Hi Josh, On Sat, Jan 04, 2025 at 10:10:26AM +0200, Josh Triplett wrote: > Helmut Grohne wrote: > > As far as I understand it, we may pick any three: > > * Allow systemd to manage /lib64 as it does. > > * /usr-move > > * Multiarch > > * Multilib > > By "/usr-move", do you mean the overall /usr migration, or do you mean > the idea of linking /lib64 to /usr/lib64 unconditionally (e.g. in > base-files)? The latter seems like a viable solution, and a *useful* one > for multiarch. If someone is on arm64 (without /lib64), and they want to > have amd64 libraries installed, *something* needs to be responsible for > installing a /lib64 symlink to /usr/lib64, and base-files seems like the > obvious candidate to do so. That would avoid having to have any special > logic in packages that need /lib64. The only cost would be having an > "unnecessary" symlink on targets like arm64 (which stops being > unnecessary as soon as the system installs multiarch packages from a > target that needs /lib64).
I would say that the answer is more nuanced. When I say /usr-move, what I mean is emptying directories such as /bin, /lib and /sbin but also /lib64 and moving all of their files to the corresponding /usr location as a mechanism to avoid aliasing effects from surfacing in dpkg. As such, /usr-move is an extension of /usr-merge, which merely says that /bin, /lib, /sbin and a few more are symbolic links. (Let's forget about the alternative merge via symlink farms for now.) The implication of /usr-move is that libc6:amd64 installs /usr/lib64/ld-linux-x86-64.so.2 rather than /lib64/ld-linux-x86-64.so.2 and expects /lib64 to always exist. Your suggestion of having these links managed by base-files is already implemented. In trixie and later, base-files installs /bin, /lib, /sbin as symlinks via its data.tar. On amd64, it also installs /lib64 that way, but not on arm64. (Please consider these equivalence classes with an eye towards Simon's mail.) If you install libc6:amd64 on an arm64 installation, it will unpack /usr/lib64. This unpack happens to activate a base-files trigger and base-files will subsequently create the /lib64 symlink. I think we already are where you want us to be as you may practically assume /lib64 to exist whenever any package installs anything into /usr/lib64. Unconditionally installing an empty /usr/lib64 (and /lib64) for all architectures is something that would technically work indeed. Once /usr/lib64 exists everywhere, the logic in systemd will never create a /lib64 -> usr/lib symbolic link and the dispute is resolved. I happen to disagree with this being a good solution, but the CTTE may overrule me here. Helmut
