On Thu, Dec 20, 2012 at 2:42 AM, Volker Armin Hemmann <volkerar...@googlemail.com> wrote: > with redhat's push to move everything into /usr - why not stop right there and > move everything back into /?
I originally thought this way, but they actually reviewed the technical and historical merits for all the use cases and and found /usr to be superior. Straight out of the freedesktop wiki: http://www.freedesktop.org/wiki/Software/systemd/TheCaseForTheUsrMerge 0) If / and /usr are kept separate, programs in /usr can't be updated independently of programs in /, because the libraries they depend on might break compatibility. If the binaries and libraries were *all* in /usr, then the entire system's binaries would always be consistent regardless of where /usr were sourced from (config files in /etc, however, would still break). 1) There is historical precedent in Unix for /usr-centric systems, notably Solaris. 2) If /usr were separated from /, then /usr could be mounted read-only, with / being mounted "normally". Which makes sense, as / does have bits that are meant to be read-write. 3) Most software packagers write their binaries to a PREFIX defaulting to /usr/local, or /usr, as opposed to /. Determining which ones belong in / or /usr can sometimes be dependent on the distro and/or sysad. But since more of them default to /usr, if everything were in /usr it'd be a saner default. (0) basically says that keeping them separate only works as intended if the both the sysad and the distro upstream work together for their shared /usr mount. In many cases, however, sysads have to do a lot of working around and careful planning to get /usr mounted remotely. (1), (2), and (3) provide advantages to mounting the binaries and libraries separately from the / filesystem, which mounting them as part of / does not provide.
