Ken Moffat wrote:
On Mon, Aug 24, 2015 at 06:50:32PM +0200, Simon Kitching wrote:
Hi All,
I've just finished working through the LFS book, and am now in the middle of
BLFS. Thank you all for both books - they are extremely well written.
I do have a few questions/comments, and I'll start with probably the most
controversial one first. Please note, however, that I'm just politely
asking, and am not trying to push any point of view on anyone :-)
Have you considered using the unified-usr approach in LFS (as used by Fedora
17+)? See:
* http://www.freedesktop.org/wiki/Software/systemd/TheCaseForTheUsrMerge
* http://fedoraproject.org/wiki/Features/UsrMove
If so, is there a wiki page (or similar) anywhere which discusses your
conclusions?
Thanks & Regards,
Simon
We (still (claim to)) support people who mount /usr as a separate
filesystem - perhaps as an nfs mount shared across multiple
machines. Not a common configuration, and I think nobody is
actively testing it, but not something we have any desire to
invalidate in the main (sysvinit) books.
For building in a single largeish fileysystem, there is minimal
extra work in putting things into /lib or /bin, /sbin so the
unified-usr approach does not appear to offer any significant
benefits.
We really need to look at Unix history to understand *why* we had
/usr/{bin/sbin/lib} at all.
At one time disk drives were very small and expensive. Creating the
split was an economic issue. On today's systems, that's not needed:
$ du -sh /bin /sbin /lib /usr
5.3M /bin
16M /sbin
28M /lib
5.2G /usr
That said, there is no good reason to undo the split. The above link
says "Maintaining the /usr split requires non-trivial project-specific
handling in the upstream build system, and in your distribution's
packages." I do not agree that the handling is non-trivial. It's true
that we at times move some binaries and libraries from /usr/bin and
/usr/lib to /bin and /lib, but that's really pretty easy and not that
frequent.
Really the only packages needed in /bin or /sbin is those needed to get
the system running enough to mount /usr. In the simple case, that's
just a mount command. In more complex cases networking must be started
and NFS or equivalent set up. It can also get more complicated when
partitions are encrypted.
If distros like RedHat were really looking for consistency, they would
use /bin, /lib, and /sbin, and remove them from /usr. What they really
are doing is trying to make things easier for themselves by not being
concerned where each package file is placed. To the user, it makes no
difference today.
-- Bruce
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