Repurposing a personal mac

Hello Mac-forums:

I am repurposing my trusty 2014 macbook retina. It has been my personal computer for a while, but I just started a company, and so it is getting donated. However, before I lend this thing over night to inquisitive students or employees, I need to be as sure as possible that all of my personal data is gone. Wouldn't want pics or vids of the Director and his wife getting into the wrong hands, if you catch my meaning. TRIM is enabled (and has been for a long time) and the SSD is small, so even if it's not likely, that kind of data recovery is just not something I want to worry about.

However, replacing things is expensive, and I also really don't feel like justifying to various people why I spent 500 dollars to replace a perfectly functional Mac SSD. The best compromise is to as thoroughly as possible sanitize the drive and then reinstall OS X. I've heard that an ATA secure erase could do a very thorough job of getting rid of all the data on the drive. How would I implement this on my Mac Retina?

Thanks in advance for your help!
Justin

As far as secure erasing goes you need go no further than the native Disk Utility.
Your first step would be to download the El Capitan Installer from the App Store. If you already have El Capitan installed you will find the installer in your Purchases section of the App Store. it will say you already have it but say yes to download again.
Download a copy of Diskmaker X (for El Capitan) you will need to Google this but it's free.
Follow the instructions in Diskmaker X to create a bootable installer. You will need an external drive (thumb drive) of 8Gb plus to put it on.
Next boot up your MacBook holding the Option key, you should see the El Capitan Installer as a boot option, boot from that. Do not install the OS at this point, quit the installer.
Choose Disk Utility from the Menu bar.
Select your Macintosh HD and click erase. In erase Options you will be presented with levels of secure erase. If you choose the maximum level it will take a very long time and is unnecessary but this is up to you, I usually choose the second level option which is more than adequate.
After the disk is erased you can perform a clean instal of the operating system.
Quit and shut down at the beginning of the setup script and the person who you give it to will be able to setup like a new laptop.
BEFORE DOING THE ABOVE
Check the items below:
What to do before selling or giving away your Mac

When you get ready to sell or give away your Mac, there are some steps you should take. You'll want to back up your computer, disable some features and services, and erase the hard drive. This article shows you the steps you should follow.
Moving to a new Mac?
Learn how to move your files to your new Mac. Do this before you erase the hard drive or follow any other steps.
Create a backup
Be sure you have an up-to-date backup of your important files and data. Learn how to back up your data in OS X.
Sign out of iTunes
Open iTunes. From the menu bar at the top of your computer screen, choose Store > Deauthorize This Computer.
When prompted, enter your Apple ID and password. Then click Deauthorize.
Learn more about deauthorizing your computer using iTunes, including how to deauthorize all the computers you've used with your iTunes account.
Sign out of iCloud
If you use Find My Mac or other iCloud features on your Mac, you should first archive or make copies of your iCloud data.
After that, choose Apple Menu > System Preferences, click iCloud, and then deselect the Find My Mac checkbox.
Finally, sign out of iCloud. In System Preferences, click iCloud, and then click the Sign Out button.
When you sign out of iCloud, you're asked whether you want to remove iCloud data from your Mac. Your iCloud data will remain on any other devices that are using the same Apple ID.
See if you've registered your computer with Apple Support
Sign in to supportprofile.apple.com with your Apple ID and remove the computer if you see it listed there.
Sign out of iMessage
If you're using OS X Mountain Lion or later, sign out of iMessage.
In the Messages app, choose Preferences > Accounts. Select your iMessage account, then click Sign Out.
Erase and reinstall OS X
To reformat your hard drive and reinstall OS X, follow these instructions.
After you reformat your hard drive and reinstall OS X, the computer restarts to a Welcome screen and asks you to choose a country or region. If you want to leave the Mac in an out-of-box state, don't continue with the setup of your system. Instead, press Command-Q to shut down the Mac. When the new owner turns on the Mac, the Setup Assistant will guide them through the setup process.
Last Modified: Dec 9, 2015