>> For the benefit of Linux newcomers like me, could someone explain the >> historical reasons why we even have a /usr/local directory to begin >> with? > > Because in many environments /usr is NFS-shared across a lot of >machines.
it goes back before NFS. the original *nix backup utilities (dump/restore) worked at the filesystem level. it was much easier as a sysadmin to have backups of /, /usr and /usr/local so that if you did a system upgrade or reinstall, you simply installed the OS on / and /usr, then did a full restore of /usr/local, and you'd instantly get all the site-installed stuff back. if you didn't do this, system upgrades/reinstalls could get nightmarish very quickly (and they weren't easy to begin with). NFS just reinforced the usefulness of this approach. later, solaris introduced the idea of /opt for the local stuff, but it never really took off in any other *nix systems AFAIK. you might be wondering why we have / and /usr ... this so that the system can boot with just a single filesystem, then come up to a multiuser state by mounting /usr. putting them in different filesystems lets you allocate space and administrative controls more easily. /usr tends to be fairly static in size, and / tends to have log files and other stuff that grow and are resized fairly often. --p (once known as <[EMAIL PROTECTED]>)
