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(a)redhat.com&gt; --- 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

Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- docs/news.xml | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/docs/news.xml b/docs/news.xml index f69c9c4780..0b67c4dcc2 100644 --- a/docs/news.xml +++ b/docs/news.xml @@ -113,8 +113,31 @@ exposes the same capability to libvirt users. </description> </change> + <change> + <summary> + qemu: Storage configuration improvements + </summary> + <description> + Libvirt now accepts <code>&lt;backingStore type='volume'&gt;</code> + and allows to specify the offset and size of the image format + container inside of the storage source via the <code>&lt;slices&gt;</code> + subelement. + </description> + </change> </section> <section title="Improvements"> + <change> + <summary> + qemu: Image format probing is allowed in certain cases + </summary> + <description> + To resolve regressions when users didn't specify the backing image + format in the overlay libvirt now probes the format in certain + secure scenarios which fixes few common existing cases. Additionally + the knowledge base was extended to provide more information how + to rectify the problem. + </description> + </change> </section> <section title="Bug fixes"> </section> -- 2.24.1