-Since the default change in debootstrap 1.0.102, some issues have arisen. Due to the fact that some buster/sid hosts have the "merged `/usr`" symlinks in place, it has been observed that some binary packages carried some traces of these differences (notably official packages built on Debian buildd hosts which had been resetup). Some such differences can actually render the built packages unuseable on non-"merged `/usr`" systems. For example, if `cat` is detected at build-time in `/usr/bin/cat` (where coreutils ships `/bin/cat`), a binary hardcoding that path will try to use `/usr/bin/cat` after installation, but that path doesn't exist in non-"merged `/usr`" systems. In order to mitigate this, debootstrap has been modified to let its "buildd" variant be non-"merged `/usr`", the Debian buildds have been resetup and the affected packages rebuilt.
+## Issues from "merged `/usr`"
+
+Since the default change in debootstrap 1.0.102, some issues have arisen.
+Due to the fact that some buster/sid hosts have the "merged `/usr`" symlinks in place, it has been observed that some binary packages carried some traces of these differences (notably official packages built on Debian buildd hosts which had been resetup).
+Some such differences can actually render the built packages unuseable on non-"merged `/usr`" systems.
+For example, if `cat` is detected at build-time in `/usr/bin/cat` (where coreutils ships `/bin/cat`), a binary hardcoding that path will try to use `/usr/bin/cat` after installation, but that path doesn't exist in non-"merged `/usr`" systems.
+In order to mitigate this, debootstrap has been modified to let its "buildd" variant be non-"merged `/usr`", the Debian buildds have been resetup and the affected packages rebuilt.
+
+The lesson here is that with the existance of (any of) the usrmerge and the debootstrap default change, "merged `/usr`" Debian systems exist already, and that packages built on hosts with such directory schemes can _potentially_ be broken on non-"merged `/usr`" systems.
+At this point, the two variants have to be supported, at least as installation targets of Debian packages.
+
+Two initiatives are worth mentioning at this point:
+* [a patch](https://lists.debian.org/20181202212535.GC11687@gaara.hadrons.org) has been proposed for dpkg-buildpackage to mark packages built on "merged `/usr`" hosts with a `Build-Tainted-By: merged-usr-via-symlinks`;
+* the reproducible builds team has added a "merged `/usr`" variation to their setup, and have then [tagged](https://tests.reproducible-builds.org/debian/issues/unstable/paths_vary_due_to_usrmerge_issue.html) the Debian packages from unstable which had differences due to "merged `/usr`". It seems that ~61 packages were affected by differing builds; 32 from these have been fixed in unstable already.
+
+## The long-term desireable situation
+
+Various valid long-term desireable situations coexist, and while discussing immediate countermeasures, it is useful to keep the long-term outcome that those are most likely to produce.
+
+These are the six possible situations at the time of bullseye (buster + 1):