Re: [gentoo-user] Re: Anyone switched to eudev yet?

[Mark David Dumlao]

On Thu, Dec 20, 2012 at 2:42 AM, Volker Armin Hemmann
<volkerarmin@××××××××××.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.