Before you upgrade

Before you begin to troubleshoot your existing High Sierra setup or install the system afresh, take time to spring clean your Mac. Get everything in order, then make a backup of your entire system using Time Machine or, better, a cloning app such as Carbon Copy Cloner (£35.88, bombich. com). As shown in last issue’s Detox and Back Up special, this means you’ll have a complete backup you can revert to if need be. (After you’ve installed High Sierra, ironically, Time Machine will automatically save a Local Snapshot of your system before installing any macOS update.) Even if High Sierra installs smoothly, people have reported various problems occurring afterwards, so you’ll be glad to have a backup from which to restore such vital data.

Verify your Mac can run High Sierra at bit.ly/abouthighsierra. Beyond the hardware needs, it must be running OS X 10.8 or newer. If it’s not, install El Capitan first (bit.ly/getelcap), and then upgrade directly to High Sierra: in the Mac App Store, click the Updates tab and you should see High Sierra in the list. If not, look in the Featured tab, or use the Search field at the top right to find it.

If you’re updating several Macs and don’t want to have to download the installer each time, it’s possible to create a bootable macOS installer on a USB flash drive or an external hard drive with at least 12GB of space. Any data already on this will be erased. You’ll need to use a Mac with High Sierra, Sierra 10.12.5, or El Capitan 10.11.6 or newer, with an internet connection to download the installer. Once downloaded, the installer will open automatically; press to quit it, then locate the Installer in the Applications folder. If you’re comfortable using Terminal, follow the steps Apple gives at bit.ly/create-installer.

Alternatively, try Install Disk Creator (free, macdaddy.io); in it, select the target USB drive, then the macOS installer, and click Create Installer. Eject the drive when it’s ready. To use it, connect it to the Mac you want to upgrade, restart the Mac and hold choose the install disk as the one to start up from, and the installer will run.

Downloading High Sierra adds an installer app to the Applications folder, from which you can make an install disk to use on multiple Macs.

When you click the Mac App Store’s Updates tab, it can take a while for available updates to appear. If you have multiple Macs on which to install a macOS update, download from support.apple.com instead.