Backing up laptop to external disk connected to iMac using Time Machine

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Level 2

224 points

Backing up laptop to external disk connected to iMac using Time Machine

I can't figure this out, any help appreciated.

I am trying to setup an external disk attached to an iMac as a backup disk to be used by Time Machine on my laptop.

I have added the disk to File Sharing via System Preferences and clicked the disk > Advanced Options and selected Share as Time Machine backup destination.

I've added the administrator as having Read & Write access.

I can select the disk from Sys Pref > Time Machine from my laptop and when I enter the admin credentials, they're accepted.

However when the 120 seconds countdown and the backup tries to start, I get these messages. I have tried just about everything. Has anyone had any experience with this? Very frustrating, thanks!

iMac with Retina 5K display, macOS 10.15

Posted on Jul 13, 2020 5:32 PM

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Answer 1

Best reply

Tom Torrillo Author

Level 2

224 points

Jul 15, 2020 1:02 PM in response to Tom Torrillo

Ok so here's the deal, after getting frustrated with trying to change the permissions for a shared external disk, the changes weren't saving and were reverted upon going back into Sys Prefs > Sharing, I changed the permissions via Finder which then showed up correctly under Sys Prefs > Sharing and now my laptop is correctly connecting and backing up via Time Machine to the external disk connected to my iMac.

Sounds like a bug when trying to share an entire external disk via Sharing vs. a folder on a disk.

TLDR; To backup over your network to an external disk attached to a Mac, change the permissions via Finder, not the Sys Pref > Sharing pane.

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Answer 2

Tom Torrillo Author

Level 2

224 points

Jul 15, 2020 12:41 PM in response to BDAqua

The-Torrillos-iMac.local

I have added the external disk as a shared folder location and set it to SMB and Share as a Time Machine destination.

The System Administrator has Read & Write permissions.

There's another weird thing that might be related. I am sharing the entire external drive, not a folder within as shared folder. If I try to alter the permissions, say change Everyone to Read & Write, the change takes but if I close Sys Pref and go back in, it will not have stayed changed and reverts back to Read Only. Same goes for any permissions I add like say another user, Sys Prefs takes the addition but if I close out and go back in, the user I just added is not there.

Is there something weird about adding an entire drive as shared that I don't know about?

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Answer 3

BDAqua

Level 10

240,911 points

Jul 13, 2020 8:11 PM in response to Tom Torrillo

Sounds like it's trying to backup to the internal drive, in Sys Prefs>Time Machine, remove the Disk shown under Select Disk, & see what it says for Available Disks, not a Network drive.

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