Safely shift data from old to new Mac

[AMSOS]

I am going to order an Air (it'll likely have High Sierra or Mojave) and sell my old Mac (Sierra) and for that I need to make sure that I transfer my data safely.

I am planning to first buy the new Air, and use AirDrop to shift files to my new computer.

1) At what stage should I sign out of iCloud on my old Mac? Should I first sign-in and setup iCloud on my new Air and then sign-out of iCloud on the old Mac? Or the other way round?

2) Once that is done I'll need to erase the old computer before I sell it off. How exactly should I do this?

3) I have regular TimeMachine backups from the old Mac. Do I need to setup the ext. HDD for the new Mac or will it automatically start adding backups from the new Mac to the ones it already has?

Thanks!

 

[Brian33]

I would use Migration Assistant. I would think a new Mac would prompt you to use it during the initial setup. It will copy all the typical stuff (apps, user accounts, documents, settings, etc.) from the old Mac to the new one. Then go look for any files you might have put somewhere other than the /Users directory and transfer them yourself.

I would stay logged into icloud on the old computer, and would log in to icloud on the new one when prompted. There's no harm being logged into icloud on two different computers (I'm logged in on three Macs right now).

Before erasing the old computer, log out of icloud. Also, go into iTunes and de-authorize the computer if you've authorized it to play iTunes content for your Apple ID in the past. Apple remembers these "authorized" devices and there's a limit of five. (Although it's not critical -- if you forget to do it before erasing the old computer you can de-authorize all computers, and then re-authorize any you still want.)

I believe Time Machine on the new Mac will start a new backup series (copying everything on the new Mac) while leaving the old one on the disk. The safest thing to do is to erase the old backup set only after migration is complete and you are sure you won't need anything from the old computer's backup. This could be quite some time, and could be a bit of a problem if the disk isn't big enough for both backup sets.

Good luck with your new Air!