Macbook air clean install issue

You have two things going on here. You can't erase the entire drive because you are booted to the recovery partition on that drive. Also, secure erase is greyed out on SSDs because it harms the SSD.

If you just do a simple erase on a SSD it is very difficult for anybody to recover that data. It you are still concerned and want to make doubly sure nobody can recover data do this... login to your account and in the Security pane turn on Filevault full disk encryption and wait for it to finish encrypting.

Now do a command-option-r (all three keys at once) boot to Internet recovery. Once the recovery screen comes up start Disk Util and you can now select the entire disk at the top to erase. This works because you are now running off Internet recovery and not the SSD recovery partition.

Once the erase is done just click install OS and wait for it to finish.

What you have done is encrypted your data then erased it. So even if somebody managed to restore some data it would be encrypted and not accessible.

Serban said:

so for an imac with fusion drive should i go with internet recovery and erase the entire HDD? i will give to an apple reseller store (buyback) for the new 27" haswell.

Click to expand...

That is all I would do. Like I say... if you are SUPER concerned about something private on there you can encrypt with Filevault first then erase.