ref-manual/variables.rst: Add incompatibility warning for SERIAL_CONSOLES_CHECK

See [YOCTO #13921]

Add details to the SERIAL_CONSOLES_CHECK entry to clarify that it
doesn't work with read-only rootfs.

(From yocto-docs rev: cefd66301a40f9048499879674e467543f704c44)

Signed-off-by: Trevor Gamblin <trevor.gamblin@windriver.com>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Reviewed-by: Quentin Schulz <foss@0leil.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index 64521b89bb..3297a69edf 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -6694,7 +6694,11 @@ system and gives an overview of their function and contents.
          SERIAL_CONSOLES_CHECK = "slcp_line0:ttyS0"
 
       This variable is currently only supported with SysVinit (i.e. not
-      with systemd).
+      with systemd). Note that :term:`SERIAL_CONSOLES_CHECK` also requires
+      ``/etc/inittab`` to be writable when used with SysVinit. This makes it
+      incompatible with customizations such as the following::
+
+         EXTRA_IMAGE_FEATURES += "read-only-rootfs"
 
    :term:`SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS`
       A list of recipe dependencies that should not be used to determine