merged usr: Remove `full` from consideration

Platform ABIs require /lib and /lib64 to exist, and widespread
assumptions require /bin and /sbin, so there's little point in trying
to remove them altogether. I am not aware of any distributions that
have considered removing the symlinks, even those where merged /usr was
a mandatory flag-day transition.

Acked by OdyX on IRC.

diff --git a/914897_merged_usr/ballot.md b/914897_merged_usr/ballot.md
index 6f63671db969274d5bd4d5e90931651daffb1478..949b2f40e6b1a1fec6c3b0ffc7885290213a8e9f 100644 (file)
--- a/914897_merged_usr/ballot.md
+++ b/914897_merged_usr/ballot.md
@@ -4,7 +4,7 @@
 
 ## What is "merged `/usr`"
 
-"Merged `/usr`" describes a possible future standard directories scheme in which the `/{bin,sbin,lib}/` directories have been made superfluous, either through replacing them by symlinks to their `/usr` equivalents (/usr/{bin,sbin,lib}) or by removing them entirely.
+"Merged `/usr`" describes a possible future standard directories scheme in which the `/{bin,sbin,lib}/` directories have been made superfluous through replacing them by symlinks to their `/usr` equivalents (/usr/{bin,sbin,lib}).
 The motivation to get Debian systems to converge towards such a scheme is vastly documented elsewhere ([FDO's TheCaseForTheUsrMerge][0], [wiki.d.o UsrMerge][1]) but can be summarized as the following points:
 
 * having separate `/` and `/usr` filesystems has been useful in the past for booting without initramfs onto a minimal root filesystem that carried just enough to mount the `/usr` filesystem later in the boot process. Given the evolution of physical hosts' capabilities, initramfs'es have been default in Debian (and elsewhere) for a long time, and most systems no longer have an intermediate state during boot in which they have only `/`, but not `/usr`, mounted.
@@ -22,6 +22,8 @@ The arguments against moving the base directories' scheme towards "merged `/usr`
 [0]: https://www.freedesktop.org/wiki/Software/systemd/TheCaseForTheUsrMerge/
 [1]: https://wiki.debian.org/UsrMerge
 
+The compatibility symbolic links `/lib` → `/usr/lib` and `/lib64` → `/usr/lib64` are required by the various CPUs' platform ABIs (for example i386 requires `/lib/ld-linux.so.2` to resolve to glibc's `ld.so`, and amd64 requires `/lib64/ld-linux-x86-64.so.2`) so there are no plans to remove them altogether. Similarly, removing `/bin` is not under consideration because it would break the assumption that `/bin/sh` exists, and removing `/sbin` would break the assumption that `/sbin/fsck.*` and `/sbin/mount.*` exist.
+
 ## "merged `/usr`" in Debian
 
 In Debian buster, the current testing suite, "merged `/usr`" is only considered for implementation with symlinks (there are no proposals for simply dropping `/{bin,sbin,lib}`) and is implemented in two distinct ways:
@@ -59,7 +61,6 @@ These are the six possible situations at the time of bullseye (buster + 1):
 * `middle`: both directory schemes are allowed, packages can be built anywhere
 * `hard`: both directory schemes are allowed, packages only built on "merged `/usr`" hosts
 * `all`: only "merged `/usr`" directory schemes are allowed, packages only built on "merged `/usr`" hosts
-* `full`: only "merged `/usr`" directory schemes are allowed, symlinks have been removed
 
 It can be summarized by the following table:
 
@@ -72,7 +73,6 @@ It can be summarized by the following table:
 |   middle |       yes       |        yes        |        yes       |       yes       |        yes        |          no         |           no         |
 |     hard |       yes       |        yes        |        yes       |        no       |        yes        |          no         |           no         |
 |      all |       no        |        yes        |        yes       |        no       |        yes        |         yes         |           no         |
-|     full |       no        |        yes        |         no       |        no       |        yes        |         yes         |          yes         |
 ```
 
 ## Immediate actions