As a way to improve my understanding of the issue at hand, here's my current
collection of data points regarding the "merged-/usr" question:
* "merged-/usr" was enabled by default in debootstrap on June 13. 2018, some
5+ months ago. Any buster rootfs setup since has the /bin → /usr/bin
symlink (and other caracteristics of merged-/usr).
https://tracker.debian.org/news/965045/accepted-debootstrap-10102-source-all-into-unstable/
* With my TC hat on, I have formally asked the debootstrap maintainers
(and specifically Hideki Yamane) if they would consider a toggle of the
default.
https://bugs.debian.org/914897#73
* a discussion "usrmerge -- plan B?" was started on Nov. 20 on debian-
devel@l.d.o
https://lists.debian.org/20181120211617.gxnuwxpx2hy445ps@angband.pl
It apparently follows #913229, #914204 and others.
* Currently, according to my `apt-file`, 259 binaries are shipped in /bin
directly, accross 85 packages. (for /sbin, 597 binaries for 190 packages).
* There exists a 'usrmerge' package since 2015, which transforms a rootfs with
separate /{bin,sbin,lib} into a "merged-usr/" rootfs. It has had 28 bugs
over its lifetime; of which 4 are currently open. After successful
"installation" (when the postinst successfully ran the
/usr/lib/convert-usrmerge program), /{bin,sbin,lib} are made symlinks and
the package can be removed. The package doesn't include a way to revert the
rootfs to its previous state.
* Building source packages in a merged-/usr rootfs can make the resulting
binary packages broken in non-merged-/usr rootfs'es, because they'd be
embedding references to /usr/bin/grep (e.g.), which don't exist in non-
merged-/usr rootfs'es. To ensure this doesn't happen for packages built on
Debian infrastructure, debootstrap has been updated to disable merged-/usr
for the `buildd` variant (and buildd chroots have been rebuilt).
* According to investigation done thanks to reproducible builds (which now
also varies the merged-/usr state of the build rootfs), and by others,
packages affected by this problem have begun receiving either
reproducibility issue tags or Debian bugs:
https://tests.reproducible-builds.org/debian/issues/unstable/paths_vary_due_to_usrmerge_issue.html
(currently: 59)
https://bugs.debian.org/cgi-bin/pkgreport.cgi?users=md@linux.it;tag=usrmerge
(current total: 81; outstanding: 17)
I'll post my thoughts separately; please enhance or correct the above data
as needed!
Cheers,
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