[Reproducible-builds] Bug#769844: linux: please make linux build reproducibly

[Jérémy Bobbio]

Control: unblock -1 by 759886

Jérémy Bobbio:
> Bastian Blank:
> > On Mon, Nov 17, 2014 at 12:46:45AM +0100, Jérémy Bobbio wrote:
> > > The first patch adds call to `dh_strip_nondeterminism` and
> > > `dh_fixmtimes`, both being part of the custom toolchain currently used
> > > for reproducible builds. Hence not tagging the bug with “patch” until
> > > they are integrated in debhelper.
> > 
> > Why does this need new tool instead of being integrated into the
> > existing ones?
> 
> I am not sure which ones you specifically have in mind, but the whole
> project is still at the experimental stage. We try to work in
> unintrusive ways.

We are currently experimenting with fixing mtimes in `dh_builddeb`
instead of requiring a new helper. I have also done my latest
experiments without `dh_strip_nondeterminism`. The attached patch adds
the `-n` flag to gzip to compensate.

> > > The second patch changes the value of KBUILD_BUILD_TIMESTAMP to a
> > > timestamp parseable by `date`.
> > 
> > Well, no.  The string is this way for a reason.
> 
> Would a patch against `scripts/gen_initramfs_list.sh` to make it parse
> Debian's KBUILD_BUILD_TIMESTAMP be acceptable then? Any other
> suggestions?

Implemented in the attached patch.

> > > An unclear aspect is where to add a call to `dh_genbuildinfo` which
> > > generates the .buildinfo [2]. It should be called after all binary
> > > packages have been created.
> > 
> > Not possible, dh_* acts on single binary packages.
> 
> Mh… I'm not sure we had realized that. It makes a case to move the
> generation of the .buildinfo closer to dpkg-genchanges.

That's how the experimental toolchain now works: the .buildinfo is
generated by dpkg-genbuildinfo, called by dpkg-buildpackage.

> > >  * linux-source: mtimes of many files differ. Would it be ok to just
> > >    create the tarball with a single timestamp (`tar --mtime=`)?
> >
> > Looks like a way.
> 
> Good. :) I will experiment with this approach and probably add another
> patch to this bug report.

I've used find+touch instead. See attached patch.


With the attached patch, my latest build+rebuild showed similar
differences in linux-doc and linux-manual. It is probably related to the
way API documentation is currently extracted from the source code.

I also stumbled on a variation of the Installed-Size field in one of the
.deb. But this is a different topic.

-- 
Lunar                                .''`. 
lunar at debian.org                    : :Ⓐ  :  # apt-get install anarchism
                                    `. `'` 
                                      `-   
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