sbin/ and /sbin in R4 - by then, SYSV systems were using /home and the initial purity of every owner of every process being an equivalent class user had been broken by pragmatism. The invention of /sbin/ /usr/sbin is all R4, see https://archive.org/details/unixsystemvrelea0000unse_t8i3/page/n1071/mode/2up https://archive.org/details/unixsystemvrelea0000unse_t8i3/pa... Unix 1980s history is a complicated mess ... that's why there were multiple conflicting standards groups that tried to fix it. The X/Open group had the "single unix specification" which is different from POSIX and say, the Open software foundation (which did OSF/1). Here's a nice crash course: https://en.wikipedia.org/wiki/Single_UNIX_Specification https://en.wikipedia.org/wiki/Single_UNIX_Specification Explaining the history with the motivations is probably around 10,000 words. AFAIK it hasn't been written. I'd be one of the handful of wackos who'd actually do that and I haven't seen it.