Error 5 trying to use time machine with a remote drive.

Hi everyone, I'm trying to share a external USB HDD from Mac Mini with MacOS Catalina to use for Time Machine, my client Mac is a Macbook Pro 16" (intel) with Sonoma.

When I try to use to activate a Time Machine from the Macbook Pro with Sonoma with that disk appears this error: The operation couldn’t be completed. (com.apple.TimeMachine.SettingsExtension error 5.)

Searching a solution I found the problem is a security update in MacOS Catalina (maybe can works on Ventura too) that change permissions on "smbd" program.

A solution for this is give permissions to smbd to read/write all complete disk:

1. Open system Preferences
2. Security & Privacy
3. Privacy tab
4. Full Disk Access
5. Click on "+" to add an entry (if you can't click the "+" icon, make click on the padlock and authenticate with an administrator account or just type your password)
6. Press Command + Shift + g  (or Command + G , see the G is uppercase)
7. copy or type this: /usr/sbin to go to sbin folder, click o go
8. find and choose "smbd" file
9. See that recent added "smbd" is checked
10. Done! your share disk is Ok to use in Time Machine client.

I found the solution in this link thanks to VideoBeagle user: https://forums.macrumors.com/threads/cant-connect-to-mounted-usb-drives-over-network-after-catalina-upgrade.2357001/ 

You can apply this for the AFP (AppleFileServer) program too.

Remember that you can share APFS disk only with smbd, AFP ins't supported anymore for disks formatted with APFS.

I hope this helps.

Did you verify that the Time Machine (TM) destination drive, that you have attached to the iMac, that this Mac is configured to be "shared as a TM backup destination?"

Ref: Backup disks for Time Machine - Apple Support

Let's try something simple.

1. Remove this destination drive from TM on your laptop.
2. On the iMac, turn TM sharing off, then back on.
3. Re-add the destination drive to TM on your laptop.

I'm having exactly the same issues as the OP and have followed to the letter the guidelines you offered. I get exactly the same error message, the only slight difference is my iMac is running Catalina 10.5.7 (my MacBook is Sonoma) Is that the problem causer?

Thank you

Great! I'm glad you got it worked out.