Disk structure error reported in Onyx but not fixable via the Disk Utility in Recovery Mode On Yosemite 10.10 Onyx returns the following error:


  Error: -69845: File system verify or repair failed Underlying error:
  8: POSIX reports: Exec format error
  The disk needs to be repaired.


I tried repairing the disk in recovery mode but the disk utility returns a message that everything is fine, however, the after running Onyx the second time the error persists.

On a related matter, the option to repair permissions is not available in the Disk Utility.
Disk Utility will not fix every conceivable disk corruption issue. For that you need third-party apps. I use Diskwarrior and have also had success with Drive Genius.

However there is one way to do this without buying a disk repair utility. Back up your hard drive, partition/reformat it, reinstall the OS and restore your backup. Yeah it's more complicated and a bit of a PITA but will save you money.