I am not sure if there is any specific property of the drive or any specific file that can help me uniquely identify the internal boot drive. 'diskutil info ' command gives a 'Bootable' property of the slice, but that property is not good enough as that property is being returned as true for multiple slices of a single drive or for all the drives. Mar 12, 2020 After creating the bootable installer, follow these steps to use it. Plug the bootable installer into a compatible Mac.; Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it.
By default, your Mac starts up from its built-in hard disk, but a startup disk can be any storage device that contains an operating system compatible with your Mac. For example, if you install macOS on an internal or external drive, your Mac can recognize that drive as a startup disk. You can then follow the steps in this article to start up from it.
Use Startup Disk preferences
When you use Startup Disk preferences to select a startup disk, your Mac starts up from that disk until you choose a different one.
- Choose Apple menu > System Preferences, then click Startup Disk.
- Click the lock and enter your administrator password.
- Select your startup disk, then restart your Mac.
If you see a message that your security settings do not allow this Mac to use an external startup disk, check the External Boot setting in Startup Security Utility.
Use Startup Manager
When you use Startup Manager to select a startup disk, your Mac starts up from that disk once, then returns to using the disk selected in Startup Disk preferences.
- Press and hold the Option (Alt) key immediately after turning on or restarting your Mac.
- Release the Option key when you see the Startup Manager window.
If your Mac is protected by a firmware password, you can release the key when you're asked to enter the password. - Select your startup disk, then click the arrow under its icon, or press Return.
If you press and hold the Control key during this step, your selection is saved in Startup Disk preferences, so it persists until you change it.
If your Mac is using OS X Lion 10.7.3 or later, you can also use this method to start up from your Time Machine backup disk. Startup Manager identifies your Time Machine backup as ”EFI Boot.”
If you can't select your startup disk or start up from it
Check for these possibilities if you can't see your disk in Startup Disk preferences or Startup Manager, or your Mac won't start up from it.
Check for a compatible operating system on the startup disk
Make sure that your startup disk is using a version of macOS that is compatible with your Mac.
To start up from an external disk with macOS Catalina 10.15 or later, the disk must connect via USB-A, USB-C, or Thunderbolt, not FireWire.
Check startup security settings
If you're using a Mac that has the Apple T2 Security Chip, check the settings in Startup Security Utility. These settings determine whether your Mac can start up from another disk.
Check for Option ROM firmware
If you're in Startup Manager and can't see a third-party startup disk, the startup disk could be using Option ROM firmware. To enhance system security, Mac computers with up-to-date software don’t show devices that use Option ROM firmware until you load their firmware. To do that, press Option-Shift-Command-Period while in Startup Manager. If your startup disk appears, do that each time you want to start up from it or from another disk connected to it.
If you're using a firmware password, the ability to load Option ROM firmware is disabled as an additional security protection.
In theory, you should have to install Mountain Lion only once, or never if your Mac came with Mountain Lion preinstalled. And in a perfect world, that would be the case. But you might find occasions when you have to install/reinstall it, such as
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If you get a Mac that didn’t come with OS X Mountain Lion preinstalled
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If you have a catastrophic hard-drive crash that requires you to initialize (format) or replace your boot drive
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If you buy an external hard drive and want it to be capable of being your Mac’s startup disk (that is, a bootable disk)
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If you replace your internal hard drive with a larger, faster, or solid state drive
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If any essential OS X files become damaged or corrupted, or are deleted or renamed
The following instructions do double duty: They’re what you do to install OS X for the first time on a Mac, and they’re also what you do if something really bad happens to the copy of OS X that you boot your Mac from. The instructions offered here describe both the process for installing and the process for reinstalling OS X.
Here’s how to install (or reinstall) OS X, step by step:
Mac Os Replace Boot Drive Internal Mac
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Boot from your Recovery HD partition by restarting your Mac while holding down the cmd+R keys.The OS X Utilities window appears. Select Reinstall OS X, and click Continue. The OS X Mountain Lion splash screen appears. Click Continue.A sheet appears informing you that your computer’s eligibility needs to be verified by Apple. Click Continue to begin the process of installing or reinstalling OS X.If you’re not connected to the Internet, you’ll be asked to choose a Wi-Fi network from the AirPort menu in the top-right corner.
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The Mountain Lion software license agreement screen appears. Read it and click Agree.A sheet drops down, asking whether you agree to the terms of the license agreement. Yes, you did just click Agree; this time you’re being asked to confirm that you indeed clicked the Agree button.If you don’t click Agree you can’t go any farther, so I advise you to click Agree now.
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Choose the disk on which you want to reinstall OS X by clicking its icon once in the pane where you select a disk.If only one suitable disk is available you won’t have to choose; it will be selected for you automatically.Click the Install button.
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A sheet asks for your Apple ID and password. Type them in the appropriate fields; click Sign In, and your Mountain Lion installation (or reinstallation) begins.The operating system takes 30 to 60 minutes to install, so now might be a good time to take a coffee break. When the install is finished, your Mac restarts itself. If you were reinstalling OS X on a hard disk that it had been installed on previously, you’re done.Your Mac will reboot and you can begin using your new, freshly installed (and ideally trouble-free) copy of OS X Mountain Lion.If you’re installing Mountain Lion on a hard disk for the first time, however, you still have one last step to complete. After your Mac reboots, the Setup Assistant window appears. You need to work your way through the Setup Assistant’s screens.