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Running Sierra on a late 2013 iMac. Loaded Catalina on a 1TB Crucial SSD EHD. No real problems switching between OSs. However on Disk Utility the Catalina volume is not on the Crucial EHD, but on Apple APFSMedia. And running First Aid doesn't work on either Catalina volumes. Is this or can this be a problem?
iMac Line (2012 and Later)
Hey again!
I’d probably recommend, after reformatting the EHD as HFS+ or Mac OS Extended (Journaled), to start with the installation of High Sierra, when the APFS format was introduced, and produced the natural conversion of the formatting, then, downloading any of the future OS’, Mojave and above, etc.
I cant say why exactly, but have seen problems jumping from formats from before High Sierra to after High Sierra, but not in between.
However I’ve also seen different brands of EHD’s react differently whether they are SSD or HDD. And of course the state of the Mac they are connected to is a factor. But regarding the formatting, those are my thoughts, hope that helps!
Hey again!
I’d probably recommend, after reformatting the EHD as HFS+ or Mac OS Extended (Journaled), to start with the installation of High Sierra, when the APFS format was introduced, and produced the natural conversion of the formatting, then, downloading any of the future OS’, Mojave and above, etc.
I cant say why exactly, but have seen problems jumping from formats from before High Sierra to after High Sierra, but not in between.
However I’ve also seen different brands of EHD’s react differently whether they are SSD or HDD. And of course the state of the Mac they are connected to is a factor. But regarding the formatting, those are my thoughts, hope that helps!
i too needed a separate external drive with catalina installed on it. i have some hardware that's incompatible with big sur. and the vendor has no plans to update past catalina. so when i did that, i followed the well written and very informative user tip from Jack-19.
How to Setup and Use an External SSD as your Startup Disk - User Tip
Changes since my request. I will be as specific as possible.
Catalina OS, macOS 10.15.7.
Unlocked, chose Catalina OS, and restarted. "You have selected macOS, 10.15.7".
Restarted, but on Sierra, macOS 10.12.6, NOT Catalina. And Sierra is still OK.
What is my problem? What is the solution?
Thank you.
Hey elkriverken!
So can you clarify the question?
You said you do have Catalina running on the external drive, and Sierra on the internal drive.
When looking at Disk Utility, which drive are you booted from? And how are you discerning what OS is on it? (Because the APFS format)?
If running First Aid on a startup disk, you should either be in recovery mode, or booted up from a different startup volume than the one you need to run First Aid on.
Likewise, if you startup your Mac to OS Recovery, (Start up holding Command R), what do you see in Disk Utility there?
Can I ask the reason for running First Aid in the first place? (Maybe related).
Thanks, happy to help out if I can.
I decided to erase the EHD and start all over again. Now during installation of Catalina on the Crucial reformatted EHD, it only downloads Catalina OS and NOT Catalina OS - Data. And on using System Preferences > Startup Disk, the Catalina OS doesn't show up.
Any help is appreciated. Thank you.
i should add that catalina was the macOS that my mac shipped with. to get catalina in recovery on my mac, i needed to start recovery with the keyboard shortcut "shift + option + Command + R". then i was able to install catalina on the external SSD.
After following all the recommendations to load Catalina on my SSD EHD, continued failure to pick it up as a startup source.
So I decided to restart my process: after treating the SSD via Disk Utility with First Aid, reformatting, now tried installing Mojave, with the same results. The download and installation went as expected, but my Sierra did not show Mojave as a startup disk.
After erasing, first aid and reformatting the SSD, used it to backup my music files. Had no problems, a successful backup.
Conclusion: The SSD was OK as a backup, but not as a startup OS EHD.
Any comments are appreciated.
I was able to reformat the SSD, download the High Sierra from App Store. I then installed High Sierra on the SSD.
To System Preferences > Startup Disk. Only the IHD Sierra and it's eDrive were there. No High Sierra.
In Applications, the Install High Sierra remained.
When I opened High Sierra from the sidebar in Applications, it contained MacOS Install Data, 12 items.
Essentially my results with Mojave or Catalina.
Thank you for your recommendations.
after installing any of those macOSes on the external drive, did you go into System Preferences > Startup Disk and choose the external drive as your startup drive?
See above. Thank you.
The problem is the Preparation of EHD ( External HD ) as HFS Journaled / GUID. Wherein Catalina Requires or will convert the HFS Journaled Drive format to APFS / GUID and is required for Catalina
See above. Thank you.
Looking but do not see it.
Yes I did. And that is where the EHD with Catalina didn't show up, only the IHD with Sierra was listed.
Catalina on an EHD
