[bug#41189] [PATCH 0/3] Add Fakechroot engine for 'guix pack -RR'

["Ludovic Courtès" <ludo@gnu.org>]

Hello Guix!

‘guix pack -RR’ is wonderful, as we know ;-), because it produces
binaries that work everywhere.

However, the overhead of PRoot is sometimes inappropriate, in
particular for those who want to run packed software on
high-performance computers, the very kind of machine that lacks
Guix and unprivileged user namespaces.

This patch series adds an optional “execution engine” to wrappers
that uses ld.so and fakechroot LD_PRELOAD trickery.  Since it’s
just LD_PRELOAD, there’s very little overhead, unlike PRoot.
On the flip side, it doesn’t work as well as PRoot, because it’s
“just” LD_PRELOAD.

For example, some of the ‘open’ calls made in libc are not
intercepted; on such call is in ‘__gconv_load_cache’, which makes
it fail, and in turn makes Guile fail to start in its first
‘scm_to_locale_string’ call.  Things that work well include Bash
and Python 3.  Let me know how well it works for your favorite
application!

The execution engine can now be chosen at run time by setting the
‘GUIX_EXECUTION_ENGINE’.

For the record, tools like udocker support a similar range of
execution engines: <https://github.com/indigo-dc/udocker/>.

Feedback welcome!

Thanks,
Ludo’.

Ludovic Courtès (3):
  pack: Wrapper honors 'GUIX_EXECUTION_ENGINE' environment variable.
  gnu: Add fakechroot.
  pack: Add relocation via ld.so and fakechroot.

 doc/guix.texi                             |  43 +++-
 gnu/packages/aux-files/run-in-namespace.c | 250 ++++++++++++++++++++--
 gnu/packages/linux.scm                    |  30 +++
 guix/scripts/pack.scm                     |  65 +++++-
 tests/guix-pack-relocatable.sh            |  23 ++
 5 files changed, 376 insertions(+), 35 deletions(-)

-- 
2.26.2