Booting from external hard drive

angelsfan1 wrote:

I had to send my 2020 Macbook Pro in for service and it has been "on hold" for a week with no return in sight. I use my laptop for work everyday, and need to get things done. I have a Time Capsule with all of my time machine backups from my computer that is gone. I am trying to load these backups from another external drive that I copied all of my time machine backups to connected to my daughters MacBook Air. I have to do this because her computer does not have the storage of mine. When I try to boot from that external hard drive I setup, it is not showing up as a startup disk. Both computers running 12.4 Monterey. Have tried all I can think of. Any help anyone can think of?

Just because it is an external drive does not mean it is bootable.

Time Machine backup are bootable but is not going to run a macOS if that is what you are hoping.

Bootable backups¹ are more difficult these days since macOS Catalina.

you do not say if this Macbook Air you are trying to use is Intel or M1..(?) w̶h̶a̶t̶ ̶m̶a̶c̶O̶S̶(̶?̶)̶—I see 12.4

Security preferences do not allow for external boot unless changes are made in the more recent macOS

About Startup Security Utility on a Mac with the Apple T2 ...

If your Mac starts up to Options with a gear icon M1 - Apple Support

1. bootable backups ref:

https://bombich.com/blog/2021/05/19/beyond-bootable-backups-adapting-recovery-strategies-evolving-platform

https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html

How To Install macOS On An External Drive - Macworld

In order to boot from and external drive, you have to first install the OS onto the drive, then you select the external as startup.

https://www.macworld.com/article/672585/how-to-install-macos-on-an-external-drive.html

Time Machine backups will contain a bootable portion, but only in order to access the functions that one can get with MacOS Recovery.

It has to be restored to Mac in order to be bootable, although there may be flexibility in what version of MacOS is used. The only way to boot from an external volume is to install MacOS on it, or to create a bootable clone, such as with SuperDuper or Carbon Copy Cloner. I believe Disk Utility can create a bootable clone, but it's rather clunky and doesn't do things such as scheduled backups, incremental backups, or archiving deleted files. Time Machine does incremental backups (where only things that changed are copied over to the backup) but doesn't create a bootable volume.