Downloading and installing a new OS gives you the opportunity to do some major house cleaning if you so desire. If you feel like you'd like a fresh start with macOS Mojave, you can always opt to do a clean install: Just follow the steps below, even if you've already installed macOS Mojave. Make sure you understand the before you get started. Note: If you are reading this article on the Mac you want to perform the clean install with, switch to another device or print this page before continuing so you can read along as you go. Step 1: Back up your Mac This process will erase whichever OS you're currently using from your hard drive entirely. That means any files, programs, or documents you have will be deleted.
Jump to Format External Hard Drive for Mac - External Hard drives should be formatted before you use them as a Time Machine backup disk. If your Mac has High Sierra or an older version, differences may exist, but the process should look similar to what’s displayed below. Step 1: Connect your external hard drive. First, use the USB cable (or USC-C cable if you’re on a newest Mac model with Thunderbolt 3 ports) that comes with your external drive to connect that drive to your Mac.
To save your files, put them on an external hard drive or a cloud-based program like Dropbox, OneDrive, or iCloud. If you don't save these important files off your computer, you will lose them. Step 2: Create a bootable drive of macOS Mojave Before you erase your current operating system, download macOS Mojave from the Mac App Store. You'll need a copy of macOS Mojave to perform a clean install later on. If you don't create a bootable drive for macOS Mojave, you may have to install an older Mac operating system first and then upgrade to macOS Mojave afterward. Step 3: Erase your hard drive. Connect your Mac to the internet via Wi-Fi or Ethernet.
Click on the Apple icon. Select Restart from the drop-down menu. Hold down Command-R when you hear the startup chime (or the screen turns black on newer Macs) and keep holding the keys until your computer reboots. Click on Disk Utility in the OS X Utilities selector. Click Continue. Select your Startup Disk. Click on the Erase tab at the top of the window.
Enter a name for the file to be destroyed (Like macOS Mojave or something). If your Mac is using HFS+, select Mac OS Extended (Journaled) from the format list.
If your Mac is using APFS, select APFS from the format list. If Scheme is available, select GUID Partition Map. Click Erase. Step 4: Reinstall a new copy of macOS Mojave.
Click on Reinstall a new copy of macOS. Click Continue. Click Continue again when the installer window appears. Agree to the software terms and conditions. Select your hard drive. Click Install.
Complete the installation process. Any questions about performing a clean install?
Let us know below in the comments. Updated September 2018: Updated for macOS Mojave's public release.
With the launch of Apple's new Mac operating System, MacOS High Sierra, Apple has introduced a new file system called APFS. Standing for Apple File System, the new file format offers a much quicker experience that is designed for future growth and brings the MacOS operating system in line with the same file system that is the backbone of iOS. Installing High Sierra on your Mac automatically makes the change for you on your main hard drive, be it your MacBook or iMac, but it won't convert any external drives you have connected to the computer. You have to opt to do that yourself, and for good reason. Converting your external drives to APFS will give you all the same benefits you get from converting your main drive and will mean faster copying and duplication, better partition management, and native encryption, amongst other things.
See external hard drives on - You can convert all your external hard drives, regardless of whether they are solid state or not, via Apple's Disk Utility app. Open Disk Utility (command+space to launch Spotlight then type Disk Utility), then select the drive you want to convert. Go to Edit in the menu bar, and click on 'Convert to APFS'. The process, depending on the size of your drive, will take only a couple of minutes, and once complete, the external drive will be running on the new APFS format. There is a catch though. Converting your hard drive to APFS means it won't be able to be read by Macs or PCs not running APFS drives, which is any computer that isn't running MacOS High Sierra.
High Sierra is able to run on all iMacs and MacBooks launched after 2009. If you only use your external hard drive in your home with your own Macs that are all running High Sierra it won't be a problem, if however, you use that drive to share with other computers that you know won't have upgraded to High Sierra, it won't work. The drive will be unreadable to everyone but you and your High Sierra running machine.