How do you disable auto-mounting of ALL new/unknown drives on OS X? This article describes how to disable automount on a specific drive:


But then you have to know the drive UUID. And to find out the UUID you would have to mount the drive, and the second you do that OS X auto-mounts the drive as read+write and starts writing lots of hidden files to the drive (.Spotlight-V100, .Trashes, .fseventsd, .metadata_never_index) before you can say "cake". This is particularly bad if the connected drive is a faulty drive you are going to to rescue work on, then you obviously don't want the Operating System to write to the drive at all.

So what do you do to get complete control of the mounting process?

2 Answers 2


Aaron Burghardt's Disk Arbitrator does almost what you want. While it's running, it can be set to either reject new mounts, or force new mounts to be read-only (or it can be disabled, so new mounts happen normally). However, it applies its policy to all volumes attached while the program is running (whether or not they've been seen before), and it does not apply to volumes attached (and hence mounted) at system startup (i.e. before you have a chance to run the program). But it's open source, so if it't not close enough to what you want you might be able to modify it...

(BTW: credit goes to @chrisk for bringing Disk Arbitrator to my attention in this earlier answer to a similar question.)


From MacOSXHints.com:

Prevent disk auto-mount while logged in (Category: Storage Devices)

Jul 27, '10 07:30:00AM • Contributed by: tobyvoss

While there are numerous well-documented ways to prevent a hard disk or USB drive from mounting at boot-time, I found only one way (working in 10.6) to prevent newly-connected disks from auto-mounting while logged in.

It is possible to turn off the responsible process:

sudo launchctl unload /System/Library/LaunchDaemons/com.apple.diskarbitrationd.plist

This has negative repercussions on general ejecting and mounting. Turning diskarbitrationd back on with load instead of unload doesn't solve all problems, either.

So I looked far and wide for a simple GUI tool performing this function; all I found were expensive forensics-toolkits for law enforcement which offer this function on the side.

Then I stumbled upon this gem: github.com/aburgh/Disk-Arbitrator/. Works for systems 10.5 and up, source available, binaries available (in 'Downloads'), all problems solved!

[crarko adds: I tested this, and it works as described. Nice utility, with good documentation.]

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