Setting Trim _AFTER_ a New Install

Warren Block wblock at
Thu Apr 9 21:27:35 UTC 2015

On Thu, 9 Apr 2015, mfv wrote:

> Hello,
> I've recently installed FreeBSD r10.1 using bsdinstall and then loaded
> a large number of programs and data.  After spending considerable time
> on the installation I discovered that my SSD has TRIM which appears
> to be quite useful. After some investigation I understand that it is a
> simple flag that can be set after booting into single user mode.
> I hope my questions are  simple:
> If TRIM is enabled will it mess up the disk so that everything has to be
> reinstalled?

No, it will not harm the data.  That said, before running tunefs to 
enable it, make a backup.  Always make a backup.

> If not, is there anything else I should be aware of?

If you used ZFS-on-root, tunefs(8) and TRIM do not apply.  ZFS uses TRIM 
natively now, but I'm not sure if that was in 10.1 or only now in 

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