Disk not mounting after enabling TRIM I enabled the TRIM for my SSD on my MacbookPro using Chameleon SSD, and now the Mac doesn't boot any longer. I have tried to follow guides to reverse the TRIM but none of them actually work because my disk appears to be not mounted and does not appear in /Volumes/

When I open the Disk utility, the disk is greyed. If I try to mount it, I get an error : Try repairing the disk. And of course, when I run a repair, it fails too. 

Sadly I have no recent backup (of course, would be too easy).

How can I mount this volume and reverse the TRIM enable?
Don't panic! I hope you haven't done irreparable damage with the disk utilities and partitioning, which has nothing to do with the problem. The fix is actually very simple.

The grey screen is caused by the non-signed kernel driver for the SSD. Mac OS X won't allow it to load by default, thus you can't access the boot disk.

This can happen if you don't turn off the kernel signing check, or if it gets turned on, which it often does during a system update.

If you are using Trim Enabler, this article describes how to recover. A similar procedure should work for anything that turned on trim. 

I'm using a Crucial SSD too, with trim enabled. I forgot to turn Trim off before a system update, and had to recover using the instructions on the linked page (successfully).

Basically it overrides the kernel signing check once again, so you can boot your Mac like before.

https://www.cindori.org/trim-enabler-and-yosemite/

Once I was back in, I used the trimforce command to prevent the problem in the future ;-) Trimforce is new in Yosemite, I believe.