How did yoy use OnyX to clear/delete/whatever because I couldn't figure it out..
So, I set Yosemite as my Startup Disk from within Mavericks, and rebooted with the Shift key depressed into Yosemite Safe Boot.
Loaded OnyX in an Admin account while in Safe Boot, let it check SMART status and Verify, then--frankly--I stared at the bar with the icons for a few seconds, wondering what to do . . . Jay-bug said "rebuild", so I poked around, and found the Maintenance -> Rebuilding tab, but nothing that said 'boot', so I poked around further.
Selecting "Cleaning", I found "Delete the cache:" with 'Boot, Kernel, etc., &c.". Pondered that for a few . . . 'delete'? I just want to rebuild . . . .
I have copies of copies of different OSX backups at multiple stages, so I thought I might as well give it a try . . . I could always go back to a bootable installation (three active on local fixed disks), re-image the basic Yose backup if I did something wrong, and do it again.
One thing I did do before 'Execute' was to uncheck everything but "Boot" and "Other system components".
After a "Restart" back into Yosemite, I was greeted with the ever-persistent LS popups with a fresh install with lots of questions....
I was--of course--more concerned about my question ("Will this work?", the inherent irony being that the expected answer was in the form of more questions <s>
hth