Re: [Libguestfs] [libguestfs PATCH] guestfs.pod: document encrypted RBD disk limitation

Under "REMOTE STORAGE", the "NETWORK BLOCK DEVICE" section already documents some limitations. Turns out we need to describe a quirky exception for accessing encrypted RBD disks, too. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2033247 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; --- lib/guestfs.pod | 33 ++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/lib/guestfs.pod b/lib/guestfs.pod index b04c28d62750..1ad44e7c2878 100644 --- a/lib/guestfs.pod +++ b/lib/guestfs.pod @@ -679,6 +679,39 @@ servers. The server string is documented in L</guestfs_add_drive_opts>. The C<username> and C<secret> parameters are also optional, and if not given, then no authentication will be used. +An encrypted RBD disk -- I<directly> opening which would require the +C<username> and C<secret> parameters -- cannot be accessed if the +following conditions all hold: + +=over 4 + +=item * + +the L<backend|/BACKEND> is libvirt, + +=item * + +the image specified by the C<filename> parameter is different from the +encrypted RBD disk, + +=item * + +the image specified by the C<filename> parameter has L<qcow2 +format|/COMMON VIRTUAL DISK IMAGE FORMATS>, + +=item * + +the encrypted RBD disk is specified as a backing file at some level in +the qcow2 backing chain. + +=back + +This limitation is due to libvirt's (justified) separate handling of +disks vs. secrets. When the RBD username and secret are provided inside +a qcow2 backing file specification, libvirt does not construct an +ephemeral secret object from those, for Ceph authentication. Refer to +L<https://bugzilla.redhat.com/2033247>. + =head3 FTP, HTTP AND TFTP