The previously downloaded combined updaters for 10.6.8 and 10.11.4 will run on their respective partitions, even with modified system folders (fonts). I restored original fonts to my 10.10.5 partition and still the updater would not run. I downloaded a fresh combo updater to my MacBook and it, too, refused to run saying again, "This volume does not meet the requirements for this update."
I ran into a similar problem with one of the Yosemite betas. It turned out if the drive was partitioned, Yosemite would only install and work correctly on the
first partition.
[quoite=freelance]I decided to bite the bullet and run the original Yosemite 10.10.0 system installer. But, the installer would not be verified, saying it was possibly corrupted and go to the App Store and download a new copy. I went to previous my purchases on the App Store. Every OS back to Lion was listed for download, but not Yosemite.[/quote]
AFIK any Mac that will run Yosemite will also run El Capitan, so it makes economic sense for Apple to move users to El Capitan.
