Why not to use libexecdir?
Because this directory does not exist on some distros or paths
between distros varies. There are several reasons why a well
known path is prefered, for example when generating a kernel
command line:
init=${ostree}/usr/lib/ostree-boot/ostree-prepare-root
In addition this saves us some typing in a console when wanting
to access the "ostree" cmd line.
Closes: #449
Approved by: cgwalters
ostree-grub-generator can be used to customize
the generated grub.cfg file. Compile time
decision ostree-grub-generator vs grub2-mkconfig
can be overwritten with the OSTREE_GRUB2_EXEC
envvar - useful for auto tests and OS installers.
Why this alternative approach:
1) The current approach is less flexible than using a
custom 'ostree-grub-generator' script. Each system can
adjust this script for its needs, instead of using the
hardcoded values from ostree-bootloader-grub2.c.
2) Too much overhead on embedded to generate grub.cfg
via /etc/grub.d/ configuration files. It is still
possible to do so, even with this patch applied.
No need to install grub2 package on a target device.
3) The grub2-mkconfig code path has other issues:
https://bugzilla.gnome.org/show_bug.cgi?id=761180
Task: https://bugzilla.gnome.org/show_bug.cgi?id=762220Closes: #228
Approved by: cgwalters
In this approach, we drop a /etc/grub.d/15_ostree file which is a
hybrid of shell/C that picks up bits from the GRUB2 library (e.g. the
block device script generation), and then calls into libostree's
GRUB2 code which knows about the BLS entries.
This is admittedly ugly. There exists another approach for GRUB2 to
learn the BLS specification. However, the spec has a few issues:
https://www.redhat.com/archives/anaconda-devel-list/2014-July/msg00002.html
This approach also gives a bit more control to the admin via the
naming of the 15_ostree symlink; they can easily disable it:
Or reorder the ostree entries ahead of 10_linux:
Also, this approach doesn't require patches for grub2, which is an
issue with the pressure to backport (rpm-)OSTree to EL7.
tmpfiles.d configurations generally require write access to some places
that are read-only until ostree-remount runs.
Make sure ostree-remount has run first.
Thanks to Cosimo Cecchi for finding and diagnosing this problem.
https://bugzilla.gnome.org/show_bug.cgi?id=724183
Simon McVittie
Colin Walters
Gatis Paeglis
Gatis Paeglis
Giuseppe Scrivano
Daniel Drake
Daniel Narvaez