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Question: Multiple "OS X Base System" mounted / system freeze on disk operations


I'm running macOS High Sierra 10.13.3 (17D47) on MacBook Pro (Retina, 15-inch, Mid 2014)

I recently started to observe complete occasional unexpected system freeze on disk operations. I.e. at some moment UI continues works, but when app needs any load/save, even if I switch to terminal and run `ls`, app freezes. After several disk operation attempts (i.e. several apps requires disk access and frozen) seems that some disk queue overfills and system freezes with flower cursor. Then I can switch between windows, some of them update their content (except for windows waiting for disk) but I can not do anything in any windows that require disk. Only hard reboot helps. I think it started when I upgraded to High Sierra and it happens one-twice per month completely random (as I observe it, but I believe there's reason for that).

For the reference, I never reboot my mac except for situations like this or system updates.

While investigating problem I opened Disk Utility and observed huge number of mounted "OS X Base System"

Initially it is one or two, but while system runs I can observe up to a hundred.

Any idea is multiple "OS X Base System" is an issue?

Any idea if it can be connected with system freeze?


Screenshot for the reference:

User uploaded file

MacBook Pro with Retina display, macOS High Sierra (10.13.3)

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Mar 16, 2018 5:52 AM in response to I'm Matvey In response to I'm Matvey

You have an SSD, so storage access speed should not be slow. I am assuming this is the original Apple SSD storage.

I suspect you have a memory problem. As is very little free memory, so when you switch apps, or want to do things that need memory for their operation, macOS needs to push things out before it can free up enough to do what you ask.

I also find all those "OS X Base System" images to be interesting. What happens if you unmount them (click on the triangle next to each).

I would look at Applications -> Utilities -> Activity Monitor

Change the "View" to all processes.

And see how much free memory there is when you start to have these issues. And/Or from a Terminal session

/usr/bin/top -ocpu -R -F -s 5

It would also be interesting to see the EtreCheck output

<> or <>

Use the EtreCheck -> Edit -> Copy Report (See the image below)

User uploaded file

User uploaded file

And then Paste the report as a "Reply" to this thread.

If, AND ONLY IF, you get the error:

"The message contains invalid characters"

then try posting to, and give us a PasteBin URL link.



EtreCheck is a tool that helps Apple Support Community volunteers debug problems without any access to the troubled computers. Debugging problems can be a difficult task even when the machine is in front of you. Attempting it via a discussion forum is extremely difficult. EtreCheck is a great help that regards.

Mar 16, 2018 5:52 AM

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Question: Multiple "OS X Base System" mounted / system freeze on disk operations