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I am using 2009 macbook pro and I wanted to upgrade the default hdd to a Samsung Evo 850. I have succeeded to transfer everything from a Time Machine backup, but when I wanted to enable the trim by sudo trimforce enable, then after a restart computer just shows the "crossed out circle". I am running OSX 10.11.6, and AFAIK it should just work. Am i missing something there?

What I did exactly is:

  • put a clean ssd into the computer
  • booted from USB install disk for El Capitan
  • restored the backup from the time machine
  • logged in successfullty to a newly setup osx as a user with admin rights,
  • saw in system information SATA suport "Trim support: no"
  • in Terminal typed sudo trimforce enable, after a minute computer reboot
  • crossed out circle shows (every 10 seconds it changes for approx 0.3 seconds for apple logo, but the computer does not boot)

am I missing something?

Edit. On page Crindori Disk sensei I found:

This is the easiest and safest way to enable Trim on OS X.
It is even better than using the new built in trimforce command,
since that requires 10.10.4 and may require disabling system security on El Cap.

Are they up to something with "disabling system security on El Cap". Should I still have done the kext-dev-mode=1 thing?

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  • Have you tried the usual: NVRAM and SMC reset, boot into repair mode and run disk utility?
    – n1000
    Feb 11, 2017 at 6:46
  • I could not get it to run in repair mode. When pressing cmd+R, the crossed out circle appears too (this time not immediately after boot sound but 10 minute later). I used repair mode from USB drive, ring first aid on SSD - it passed reported no error. I did reset NVRAM, did not try SMC.
    – user68358
    Feb 11, 2017 at 6:56
  • You could try alt+cmd+R for internet recovery: support.apple.com/en-us/HT201314
    – n1000
    Feb 11, 2017 at 7:04
  • Please avoid making your question a "moving target" by editing it. You can always ask a new question. Normally trimforce should work (without kext-dev-mode=1). There are many examples (including me) where it worked without problems.
    – n1000
    Feb 11, 2017 at 7:13
  • Ok, internet recovery also does not work - stop sign pops up. I can boot only from usb stick.
    – user68358
    Feb 11, 2017 at 7:15

2 Answers 2

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I'm using a Samsung 850 EVO in my MacBook Pro. If you prefer a method that uses the GUI, I recommend Trim Enabler (it's $9.99, works well, and supports the EVO 850):

You also asked why they mentioned that trimforce might not be safe. This article in their FAQ might answer your question: Why should I not use Terminal commands like trimforce?

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  • The second link is dead.
    – nalzok
    Apr 30 at 7:57
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I have read several forum posts reporting similar problems.

This article says that indeed El Capitan system security may be your problem and that you should use their software (Disk Sensei).

This article describes the procedure to get your system back. Some users also report they were able to make TRIM work with this procedure:

Follow these steps to disable kext-signing and rebuild your kext cache.

Step 1: Boot recovery mode by holding Cmd+R during boot

Step 2: Is your volume encrypted (FileVault)? If so, first open Disk Utility from the menu bar and unlock/mount your drive

Step 3: Open the Terminal from the menu bar

Step 4: Run this command: nvram boot-args

Does it say “kext-dev-mode=1”? if so, you can skip to Step 6. If it says “error getting variable”, continue with these steps:

Step 5: Run this command: nvram boot-args=kext-dev-mode=1

Step 6: Reboot back in to Recovery Mode again

Step 7: Run these commands, replacing Your Disk Name with the name of your Mac disk volume. If the volume name contains spaces, use quotes around it.

touch /Volumes/"Your Disk Name"/System/Library/Extensions

kextcache -u /Volumes/"Your Disk name"

Step 8: Wait until it finishes (can take as long as 5-10 minutes, don’t abort it) and reboot.

You should now be back in OS X with Trim enabled

There is also a second manual on how to reverse all TRIM changes:

Follow these steps to undo all changes made by Trim Enabler.

Step 1: Boot recovery mode by holding Cmd+R during boot Step 2: Is your volume encrypted (FileVault)? If so, first open Disk Utility from the menu bar and unlock/mount your drive

Step 3: Open the Terminal from the menu bar

Step 4: Run these commands, replacing Your Disk Name with the name of your Mac disk volume. If the volume name contains spaces, use quotes around it.

nvram -d boot-args

cp -rf /System/Library/Extensions/IOAHCIFamily.kext /Volumes/"Your Disk name"/System/Library/Extensions/IOAHCIFamily.kext

chown -R root:wheel /Volumes/"Your Disk name"/System/Library/Extensions

chmod -R 755 /Volumes/"Your Disk name"/System/Library/Extensions

touch /Volumes/"Your Disk name"/System/Library/Extensions

kextcache -u /Volumes/"Your Disk name"

Step 5: Wait until it finishes (can take as long as 5-10 minutes, don’t abort it) and reboot.

You should now be back in OS X with Trim disabled.

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