Help! macOS Sierra won't install on my Mac!

20 September 2016, 04:15

macOS Sierra has landed and, with depressing regularity, it’s time for all those forum postings requesting urgent help. Perhaps the macOS Sierra install process gets stuck halfway through, or maybe Sierra appears to install but then won’t boot to the desktop. Maybe you can only boot to a cryptic screen full of text that’s faintly reminiscent of Linux.

What’s to be done?

Before you install!
Even before you install, if it’s not too late, undertake the following steps:

• Watch out for issues caused by SIMBL, which is an operating system plugin that lets certain apps hack system components to add extra functionality – see below;
• Update to the latest version of all your apps. If the app came via the Mac App Store this is easy – just open the App Store and click the Updates button. For other apps, you’ll have to start them and then click their Update menu entry, which is usually in the application’s main menu, or under its Help menu;
• Use Disk Utility to perform First Aid on your disk to ensure everything’s hunky dory – just tap the boot disk’s main heading in the list on the left and then tap the First Aid button;
  
  
• Backup your system. Seriously. Do it now. Don’t install macOS Sierra until you’ve done so. If you don’t normally backup, attach a hard disk via USB (they’re incredibly cheap nowadays) and use Time Machine, which is reliable and comprehensive. My quick and easy tip will significantly speed-up the initial backup;
• Create an emergency install USB stick of macOS Sierra, which will allow you to install from scratch on a system with a blank hard disk. To do this you’ll first need to download macOS Sierra via the App Store, but cancel the installation routine by selecting the quit option on the menu.

A partial list of apps that use the current popular incarnation of SIMBL, which is called EasySIMBL, are listed here. An older list of apps that use the older SIMBL is provided here. Take a look through the lists and check against your Applications listing. If your system is running one of the apps, uninstall it until after macOS Sierra has installed and then install the latest version of the app first ensuring it’s macOS Sierra compatible.

Before installing macOS Sierra you should also remove EasySIMBL or SIMBL if they’re installed, and then reinstall the latest versions once macOS Sierra has completed its installation, first ensuring they’re again macOS Sierra-compatible. To remove EasySIMBL, you should launch it within your Applications list, then uncheck the Use SIMBL box, and then quit EasySIMBL.app. Then move EasySIMBL.app to the Trash. A guide to removing the older SIMBL is provided here.

Help! macOS Sierra won’t install!
macOS Sierra can take a while to install so don’t give up if you’ve been waiting, say, up to an hour for it to complete. However, if it’s clear the installation has frozen, undertake a hard reboot – press and hold the power button until the computer powers down, before pressing it to power-up again – and hold down Shift as the Apple logo appears. This should boot you into Safe Mode, a process that clears various system caches. This might be a sufficient reparative step in itself, so try rebooting normally and see what happens.

No luck? Again reboot to safe mode and follow the instructions provided earlier to (a) remove apps that use SIMBL and (b) remove SIMBL or EasySIMBL. Reboot again.

Still stuck? Again reboot to safe mode and take a look in the following folders that contain startup apps and services. To visit each, open a Finder window then tap Shift+Cmd+G, and paste in one of the paths. Repeat for each of those listed. You might opt to temporarily copy the contents of each to a folder on your desktop and then possibly restore them once everything’s working:

~/Library/LaunchAgents/

/Library/LaunchAgents/

/Library/LaunchDaemons/

Also open System Preferences, click Users & Groups, select your username at the left, and then click the Login Items tab at the right. You might want to make a note of what’s there for future reference, but then select each in turn and click the minus button below. Note that the checkbox alongside does not control whether the app starts at boot up. It merely controls whether the app starts hidden. You need to delete the app from the list to remove it from startup.

If you reboot and still nothing is happening, try booting into recovery mode (hold down Cmd+R when the Apple logo appears) and then opt to reinstall OS X. This will possibly reinstall the previous version you had installed – probably El Capitan, for most of us – but at least it will leave you with a working system from which you can attempt to install macOS Sierra again after following the reparative steps mentioned at the top of this article. You can also opt to restore from your backup in recovery mode too.

macOS Sierra won’t boot!
If macOS Sierra completes installation but won’t subsequently boot to the desktop, the steps required to try and fix things are broadly similar to the steps above for a broken installation, although with particular reference to what apps and services are starting-up with macOS because it’s likely one of them is getting stuck – and taking the system with it.

If you just can’t get macOS Sierra to work, the nuclear option is a complete fresh installation via the USB stick mentioned earlier. This will involve wiping the disk. To do this insert the stick and hold down Option (Alt on some keyboards) to bring-up the boot menu, then select the USB option – it should be identifiable by the familiar USB logo. Select Disk Utility and opt to repartition your disk, then quit Disk Utility and select to install macOS Sierra.

Finally, keep an eye on my Twitter (@mackungfutips). I’ll be monitoring the usual forums to see if any issues crop-up with macOS Sierra, and will tweet about them as soon as possible.

Also check out our look at hidden features of macOS Sierra.

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