Ok. So I was looking into this more, suspecting that uec-publish-tarball was in fact, buggy.
However, it looks like the bug is in Eucalyptus is buggy in its use of images that are registered without a ramdisk.
If you register image A with a ramdisk, and then register image B without a ramdisk, and start instance B, then it will be booted with the ramdisk registered with image A.
Ok. So I was looking into this more, suspecting that uec-publish-tarball was in fact, buggy.
However, it looks like the bug is in Eucalyptus is buggy in its use of images that are registered without a ramdisk.
If you register image A with a ramdisk, and then register image B without a ramdisk, and start instance B, then it will be booted with the ramdisk registered with image A.