I'm trying to downgrade from Catalina to Mojave, and I need to backup all of my files without backing up operating system files. Time Machine takes a backup of everything on the disk meaning that macOS Catalina files are also included. I need a way in which I can install macOS Mojave on my Mac and keep my personal data. What's the best way to backup a hard drive without Time Machine?

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    You never said which files you are interested in keeping. – Allan Apr 20 '20 at 12:05
  • What have you tried? – fsb Apr 20 '20 at 12:09
  • @Allan he said that he wants all files except OS files. – Todd Apr 20 '20 at 13:07
  • @Todd That's pretty vague - what are "OS files?" Application preferences? Which ones? System-wide on the OS side of things or in his personal Library? – Allan Apr 20 '20 at 13:08
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    @Todd I just recently wrote an answer with a preface on assuming things... It's never a good idea to assume the OP meant this or that...it's good as a hunch, but always best to get clarification as to what they actually want. – Allan Apr 20 '20 at 13:18

You can try copying all of the home folders located in /Users. After copying all the folders there to the external hard drive, you should check if all the data you want is there. After that, you can boot from macOS Recovery and erase the startup disk. After doing that, use a bootable macOS Mojave installer to reinstall macOS on the Startup Disk.

To do that, first read this on creating bootable macOS Installers: https://support.apple.com/en-us/HT201372.

To boot from that drive, you need to shutdown or restart your computer with the macOS Installer plugged in. Then, hold "Option" while the Mac is starting to boot from the installer. Once you are in, click reinstall macOS and choose your startup disk.

After macOS Mojave is installed, boot from the internal startup disk. Finish setup and create a new user. Once you are in, copy all your home directories from the SSD to the /Users directory. Then go to System Preferences and create new users and set the home directories to the home folders that were copied and remove the user that was created at the setup of macOS Mojave. Reboot the machine and you technically have your data back.

NOTE: Some compatibility issues may occur with personal files when switching from macOS Catalina to macOS Mojave.

  • "you should check if all the data you want is there." How is this done? For example, I remotely connect to a server through SSH that I don't need to put a password in for, where would I "check" to see if that info is still there? Also, I have a lot of bookmarks saved in Firefox or Chrome. Where would I go to check that those files are backed up? Time machine takes care a ton of this for you, provided you use it for restoration. Now the user wants to do this manually - how does one go about doing this? – Allan Apr 20 '20 at 13:25
  • @Allan Ummm... you just click on the external drive in Finder and see if the data is there? This doesn't need any SSH. If you want your bookmarks then you also have to copy the /Applications data. – Todd Apr 20 '20 at 13:27
  • I didn't ask that. I asked you to explain your step "you should check if all the data you want is there." How does the user know what to check if they don't know what was backed up? (And re: my SSH question - you totally botched the answer). And Bookmarks aren't installed in /Applications – Allan Apr 20 '20 at 13:29
  • Of course the user knows what was backed up because they are doing it. You need to read the answer and comment completley. I said "you just click on the external drive in Finder and see if the data is there" in the previous comment. Again, read before posting comments that waste people's time. – Todd Apr 20 '20 at 13:32
  • I did, thus my comment. You spent more time on booting, something the OP didn't ask and one sentence on backing up which up to now, you can't explain beyond repeating yourself. This doesn't waste peoples, time - it serves as a warning to avoid this answer. – Allan Apr 20 '20 at 13:34

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