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

On Wed, May 18, 2022 at 10:30:14AM +0200, Laszlo Ersek wrote: > 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 Seems fine. I had to look at perlpod(1) to check that the piped L<> references were correct, but they seem to be! Acked-by: Richard W.M. Jones <rjones(a)redhat.com&gt; Rich.