When trying to install MacOS on an external SSD, the internal SSD is always booted when restarting.

When I select the external SSD in the bootloader, it only shows that the installation is corrupt. In the MacOS installer there is an option to select the disk on which you want to install MacOS. I just selected the external SSD. There is also a menu on M1 macs where you can decide from which SSD you want to boot from. Just hold the power bottom for like 15 seconds until it shows up. You can also configure a standard startup disk in your MacOS system preferences or in the mentioned boot loader.

I watched some YouTube videos about it and it worked for them. They are able to install MacOS on multiple drives and select from which there wanna boot. I want to archive this to because of my work I need different installations.

Can anyone help me installing MacOS on a external drive? Do you think there is a solution or is this more of a Mac bug?

  • How did you install Mojave on the external disk?
    – nohillside
    Jan 21, 2022 at 20:31
  • 1
    Booting on an M1 mac is different and you need to look at M1 specific information e.g. eclecticlight.co/2020/12/22/… Note M1 will only run BigSur or Monterey.
    – mmmmmm
    Jan 22, 2022 at 10:00

1 Answer 1


Since your Mac is M1 be sure you are installing Big Sur or Monterey on the external drive first.

If you need older OS, you’ll have to use hardware that can run the older installers or work on virtualization / emulation modifications.

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