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-rw-r--r--docs/system/deprecated.rst12
-rw-r--r--docs/tools/qemu-img.rst4
2 files changed, 16 insertions, 0 deletions
diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index c014e049c3..c1f019b9d2 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -427,6 +427,18 @@ kernel in 2018, and has also been dropped from glibc.
Related binaries
----------------
+qemu-img amend to adjust backing file (since 5.1)
+'''''''''''''''''''''''''''''''''''''''''''''''''
+
+The use of ``qemu-img amend`` to modify the name or format of a qcow2
+backing image is deprecated; this functionality was never fully
+documented or tested, and interferes with other amend operations that
+need access to the original backing image (such as deciding whether a
+v3 zero cluster may be left unallocated when converting to a v2
+image). Rather, any changes to the backing chain should be performed
+with ``qemu-img rebase -u`` either before or after the remaining
+changes being performed by amend, as appropriate.
+
Backwards compatibility
-----------------------
diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
index e33f5575e3..c35bd64822 100644
--- a/docs/tools/qemu-img.rst
+++ b/docs/tools/qemu-img.rst
@@ -258,6 +258,10 @@ Command description:
Amends the image format specific *OPTIONS* for the image file
*FILENAME*. Not all file formats support this operation.
+ The set of options that can be amended are dependent on the image
+ format, but note that amending the backing chain relationship should
+ instead be performed with ``qemu-img rebase``.
+
--force allows some unsafe operations. Currently for -f luks, it allows to
erase the last encryption key, and to overwrite an active encryption key.