Upgrade OS on external drive - is it possible?

[cltd]

Hello,
I have external drive with full bootable OS backup (Yosemite). I can boot Macbook from this drive. Is it possible to set this drive as startup disk, then upgrade it to Mojave? I'm afraid of startups during upgrading - how it will go with external drive.
Thanks for any experience.

 

[Dave Braine]

Yes, perfectly possible. It may just be a little slow.

 

[cltd]

Thank You for answer. Of course, should be "afraid of reboots", not "startups".

 

[appltech]

Hello,
I have external drive with full bootable OS backup (Yosemite). I can boot Macbook from this drive. Is it possible to set this drive as startup disk, then upgrade it to Mojave? I'm afraid of startups during upgrading - how it will go with external drive.
Thanks for any experience.

You can definitely install a MacOS update on an external drive. I’m assuming you need this to test a new version of the OS or to run a beta version. It’s a good way to peek into an OS without the risk of messing up your Mac.
As said earlier, it might be rather slow, so I suggest getting a good cable and a drive that eats less power. You’ll need at least 12GB of storage on the disk to install an OS. Then you can do the following:

1. Connect your drive to the Mac device and launch Disk Utility;
2. Choose your disk under the “External” heading in the sidebar on the left side of the window;
3. Click on Erase in the menu bar at the top of the window - make sure any important data is backed up before you use it;
4. Choose the format “OS X Extended (Journaled) and the scheme “GUID Partition Map”;
5. Name the drive and finish the setup;
6. Go to App Store and look for the link to the latest version of the OS on the right side of the screen. Download the Installer;
7. Open the Installer. You’ll eventually reach a window that will ask you which disk you want to install the OS on. It should be set on Macbook, but if you click on “Show All Disks” you will be able to choose your external hard drive;
8. Click “Continue” and complete the installation.

Hope this helps!