Catalina on An External Hard Drive

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Catalina on An External Hard Drive

Upgrading from Sierra on my Late 2013 27" iMac. Added Catalina OS on an EHD. Everything seems OK. However looking at the EHD it appears that the OS is divided into 2 partitions on that EHD. Is this to be expected?

Regarding apps and programs on my Sierra, I know some won't work on Catalina. However how can I transfer the workable apps and programs without losing them and their function on Sierra? I don't want to loose the function on Sierra and yet have it available on Catalina.

I also have my photos and music libraries on EHDs, not the main computer hard drive. How can I use the libraries on either/both OSs from that one source library?

Thanks for your help.

iMac Line (2012 and Later)

Posted on Nov 17, 2020 4:49 PM

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ryane77

Community Specialist

Nov 25, 2020 3:23 PM in response to elkriverken

Hi elkriverken,

Thanks for the post in Apple Support Communities. It looks like you might have a few questions about running macOS Sierra on your internal drive and macOS Catalina on an external drive. We'd be glad to see if we can provide some answers.

Regarding the two partitions, yes, that is normal. Check out this link for more: About the read-only system volume in macOS Catalina

When it comes to moving apps, your best bet would likely be to download macOS Catalina compatible versions while booted to the external drive; copying macOS Sierra versions of software directly to macOS Catalina could result in compatibility or permissions issues, but downloading them would ensure they are the correct versions for macOS Catalina.

Also, you mentioned accessing Photos and Music libraries that are also on external drives. These are separate external drives from the one you're using for macOS Catalina, correct? It sounds like it may be safest to consider something like this since macOS Sierra runs iTunes, while macOS Catalina is going to be running the Music app: Set up media sharing on Mac. As a side note, before making any changes to media libraries in this type of situation, it may be good to ensure you have a backup of it.

We hope that helps! Take care.

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Catalina on An External Hard Drive

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