What Is A Bootable File
What Is No Bootable Device

My mac option wasn't there! It only said windows. So from there I ejected the windows disk and now when I start up my computer it says 'No bootable device - inster boot disk and press any key'. Downloaded.dmg file on Mac, run and install. This one refuses to run the file. I downloaded TransMac on my other PC and made the USB bootable from that, using the same.dmg file that worked previously. The only other solution that i can thin of is to put this HD into the other Mac and try to install it there.

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. If in doubt, use the same Mac to reinstall macOS on that disk.

Settlers 2 for 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

What Is A Bootable File

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.

Make sure your display resolution in System Preferences is set to its default. Update samsung monitor driver. If the display turns off when you change resolutions, press the escape key to undo the change.If you can't change the resolution of your display because you can't see an image, restart your Mac in to reset the display resolution to defaults.If starting in safe mode doesn't resolve the issue, reset your Mac's and to reset the video ports on your Mac to their defaults.

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.

What Is No Bootable Device

If you're using a firmware password, the ability to load Option ROM firmware is disabled as an additional security protection. Galileos viewer for mac.

What Is A Bootable Device For Mac