Setting the root password with virt-customize and virt-builder doesn't seem to work with libguestfs-1.27.50. Tested against a virt-builder fedora-20 image. It worked last week, so I downgraded arbitrarily to libguestfs-1.27.36, tried setting a password, and it worked. yum updated to latest, tried setting a password, and it failed, and the old password didn't work either.
Created attachment 940938 [details] Output from: sudo virt-customize -v -x --password root:password:1234AA -a fedora-20.img
Something to do with now using Augeas to edit the /etc/shadow file?
(In reply to Richard W.M. Jones from comment #2) > Something to do with now using Augeas to edit the /etc/shadow file? Indeed, the way Augeas writes the new file loses the SELinux context. Luckly we have the API for copying attributes. Patches posted: https://www.redhat.com/archives/libguestfs/2014-September/msg00281.html https://www.redhat.com/archives/libguestfs/2014-September/msg00282.html
Fixed with https://github.com/libguestfs/libguestfs/commit/5f9437ca4bb842b1e8ae91ffbf3c73820780c5a6 https://github.com/libguestfs/libguestfs/commit/35daabed8f6da1b6039c4fd32848dcff6347e0dd which are in libguestfs >= 1.27.56.