When you set a startup disk information is saved in the NVRAM on the machine and during power on this data is retrieved.

If you used Disk Utility from macOS Recovery, you can now restart your Mac: choose Apple menu  > Restart. Answer (1 of 3): The startup disk is configured via the System Preferences (Startup Disk). The order of repair in this example was Macintosh HD - Data, then Macintosh HD, then Container disk4, then APPLE SSD. Keep moving up the list, running First Aid for each volume on the disk, then each container on the disk, then finally the disk itself. If you're asked for a password to unlock the disk, enter your administrator password.Īfter Disk Utility is done checking the volume, select the next item above it in the sidebar, then run First Aid again.If the button is dimmed and you can't click it, skip this step for the disk, container, or volume you selected.If there is no Run button, click the Repair Disk button instead.In this example, the last volume on the disk is Macintosh HD - Data.Ĭlick Run to begin checking the selected volume for errors. Neither one had any issues.For each disk that you're repairing, start by selecting the last volume on that disk, then click the First Aid button or tab. 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. After you reinstall, open Terminal and write a shell command to use the Unix setregproptool (its inside the firmware password utility.app contents located in the installer image and also on the recovery partition) and remove the password by calling the remove password command. 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). Then start disk.app and change to the USB, then reinstall OS X. I’m helping someone with their old laptop (17”, mid-2009, if that matters).

How to clear startup disk on mac air