Understanding the bin, sbin, usr/bin , usr/sbin split

Today on twitter I asked the question, “How did we ever come by the convention of /usr/local/bin/ ? That folder is not there by default but most *nix heads put all our apps there.”

And this link was the answer I got.

“You know how Ken Thompson and Dennis Ritchie created Unix on a PDP-7 in 1969? Well around 1971 they upgraded to a PDP-11 with a pair of RK05 disk packs 1.5 megabytes each for storage.When the operating system grew too big to fit on the first RK05 disk pack their root filesystem they let it leak into the second one, which is where all the user home directories lived which is why the mount was called /usr. They replicated all the OS directories under there /bin, /sbin, /lib, /tmp… and wrote files to those new directories because their original disk was out of space. When they got a third disk, they mounted it on /home and relocated all the user directories to there so the OS could consume all the space on both disks and grow to THREE WHOLE MEGABYTES ooooh!.–via Understanding the bin, sbin, usr/bin , usr/sbin split.