Proposed as a F18 beta blocker due to violation of the following F18 beta release criterion [1] as building the upgrade initramfs is required for network upgrades:

For each one of the release-blocking package sets ('minimal', and the package sets for each one of the release-blocking desktops), it must be possible to successfully complete an upgrade from a fully updated installation of the previous stable Fedora release with that package set installed, using any officially recommended upgrade mechanisms. The upgraded system must meet all release criteria.

[1] http://fedoraproject.org/wiki/Fedora_18_Beta_Release_Criteria

Discussed at 2012-11-14 blocker bug meeting. Accepted as a blocker:  This prevents fedup from doing network upgrades and violates the following F18 beta release criterion: "... it must be possible to successfully complete an upgrade from a fully updated installation of the previous stable Fedora release with that package set installed, using any officially recommended upgrade mechanisms. The upgraded system must meet all release criteria."

https://admin.fedoraproject.org/updates/FEDORA-2012-18603/lorax-18.22-2.fc18 claims to fix this: -> MODIFIED

Just me doing my Bodhi impression, nothing to see here, continue about your business...

lorax-18.22-4.fc18 has been submitted as an update for Fedora 18.
https://admin.fedoraproject.org/updates/FEDORA-2012-18603/lorax-18.22-4.fc18

Confirming that there are upgrade.img initramfs files built with F18 beta RC1.

I did a test upgrade with fedup on a F17 x86_64 Gnome desktop install, pointing --instrepo at the RC1 os/ directory (where the .treeinfo is).

The upgrade succeeded, this appears to have been fixed.

lorax-18.22-4.fc18 has been pushed to the Fedora 18 stable repository.  If problems still persist, please make note of it in this bug report.

*** Bug 869064 has been marked as a duplicate of this bug. ***