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Re: User-installable Debian packages?

On Sat, 22 Jul 2017 at 12:28:04 +0200, Steffen Möller wrote:
> And quite some packages in our
> distribution do not really need to be installed as root if they were
> installed where the user has write permissions. There would hence be
> little overhead over what we have now. Should we not somehow find ways
> to tag any such location-agnostic packages and prepare dpkg for
> installing e.g. in $HOME/.debian when it is executed as non-root?

Rather than inventing a new wheel and having another Debian-specific
thing that can only be used on Debian (and not even on derivatives
without it being a "Frankendebian" system), might it be better to use
Debian's source, binaries or a mixture of the two as input to creating
something cross-distribution like Flatpak, AppImage or Snap? I would
personally recommend Flatpak.

A Flatpak runtime (the library/platform layer shared by multiple Flatpak
apps) is basically just a copy of /usr after applying the /usr merge (as
in usrmerge or debootstrap --merged-usr). The reference runtimes
produced by Flatpak upstream consist of a Yocto base system with
flatpak-builder build scripts (flatpak-builder is a bit like Flatpak's
equivalent of debhelper) layering useful libraries above it; but there
is nothing to stop a distribution from building their own runtimes from
dpkg or RPM packages without using flatpak-builder, and I believe Fedora
and Endless are already doing this. Debian could too.

A Flatpak app (the user-facing part) is basically the app and any bundled
libraries that are needed in addition to what's in the runtime, all
built with --prefix=/app. Again, the apps produced by upstreams like
GNOME and KDE are typically built from source with flatpak-builder,
but that is not required. I believe Fedora are already building their
leaf packages into Flatpak apps using their normal RPM spec files (which
are mostly position-independent), by overriding the prefix used for their
standard macros to /app.  Relocatable packages like the ones you describe
are trivial to convert into a Flatpak app (just move the files around,
like I did for rxvt in http://smcv.pseudorandom.co.uk/2016/xdg-app/ -
xdg-app is the old name for Flatpak). Non-relocatable packages (those
that hard-code paths) need rebuilding from source, but I have some ideas
about using dh-exec to parameterize the packaging (a bit like the way it
works in RPM spec files, but simpler) so that can be done automatically.

If this interests you, there are two talks at Debconf that you could
attend or stream, both on Monday: one by Cosimo Cecchi of Endless,
covering both OSTree and Flatpak, and one by me, focusing on Flatpak.
I'm hoping to have a proof-of-concept Debian runtime and a couple of
apps that use it (probably games) ready by the time I give my talk.