I recently upgraded to Yosemite, enabled FileVault and foolishly enabled TRIM (had no idea it wasn't supported).
Upon restart, my machine gets the grey screen with the crossed-out circle of death.
After figuring out what happened, I then attempted to restore from a Time Machine backup (10.9). The backup failed almost immediately, but did manage to erase the HD (or at least the partition is gone).
Now I'm completely stuck. Disk Utility can see this drive, but cannot erase or re-partition it. The drive isn't mounted so I cannot access it with Terminal (at least with my level of knowledge). cd /Volumes/mydrive doesn't work – no such directory.
I have re-installed Yosemite on my second hard drive and booted from there. I tried Disk Utility again and I still have no options available to erase or partition my original disk, although it is there.
Can anyone help me get my original disk back into functioning form? If I can just get the disk erased and partitioned, I can load my Time Machine backup and be off to the races. Thanks!
Best Answer
A clean install is not necessary, you simply need to reconfigure your NVRAM (nvram boot-args=kext-dev-mode=1) to disable the kext signing requirement for OS X. (After which, you can remove your TRIM enabler and reverse this change or leave it until the next time your NVRAM is changed/resets)
A very clear explanation of OS X 10.10 Yosemite's new policy with Kernel Extension (kext) signing now being required from the creator of Trim Enabler, as well as simple steps to recover the grey boot screen after TRIM/Yosemite mishaps:
https://cindori.org/trim-enabler-and-yosemite/