Bug#1064459: base-files: install aliasing symlinks for merged-/usr DEP17

[Helmut Grohne]

Package: base-files
Version: 13
Tags: patch moreinfo
X-Debbugs-Cc: jul...@debian.org

Do not upload this patch to unstable yet!

Hi,

We are about to finalize the /usr-merge transition by moving all files
to their physical location. In the process, we want to move the actual
aliasing symbolic links from debootstrap/usrmerge into an actual
data.tar. The ideal package for this seems to be base-files. I've
prepared a patch for doing this.

I'll explain some of the choices made in the patch now as they may be
non-obvious.
* We're installing the aliasing symlinks as relative links despite
lintian complaining about this. The links that usrmerge and
debootstrap install are also relative and relative links make working
with chroots more convenient.
* base-files will "Provides: usr-is-merged". Future installations will
contain neither usrmerge nor a physical usr-is-merged package.
* base-files will install multilib directories when the dynamic loader
needs them. For instance on amd64, the dynamic loader path is
/lib64/ld-linux-x86-64.so.2. Therefore base-files:amd64 will include
/lib64. All other multilib directories will not be installed to
data.tar.
* For all non-essential multilib directoires, base-files declares a
trigger interest in the physical location and adds/removes the
aliasing symlink as-needed. This way, we do not have all of
lib32, lib64, libo32 and libx32 on every Debian installation.
* The patch proposed to glibc relies on these triggers to create these
multilib links for their multilib packages. If we change this aspect,
we must also change the glibc patch #1061248.
* base-files.preinst will now validate the aliasing symlinks as
usr-is-merged did. In a bootstrap setting, base-files is unpacked
before base-files.preinst and in an upgrade scenario we should be
merged already.

This patch needs to be uploaded concurrently with bash, dash, glibc and
util-linux failing to do so will break bootstrapping tools. I intend to
NMU this patch at an appropriate and coordinated time. I'm happy to
receive feedback on it already.

This mail is interesting to Julian, because he'll do the same changes to
Ubuntu just earlier than Debian. We're in the glad position that Ubuntu
will test this for us.

Helmut

[Santiago Vila]

Hi.

Please respect any already existing coding style that
you can notice in other parts of base-files.

Some examples:

Indent in shell script using 2 spaces.
Quotes around "triggered" and similar places.

(Also, I wonder if it would be possible to create debian/triggers
using some sort of dh-exec-like template instead of having
extra variables and a for loop in debian/rules).

While we are at it: Is there an estimated date when you will want
to upload this?

Thanks.