[OS-BUILD PATCH] redhat/docs: Add FAQ entry for booting between Fedora & ELN/RHEL kernels

[Prarit Bhargava (via Email Bridge)]

From: Prarit Bhargava <prarit(a)redhat.com&gt;

redhat/docs: Add FAQ entry for booting between Fedora & ELN/RHEL kernels

Add an FAQ entry that provides some simple debugging suggestions for
booting between Fedora and ELN/RHEL kernels.

Signed-off-by: Prarit Bhargava <prarit(a)redhat.com&gt;

diff --git a/redhat/docs/faq.rst b/redhat/docs/faq.rst
index blahblah..blahblah 100644
--- a/redhat/docs/faq.rst
+++ b/redhat/docs/faq.rst
@@ -35,8 +35,18 @@ resolve this properly.
 Please notify us on kernel(a)lists.fedoraproject.org or file an issue at
 https://gitlab.com/cki-project/kernel-ark/-/issues.
 
+3.  I am booting an ELN/RHEL kernel on Fedora (or vice versa) and the kernel won't
boot.  What do I do now?
 
-3. How does an MR get reviewed?
+This is not uncommon and may be due to a config difference between RHEL and Fedora.  One
key difference between the two kernels is that Fedora has enabled CONFIG_BTRFS where
ELN/RHEL has not, and as a result ELN/RHEL kernels will not mount Fedora BTRFS
filesystems.  If you are booting the ELN/RHEL kernel config on Fedora you must change
these configuration values in the .config:
+
+.. code-block:: sh
+
+   CONFIG_BTRFS=y
+   CONFIG_BTRFS_FS_POSIX_ACL=y
+
+If that change doesn't resolve the boot failure, users should attempt to
"flip" configs to determine the difference between the two flavors before
reporting bugs.  The maintainers acknowledge that this can be a time consuming process but
it is left to the user to resolve config differences when cross booting between flavors.
+
+4. How does an MR get reviewed?
 -------------------------------
 
 Anything Fedora specific (configs, custom patches, scripts) will be decided

--
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/2239