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Create partition on APFS internal disk to download Catalina

How do I create a partition on my APFS internal disk drive to install Catalina?

I'm running Mojave on a 2013 MacBook Pro with an APFS formatted internal drive. Because I have several 32 bit apps that I use I don't want to upgrade the entire Mac to Catalina. My thought was to create a 50 GB partition on my internal drive, download Catalina to the partition, and use that as a Catalina boot drive. Thus, I would have a dual-boot Mac where I could choose to boot up either in Mojave or Catalina.

However, unlike for a Mac OS Extended (Journaled) drive, Disk Utility does not present a partition option for my APFS drive. I can create a "volume", which I did. I tried to down load Catalina to the volume but not sure it worked. When I try booting up holding the Option key, I don't get the volume as a bootable option. Only the internal drive shows.

So, is my above plan the way to be doing this, or is there another way? Also, is my partition procedure incorrect?

Thanks in advance.

-- Rich

Posted on Apr 14, 2022 4:41 PM

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HWTech

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Posted on Apr 16, 2022 6:50 PM

The Catalina installer does not download as a .dmg file. It downloads as a standard app into the Applications folder titled something like "Install macOS Catalina". You can find links to various macOS installers as well as optional instructions for creating a bootable macOS USB installer:

How to create a bootable installer for macOS - Apple Support

You need to properly prepare the destination drive by using Disk Utility to erase the destination drive as GUID partition and APFS (top option). Then install macOS and select the newly erased drive as the destination for the installation of macOS which will make the selected drive into a full macOS boot drive.

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Apr 28, 2022 1:54 AM in response to HWTech

Hi HWTech

There is a risk in everything but that’s why I always have one or two bootable backups.

He who dares wins – but a planned careful dare.

I have had an external hard drive (with multiple boot partitions) that has had partitions deleted and retrieved several times without trouble. I did once have an internal SSD that when I “retrieved” the partition it wouldn’t give back as free space but the original Mojave OS etc of 190GB was using 491GB of the 500GB drive. Still worked ok though. Got out of that easily by taking a clone, booting into the clone, reformatting the SSD and putting the clone back, getting 310GB free space. No worries.

I do not agree it is much safer and would be slower on an external drive plus the inflexibility if carting around external drive with a laptop. Sure if having Mojave and Catalina on two partitions doesn’t work could think of this alternative. It is also cheaper not to have to buy Parallels etc and although I have not used I imagine that might not be plain sailing.

I would still highly recommend trying the two systems on the one SSD, repeating, ad nauseum, have One or Two bootable backups. Incidentally I have two internal SSDs both of which have working Mojave and High Sierra OS and I can boot from any one.

Rich839

Please keep us informed on how you get on with partitioning the SSD and whether you can get Mojave and Catalina booting from the same SSD. Have fun and learn.

Rich839 Author

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May 6, 2022 10:55 AM in response to Rich839

As a final status update, I partitioned my internal APFS Mojave drive and booted Catalina on the partition. So far it works fine. I can boot up in either one of the operating systems.

The boot drive that I had previously created with the USB3 thumb drive allowed a Catalina boot, but Catalina functioned so slowly as to be unworkable.

Thanks to all of you who posted suggestions on this thread.

-- Rich

May 1, 2022 1:55 AM in response to Need_help_give_help

I have put all secondary backups and test volumes in the same container (Big Sur + Mojave on an internal drive also worked OK like that but now only Monterey on the internal disk):