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I wanted to start from scratch so I followed the guide that Apple has on their site. After rebooting and logging back in I saw that I have two different containers. Macintosh HD and Macintosh HD Data. Is there anyway to consolidate these into one? It says there's "Other Data" that's sitting at 22GB. No idea what that is and I'd love to clean up space on the Mac, that's why I wanted to restart from scratch.

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    Which guide did you follow, which version of macOS did you install? What is the output of diskutil list in Terminal (please edit the question and copy/paste the output into it)? – nohillside Feb 16 at 18:27
  • This is a good question. I got a new-to-me laptop and also have two disk drives like the above; this is in High Sierra. – FeliniusRex Feb 16 at 19:00
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    @feliniusrex if you see something like this in High Sierra it would be strange indeed. May be worth a new question focused on your setup. – nohillside Feb 16 at 19:08
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    The two-volume setup is normal and non-removable starting with macOS Catalina. The "Macintosh HD" volume contains system files, and is mounted read-only for security. The "Macintosh HD - Data" volume contains all user-modifiable files, installed apps, etc. See this question and the links in its answer for more details. – Gordon Davisson Feb 16 at 21:07
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    @GordonDavisson: You are correct, but Macintosh HD - Data should not appear in the image posted by the OP`. I have Catalina installed on 2013 iMac and Big Sur installed in a virtual machine. Nether show the Data volume. – David Anderson Feb 16 at 21:12
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For a Mac with a single internal drive, starting from scratch usually means erasing all partitions from the drive and creating a new GUID Partition Map with a hidden FAT32 formatted EFI partition and either a legacy Mac OS Extended (Journaled) formatted partition or a APFS container partition containing a single APFS formatted volume. The erase operation is usually performed by using the Disk Utility, but also can be performed by using the diskutil command.

Apparently, you either did not perform an any erase or erased a volume instead of the drive.

Once the drive is erased, a macOS can be installed. If required, any selected Mac OS Extended (Journaled) formatted partition will be automatically converted to APFS.

To show the drives in the Disk Utility window, select View>Show All Devices from the Disk Utility menu bar or press the key combination +2. Also from High Sierra, Mojave and Catalina, you can select Show All Devices from the pulldown menu shown below.

For Big Sur, the pulldown menu appears as shown below.

When erasing, you should get a popup asking for name, format and scheme. Below is an example from Big Sur. For scheme, you should always choose GUID Partition Map.

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  • Largely correct, but: 1. point out that all this (and the install) needs to be done in recovery mode (and how to get there), 2. You should not encrypt at this stage - encryption of boot drive should be done with FileVault after installation complete. – Gilby Feb 16 at 22:46
  • @Gilby: I removed the part about encryption. I not sure all forms a macOS recovery will allow erasing the entire drive. I will have test this before updating that part of my answer. I could also point out macOS can be installed to the internal drive by booting from a appropriately configured external drive. – David Anderson Feb 17 at 0:36

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