I use an external HD with Time Machine to back up data.
Should I disconnect external HD before installing/upgrading to El Capitan?

  • Welcome to Ask Different. By backing up, do you mean with Time Machine?
    – bjbk
    Oct 31, 2015 at 1:36
  • yes (time machine)
    – user155131
    Oct 31, 2015 at 2:15

2 Answers 2


Quick answer: No, you shouldn't have to, as long as you don't select to install to it during the upgrade process. It shouldn't hurt to disconnect it though, if you want to.

  • I would recommend doing it. If something goes wrong, it's better to be safe then sorry.
    – At0mic
    Oct 31, 2015 at 3:18
  • Of course, always air on the side of caution (unless you like learning things the hard way).
    – Daniel
    Oct 31, 2015 at 4:57

For full belt & braces backup protection, I always remove my Time Machine drive right before a major update & replace it with a new one.

That way, if you have major issues with the new OS - incompatible drivers with no updates yet, etc - you have a 'restore point' to return to.

I also make a clone of the boot partition & I have a full Backblaze backup of everything too.
You might consider that paranoid overkill, but I haven't lost a file since the mid 90's ;-)

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