The current index at 'http://libguestfs.org/download/builder/index.asc' contains duplicate entries for 'fedora-21' corresponding to the x86_64 and aarch64 architectures. Talking with @rwmjones on IRC it was found that the current index works with virt-builder v1.28 but fails for me with v1.24.5 which is the version currently available on Ubuntu 14.04 LTS. I've been told that the necessary support was added in v1.26.
This happens because I added the fedora-21 aarch64 image.
Assigning to Pino.
I have added a patch to the libguestfs stable-1.24 branch which
Currently Ubuntu 14.04 is using an old version of libguestfs, and
not even the latest version of libguestfs along the 1.24 stable
branch. I highly recommend that Ubuntu updates to 1.24.9, which
includes this fix and a number of security fixes too. It should
be completely safe to update to 1.24.9 since the stable branch
only takes simple bug and security fixes.
However if that is not possible for some reason then taking just
the above patch will fix the current bug.
*** Bug 1276721 has been marked as a duplicate of this bug. ***
This is long fixed, see comment 2.
*** Bug 1284274 has been marked as a duplicate of this bug. ***
*** Bug 1323919 has been marked as a duplicate of this bug. ***