Reinstall macOS

If you need to take the extreme step of reinstalling macOS Sierra, you can do so using Recovery mode. You can choose to erase the drive and start fresh, or simply replace macOS and leave your documents and apps alone. This is handy for fixing extreme problems or before passing the Mac along to a family member.

Video Transcript
So yesterday I showed you how to take a Mac and restore it to a clean new state just like you bought it from the store using internet recovery mode. That restores it to the operating system that you had when you originally bought the machine.

However you may not want to do that. You may actually want to restart a Mac, set it new, but keep the current operating system maybe just to start off fresh or hand it off to somebody else in your family. It's a lot easier to do that.

The way to do that, of course, is to restart it into recovery mode, not internet recovery mode which is Option Command R but regular recovery mode which is just Command R.

So I'm going to do a restart here and as soon as I start the restart I'm going to hold down Command and R. Then it's going to start up in recovery mode. Now I can release and I should see it move much quicker. It took about twenty minutes to do internet recovery mode because it had to load the entire recovery partition from the internet but recovery mode is actually loading a special version of the operating system that's on a hidden part of your hard drive. So it doesn't actually have to contact the internet to do this. It loads in pretty quickly.

So now you're in Utilities and if you watched yesterday's video you can see this looks a little different and it says MacOS Utilities because this is the Sierra version of that. It's using the latest version that I have on this machine rather than the original operating system version which is what happens if you do internet recovery.

If I wanted to clear off this Mac I could go into disk utility here. Once I'm in disk utility I can select the drive. You can see here's, under disk images, here is the recovery partition I'm currently using. It's very small. It's only about 2G big. Here is the Macintosh hard drive. You can see that's the full drive there. I can use Erase and I want to erase and probably keep the name, Mackintosh hard drive, I want to do MacOS Extended and Journaled, and hit Erase.

So now you can see it's done. Hit Done. Now I've got an empty drive. You can see nothing is used. I Quit disk utility here.

Now I need to reinstall MacOS because there's nothing on that drive. So there's nothing you can do. You can't boot normally. You have to only to be able to boot into this recovery partition. If I wanted to, if I had a time machine backup and I was using this to restore my machine I could do it from a time machine backup.

I'm going to do Reinstall MacOS. Hit Continue. Then it's going to walk me through the process. I'm going to select the drive. Hit Install. It will download and install a fresh copy of Sierra on this Mac.

So once it's all done you end up with the Welcome screen here. You can start setting up. If your plan is to give this Mac to somebody else you may want them to set it up instead of you doing it for them. You can do that by simply using Command Q to quit and you get the option to shut down and then basically when they start it up they end up right back on this screen where they can set up the Mac to use for themselves with their own user account and everything.

Comments: 19 Responses to “Reinstall macOS”

    Patrick Davies
    12/8/16 @ 1:35 pm

    Thanks, Gary, great video as always. I may be selling my MacBook Air to my neighbour and it would be nice to have the latest OS on the laptop rather than the original factory installed OS. As long as I delete all my accounts, is there any reason why I can’t go for this option rather than the one outlined in yesterday’s video which used internet recovery?

    12/8/16 @ 1:39 pm

    Patrick: If you install the latest OS, or leave it on there, it will be registered to YOU. The “download” for the OS will be under your name and Apple ID. This will cause him trouble (and maybe you too). Best to roll it back to the original OS. Then he can log in and do the upgrade to Sierra right away. You can help him with that if you want.

    Michael Simms
    12/8/16 @ 3:31 pm

    Why not use an install disk created from macOS Sierra install program??

    12/8/16 @ 3:37 pm

    Michael: Disk? Macs don’t come with optical disc drives anymore.

    12/8/16 @ 5:46 pm

    Love those vids Gary! I have a question though, what if I download Sierra from the App Store using My Apple ID then create an installer USB flashdrive from that Mac OS, will this installer register under my apple id on any mac I install it on? (I did this to one of my mac mini’s which I already sold).

    12/8/16 @ 6:01 pm

    Nassar: Not sure, sorry. I would assume so, but I can’t say without trying it.

    12/8/16 @ 6:07 pm

    Gary, did I muss the part about reinstalling the os while leaving your files & apps intact?

    12/8/16 @ 6:52 pm

    rhkennerly: If you just reinstall the OS, then that is what you get. So DON’T do the erase the disk part. And, as always, back up first.

    12/8/16 @ 8:48 pm

    What if I try doing it on like a random mac. How would I know or check if my Apple ID is registered to the OS?

    Thanks alot.

    12/8/16 @ 9:38 pm

    Nassar: Not sure. Hard to test. I don’t think it will, but I can’t find any source that says either way.

    12/9/16 @ 10:45 am

    If I install a new macOS Sierra to my old 2011 MacBook Pro and clean out as a new computer, will all on the install app’s be downloaded with the install? As, launchpad, Siri, Safari, App Store,ibooks, FaceTime, etc?

    12/9/16 @ 11:00 am

    Lee: Those “apps” you mention are part of macOS (Siri, Launchpad, Safari, App Store, iBooks, FaceTime). Other apps, like iMovie, Pages, etc, are separate apps. If you clean the drive and just install Sierra, you will only get Sierra (which includes those apps I mentioned). Other apps, like iMovie, you would simply download again from the App Store once you are done installing Sierra.

    12/9/16 @ 2:08 pm

    Gary, my 5yr old i5 16Gb iMac is significantly slower than when I got it. Very slow when you login or switch users (can literally take 2 minutes before it becomes fully responsive). I’ve got plenty of disc space left – would doing a reinstall without erasing my files and apps help? Or is there other things I should be looking at?

    12/9/16 @ 2:11 pm

    Glynne: You should take it to an expert (Genius Bar) if you can’t diagnose it yourself. Reinstall may not help, or may only be a temporary help. Better to find out what is really going on.

    12/10/16 @ 7:46 pm

    Hi Gary, would like to do that but unfortunately NZ doesn’t have an Apple Store yet. I think I’ll try a reinstall and see what happens.

    12/11/16 @ 12:29 am

    Now I’m REALLY confused. How many operating systems for MACs are there?

    12/11/16 @ 7:49 am

    Squafdonoboles: Not sure what you mean by that question. Every year Apple comes out with a new version and gives it a name. The current one is 10.12 and is called Sierra. Before that we had El Capitan (10.11), Yosemite (10.10), Mavericks (10.9), etc. Each one has brought new features to OS X (now called macOS).

    Nick Moye
    12/14/16 @ 11:06 am

    I have an older macbook that has OS X 10.6.8 I want to reinstall OS only, not a complete install. I didn’t see any video on how to do this with my current OS.
    Can you please show/tell me how to do this? My current problem is that the beach ball shows up almost as soon as I get to main screen and just will not stop.. Have tried Apple tech and they say it’s to old to work on…

    12/14/16 @ 11:35 am

    If your Mac is old enough to have an optical drive and use Snow Leopard (10.6) then you would do the reinstall by booting from the Snow Leopard disc.

Comments Closed.