We document steps how to fix images if they are rejected for missing the 'backing file format' field. Document also how to securely probe the image format if its unknown. Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx> --- docs/kbase/backing_chains.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/docs/kbase/backing_chains.rst b/docs/kbase/backing_chains.rst index 12ed6253ac..af848ccb14 100644 --- a/docs/kbase/backing_chains.rst +++ b/docs/kbase/backing_chains.rst @@ -176,6 +176,21 @@ properly. ``$BACKING_IMAGE_PATH`` should be specified as a full absolute path. If relative referencing of the backing image is desired, the path must be relative to the location of image described by ``$IMAGE_PATH``. +**Important:** If the ``$BACKING_IMAGE_FORMAT`` is not known it can be queried +using ``qemu-img info $BACKING_IMAGE_PATH`` and looking for the ``file format:`` +field, but for security reasons should be used *only* if at least one of the +following criteria is met: + +- ``file format`` is ``raw`` +- ``backing file`` is NOT present +- ``backing file`` is present AND is correct/trusted + +Note that the last criteria may require manual inspection and thus should not +be scripted unless the trust for the image can be expressed programatically. + +Also note that the above steps may need to be repeated recursively for any +subsequent backing images. + Missing images reported after after moving disk images into a different path ---------------------------------------------------------------------------- -- 2.24.1
