What is com.apple.MobileSoftwareUpdate.UpdateBrainService?

I have it running and using a lot of CPU resources. (about 300% CPU core in top)

I also found out it would mount a partition at /System/Volumes/Update/mnt1 when it's running. I am not 100% sure if this mount point is related to this process. It's just my observation.

I am running MacOS Big Sur 11.2.3 (20D91).

My auto update is always turned off.

I found two online links talking about it, link1 and link2. But they don't explain what it is and why it's running.

Thank you very much.

Update 1:

I figured out even if I have Automatically keep my Mac up to date turned off. There is an Advanced... button in Software Update preference.

In the Advanced... setup popup window, it has the following options enabled: Check for updates, Download new updates when available.

I think this might cause com.apple.MobileSoftwareUpdate.UpdateBrainService process running and downloaded Big Sur updates. I am not very sure. Just a guess.

Update 2:

I have clicked Restart in Software Update preference. Now, my system updated to 11.4.

I have turned off Check for updates in Advanced... window.

Hopefully, this issue and process will never run again.

1 Answer 1


Found a great detailed explainer on the whole process at The Eclectic Light Company:

... the update takes three phases: download, preparation, and installation. The second of those, run by the Update Brain Service com.apple.MobileSoftwareUpdate.UpdateBrainService, assembles all the components required, verifies them, decompresses data and readies it for the final phase.


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