In the following instructions, we will use a USB flash drive as an external carrier example. Give your disk the name of the operating system, e.g., Sierra, Mojave, Catalina.

Whichever type of drive you choose, make sure that it has at least 12GB of free memory.īear in mind-when you download an installer, the disk will be reformatted to suit the operating system you’re trying to run.

Use Terminal to create a bootable installerįor your external disk to run macOS, you can choose as a USB flash drive, as well as an SSD or HDD.

In this article, you’ll find detailed instructions and answers to your questions on how to make a bootable USB on Mac. You can try out the different tools for free, so download it, and see what you think. MacKeeper can do everything from finding malware to updating your apps for you.

When the scan is finished, review the results, and click Fix items safely.

Select Find & Fix from the menu in MacKeeper.

You can do that with MacKeeper’s Find & Fix feature, which will scan your Mac for a variety of different problems. It’s a good idea to keep your Mac optimised when you’re asking to create a bootable USB drive. It’s a handy appliance-even more so if you use a small external flash drive that you can carry in a pocket. You can also use it to reinstall the operating system on a Mac that won’t startup. Such a tool allows you to install any version of macOS on multiple Apple computers easily. Why would you want to create an external boot drive for your Mac? Neither one had any issues.A bootable macOS (previously, OS X) install disk is a portable device containing all the necessary installation files for a selected version of macOS. So I quit Startup Disk and went back to Disk Utility, and I tried running First Aid on both Macintosh HD and OS X Base System. Startup Disk could not gather enough information on the selected disk.

You can’t change the startup disk to the selected disk. Clicking restart, as one might expect, yields the following error message: So I thought I’d try quitting OS X Utilities without reinstalling OS X and see what happens.Īfter clicking on Choose Startup Disk, I get a blank list to choose from, with a restart button. But when I hit continue, it gives me an error message:Īn error occurred while preparing the installation. I restarted with cmd R to load OSX Utilities, and I used Disk Utility to wipe Macintosh HD, overwriting it three times and formatted as OS X Extended (Journaled).Īfterwards, after successfully connecting to my Wi-Fi, I clicked on Reinstall OS X, and it’s giving me the option to set up El Capitan (the OS X that’s installed, and from what I can tell, the latest that can be installed). I’m helping someone with their old laptop (17”, mid-2009, if that matters).

Os x boot disk utility