Update on Trim in Yosemite

Update on Trim in Yosemite
July 30, 2014 Oskar

This is an old post. Please see the latest post on Trim in Yosemite:





The state of Trim in Yosemite

As some users may have noticed, if you try to enable Trim on OS X Yosemite, you can get stuck with a grey screen with a stop sign during boot. And as detailed in these two posts., this issue was due to a new feature in OS X Yosemite.

In OS X 10.10 (Yosemite), Apple has introduced a new security requirement called kext signing. (A kext is a kernel extension, or a driver, in Mac OS X)

Kext signing basically works by checking if all the drivers in the system are unaltered by a third party, or approved by Apple. If they have been modified, Yosemite will no longer load the driver. This is a step by Apple to lock out anyone from making software that interacts with the system, to make the Mac experience more and more similar to iOS.

Since Trim Enabler works by unlocking the Trim driver for 3rd party SSD’s, kext signing prevents Trim Enabler to enable Trim on Yosemite, at least out of the box.

Currently, there is only one way to continue to use Trim Enabler and continue to get Trim for your third party SSD, and that is to disable the kext signing requirement.

While it is unfortunate to have to disable kext signing, it still leaves you with the same amount of security as in OS X Mavericks, where the kext signing requirement didn’t exist.

Trim Enabler 3.2.5 Update

I have released a Trim Enabler 3.2.5 update, which is adapted for Yosemite:

  • Trim Enabler can now disable kext signing in order to enable Trim on Yosemite
  • Fixed an issue with Trim Enabler not launching on Yosemite DP4 / Beta

Apple is locking down the Mac

It’s becoming clear that Apple wants to block applications from altering the OS X experience. While disabling kext-signing still allows Trim Enabler to work, I wish the process of enabling Trim would be smoother. The first thing that comes to mind is to create a kernel extension that somehow achieves this purpose. But as detailed here:

Kext signing means that a valid, signed kernel extension can only be created with a certificate provided by Apple as part of their $99/yr Developer program, and additionally that interested parties must fill out a special form explaining why they require the certificate; kext certificates are only provided upon request and approval.

Apple now effectively controls which kexts are allowed on OS X, and thus, what features that developers like me can release for OS X. And since Apple has made such an effort to block third party SSD’s from getting Trim support in OS X, my guess is that if someone were to make such a kext, Apple would deny a certificate, making it impossible to distribute. So for now, using Trim Enabler 3.2.5 and later is the best way to enable Trim on OS X.

I believe that Apple’s new direction for OS X is unfortunate and ultimately will end up greatly limiting Pro users in favor of usability for casual users. I don’t think it’s long before we will have to start “jailbreaking” our Macs as well.

Recovering from stop sign on boot screen

For those who are stuck on the grey boot screen, here’s how you get back into OS X:



If you want to discuss Trim Enabler and Yosemite, use the sticky topic on the forum: Trim Enabler in Yosemite

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