Q: How to prepare a macbook pro for reselling

Hi,

I am going to sell my 2014 macbook pro with yosemite installed, but wanted to check 2 things.

1/ erase ssd

I want to "secure" erase the ssd and was thinking about doing it like so :

http://osxdaily.com/2013/04/22/secure-erase-mac-ssd-drive-recovery-mode/

summary :

- erase the disk via recovery console and select "journaling with encryption"

- erase it again and now i can select the "number of erase-passes". 7-pass seems enough.

Questions :

- is this method "secure" enough for reselling ?

- any other consequences why i should not do this in the above way ?

2/ unlink between apple id and macbook

I suspect that there is some kind of link between my apple id and the machine, itunes, icloud, i-dontknowwhat,  etc etc

What i want to avoid is that, because of this link, some cloud-data (that is linked to the macbook) is synced back once the new owner is using it...

How can i make absolutely sure that this is not the case ?

A few weeks back, i already logged in with all my apple id's @ htpp://supportprofile.apple.com and one of the logins indeed showed a link to this machine.

I pressed the "unlink" button, but this unlinking had to be confirmed through a mailbox that i do not have access to anymore...

Yesterday, if i logged in again at the same website, the machine is not linked anymore (so without confirming the unlink !)...weird ?

Question :

- how did the unlink happen and how can i make sure that there is no link anymore ?

Thank you for your time and kind regards,

Tom.