MacOS – Updating to macOS Catalina gets stuck, when trying to update from OS X Mavericks

This happened earlier this year to a friend. The cause was disk directory damage. Upon start (during the Gray Screen of Doom) the Mac was trying to repair the damage automatically, but failing. Here's how I talked her through it.

1. Power down the Mac.

2. Boot in Safe Mode (press Power button, listen for startup tone, immediately press and hold Shift, release Shift when you see Apple logo).

3. Let the computer boot in Safe Mode. It may take longer than normal.

4. If the computer eventually reaches the desktop, simply reboot normally and see if that fixed your problem. This is the point at which this procedure worked out for my friend.

5. If the computer is still having problems, boot from a Mac OS X Install DVD (insert DVD, power down, restart hiding down C key).

6. When you reach the Installer screen, use the Utilities menu to run Disk Utility, then choose Repair Disk under the First Aid tab (if the hard disk doesn't show up in the sidebar in Disk Utility, the disk is likely irretrievably broken).

If these steps don't work, I'd suggest that you either a) Wipe the disk and do a full restore from your most recent backup; b) invest in a heavy-duty disk utility like Disk Warrior; c) take the computer to the nearest Apple Store for support help.

The only thing that may work for you is this (although, I wouldn't get your hopes up):

1. Start your computer and hold the ⌘ + S keys to get into Single User mode.

2. Once you're in Single User mode, type in unmount -uw / and press enter.

3. Now, type in fsck -fy and press enter. It should go through several stages of checking and repairing the file system.

It will most likely give you an error stating that it cannot be completed for some reason, but it's worth a shot.

Alternatively, if the issue is isolated to the file structure, you can try doing a reinstall of Mac OS X from the recovery partition. Doing just a reinstall should not erase any of your data.

However, you may want to try to back up your computer first. The only way that I can think of to do this on a MacBook Air 2011 is to use Thunderbolt target disk mode. This will require that you have access to another Thunderbolt equipped Mac as well as a Thunderbolt cable.

If you don't, I'd take a trip to the Genius Bar at your nearest Apple Store. They'll have the extra Mac and equipment necessary to do this. If they/you decide to do this while you wait at the Genius Bar, expect to be there for a couple hours just in case. If they/you decide to leave it with the Geniuses, there is a $99 data transfer fee that they'll most likely charge you.

The only other option is to:

1. Boot your Mac to the recovery partition

2. Open Disk Utility from the Utilities menu

3. Follow these steps to erase your SSD

4. Reinstall Lion on your MacBook Air