Don't panic. If all goes well nothing will change from a nightly-build-user perspective. We are going to be moving to a more sane system for the generation of nightly .mar files and AUS2 snippets. Details below, but first, some background. Rob Helmer talked a lot about AUS and updates, mostly regarding releases. What he did not mention the silly path that our nightly updates take. All of our nightly updates currently take the following path:

1. Nightly build happens - this includes a complete MAR and complete AUS snippet
2. Cronjob on a specific build machine performs some magic and generates a partial MAR and partial AUS snippet

Once these changes land our 3.1 builds will take the following path:

1. Nightly build happens - this includes complete AND partial MAR, complete AND partial AUS snippet

(We could probably support Tinderbox driven builds (2.x, 3.x) pretty easily too, if someone wants to write the patch.) I think it's pretty obvious that this is a more sensible way to do things. As it stands now if we lose the VM that generates partials we lose all nightly updates. The hidden benefit here is that updates for releases and nightlies will have fewer differences between them. This means that problems with that system will be caught in the nightlies and *not* during a live release. (NB: We will still need to do snippets for older than n-1 builds, eg. 3.0->3.0.2 during the release process). I'm still doing testing of this but I hope to land these changes in mozilla-central/tools/update-packaging by the end of next week. Special note for build folks from SeaMonkey and Thunderbird: I will be replacing the CreateCompleteUpdateSnippet and snippet uploading ShellCommands with a couple Makefile targets - you may want to do the same.