Bug#943434: Please add /etc/alternatives in the list of directories bind-mounted by bubblewrap

[Raphaël Halimi]

Package: libgnome-desktop-3-18
Version: 3.34.1-1
Severity: minor
Affects: ffmpegthumbnailer libblas3

(As advised in #902288, I'm reporting the bug against libgnome-desktop
instead of ffmpegthumbnailer or libblas, adding them as affected by the bug)

Hi,

I use ffmpegthumbnailer instead of totem-thumbnailer to generate
thumbnails in Nautilus. For maybe a week or so (but since I rarely
reboot my Sid machine or logout from this session, the upgrade which
triggered this bug may be older than that), I noticed that the
thumbnails were not generated anymore.

By manually running a command similar to the one used by nautilus to run
the thumbnailer in bubblewrap, I have this error message:

ffmpegthumbnailer: error while loading shared libraries: libblas.so.3:
cannot open shared object file: No such file or directory

It turns our that /usr/lib/x86_64-linux-gnu/libblas.so.3 is a symlink
pointing to /etc/alternatives/libblas.so.3-x86_64-linux-gnu, itself
pointing to /usr/lib/x86_64-linux-gnu/blas/libblas.so.3. So the library
is actually in the container, but the binary can't find it because of
the symlink in /etc/alternatives, which isn't bind-mounted.

By adding "--ro-bind /etc/alternatives /etc/alternatives" to the bwrap
command line, ffmpegthumbnailer didn't complain anymore and the
thumbnail was generated as expected.

I think it would be nice to patch the Debian package of libgnome-desktop
to also bind /etc/alternatives when running a command in bubblewrap, as
ffmpegthumbnailer may not be the only binary run by Nautilus through
bubblewrap that may need stuff in /etc/alternatives (now or in the future).

Since /etc/alternatives is Debian-specific, I think it shouldn't be
necessary to report this bug to upstream.

Regards,

-- 
Raphaël Halimi

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