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Question

Time Machine Configuration Profile adds system disk to Exclude from Backups list

  • December 19, 2024
  • 3 replies
  • 194 views
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I am trying to create a basic Time Machine Configuration Profile to backup users to a SMB share.

 

After initially realising my mistake that the SMB share would need to authenticate based on the Computers AD credentials rather then the users credentials. (as the time machine process does not run as the console user) I am now able to see the SMB share listed as a valid time machine backup disk. 

 

The problem that I have is the client computers system disk has been added to the "Exclude from Backups list". Obviously I have not included this in the Configuration Profile and changing the various "Tick boxes" doesn't seem to help.

 

Is there a reason the computers system disk would be added to the "Exclude from Backups list" 

 

As part of the MDM profile?

As the result of the setting in another none time machine profile?

Due to a setting on the the system disk?

 

(Problem exists for both Arm and Intel's running Mac OS 15.2)

Any help appreciated 

    3 replies

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    • mnsasd
    • New Contributor
    • December 31, 2024

    The system disk being added to the "Exclude from Backups" list in your Time Machine Configuration Profile may be due to default macOS settings or an MDM policy conflict. macOS typically excludes system disks to prevent backing up system files that are already part of the OS.

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    • Jobless-Loser
    • Author
    • New Contributor
    • January 2, 2025

    The system disk being added to the "Exclude from Backups" list in your Time Machine Configuration Profile may be due to default macOS settings or an MDM policy conflict. macOS typically excludes system disks to prevent backing up system files that are already part of the OS.


    Hi mnsasd

     

    By the computers system disk I mean the computers built in ssd.

    adamscybot
    • adamscybot
    • New Contributor
    • September 6, 2026

    Hi. I just came across this, and have resolved it.

    On macOS 26.6.2 (and probably multiple previous versions and ones to follow...), Apple’s schema doesn’t match ManagedClient’s behaviour: BackupSkipSys defaults to true, not the documented false, and BackupAllVolumes=true includes all volumes, despite its description saying “only the startup volume”.

    Explicitly setting both resolved the issue for me, including after reboot:

    <key>BackupAllVolumes</key>
    <true/>
    <key>BackupSkipSys</key>
    <false/>

    BasePaths alone wasn’t enough. Explicitly exclude any external disks or mount paths you don’t want backed up.

    There's still something else funky going on because the omitted settings should still allow user data to be backed up, and not implicitly exclude the startup disk like it does. In my case I noticed the previous broken saved configuration included the APFS System volume’s UUID but excluded the Data volume’s UUID, despite both appearing as “Macintosh HD”. That suggests a separate volume-selection bug, or bad state that may/may not be caused by omission of the above settings and resulting weird defaults. None the less, the above sorted it for me.

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