Bootable Mojave doesn't appear as choice on external start up disc

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Bootable Mojave doesn't appear as choice on external start up disc

Dear All,

It seems that I have successfully created an external hard drive containing Mojave bootable media, or so Terminal tells me, but when I try to boot from that external Mojave drive, it does not appear in the selections menu --only Catalina appears after I hold down the option key and try to start from Mojave. What am I doing wrong, or is Catalina muddying the waters. Catalina will not allow me to install Mojave directly because it says the installation disc is too old, so I have to go through Terminal. It erases the external hard drive completely and creates a bootable Mojave,, but I'm wondering if that's the problem -- it is no longer formatted as a journaled disc, but as an installation disc. How can I overcome these problems? Thanks.

Posted on Oct 17, 2019 12:56 PM

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Answer 1

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Barbara Smits Author

Level 2

277 points

Oct 17, 2019 5:55 PM in response to den.thed

In another discussion, I found that my Mojave startup disc was not partitioned to GUID, and that was why I was not seeing it. They told me to go to the View menu and view the external drives there, and I was then able to format it to GUID. It now appears in my startup disc selection window after installing Mojave to it. Now that I can choose it as as startup disc, I hope that it works! Thanks to all who helped! Barbara Smits

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Answer 2

den.thed

Level 10

83,230 points

Oct 17, 2019 1:14 PM in response to Barbara Smits

If your objective is to go back to Mojave? Then you will need to startup in macOS Recovery and erase the Catalina containers, then you should be able to startup from the Mojave installer, reformat the drive and install 10.14.

LOL yup' muddy water is a good way of put-nit.

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Answer 3

Barbara Smits Author

Level 2

277 points

Oct 17, 2019 2:27 PM in response to den.thed

No, I do not want to go back to Mojave -- I just want to be able to boot from Mojave to use a few selected software programs that don't run on Catalina. Booting from Mojave installed on an external drive seems to be a viable option, but Catalina isn't recognizing that option. The only choice they give me is Catalina and a menu of networking drives that do not pertain. So, the water is indeed muddy, but I don't know how to clear it up! Thanks for trying!

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Answer 4

den.thed

Level 10

83,230 points

Oct 17, 2019 4:59 PM in response to Barbara Smits

I know it works because I'm doing it.

At this point, I would suspect that there is something wrong with the formatting or the Mojave installation and would test the on another Mac to see if it is actually a valid startup disk.

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Answer 5

Barbara Smits Author

Level 2

277 points

Oct 18, 2019 5:56 AM in response to den.thed

Dear All,

Even though it now appears, it still isn't working. Rather than starting up in Mojave, selecting the external drive as the startup system just opens up disc utility, which give me a choice of four options, none of which I want to deal with. So, it's back to the drawing board to figure out what's happening. Folks in the other forum, and I, think that the wording used in Terminal has created an installation disc rather than a boot disc, even though it tells me that it's a boot disc. I hope that we can figure it out!

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Answer 6

Barbara Smits Author

Level 2

277 points

Oct 18, 2019 11:36 AM in response to den.thed

Dear All,

That sounds great, but when you try to open the downloaded Mojave application and install it, Catalina gives out an error message "This copy of the “Install macOS” application is too old to be opened on this version of macOS", so the install download cannot be opened. You have to go through Terminal language to install it, and even though it reads that you have successfully created boot media files on the external hard drive, that does not work. I have gone to my local Mac dealer where I bought the computer, and they are going to create a bootable disc for me...I hope! Good luck!

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Answer 7

den.thed

Level 10

83,230 points

Oct 17, 2019 3:02 PM in response to Barbara Smits

Ah... I would Format and Install macOS Mojave on an External USB 3.0 drive, then I would Restart and use the Startup Manager to select the Startup Disk.

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