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
The current code checks if /boot/uEnv.txt is a symlink to
decice if sysroot requires u-boot support. Why this is bad:
There are 2 ways to provide a custom env to u-boot from user space:
1) A compiled binary that is sourced from u-boot.
2) A text file (usually /uEnv.txt) that is imported into env from u-boot.
The current OSTree u-boot integration code was designed with the 1st
case in mind.
Many bootscripts provided by an embedded device vendors expect
to find uEnv.txt in the top level directory, it is often hardcoded
when building u-boot and is difficult to change later on. Or in other
cases it is stored in read-only memory so changing it would require
re-flushing boot loader with a new env. So the issue here is that
OSTree's and vendor uEnv.txt want to exist and the same path and OSTree
would throw away any changes added to /uEnv.txt by user on the next
upgrade/deploy.
This patch "hides" away the OSTree's env file loader/uEnv.txt from users
who are used to edditing uEnv.txt at the top level directory. Now to add
OSTree support on such boards you can simply add a custom logic in uEnv.txt
that loads ostree env from /loader/uEnv.txt
This change is backward compatible with the previous ostree releases and
solves the issue described in:
https://bugzilla.gnome.org/show_bug.cgi?id=755787
Gatis Paeglis