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OS X: Mount disks as read only or block automounting altogether #

Aaron Burghardt's open source Disk Arbitrator provides a simple GUI for changing OS X's automount behavior. Automounting can be disabled completely (especially handy for drive imaging / data recovery via ddrescue, etc) or mounts can be forced as read-only (for forensics, etc, though a hardware write-blocker is still recommended).
Disk Arbitrator
This little app replaces the following hacks I've been using to prevent automounting of USB / Firewire drives in OS X: UPDATE 1: Aaron kindly replied to my email, pointing out that the "stop" command (since removed) isn't necessary in the fourth method above and that pausing/resuming diskarbitrationd with SIGSTOP and SIGCONT offers another option (though it too disables diskutil):
   $ sudo launchctl list | grep diskarbitrationd
   188 -   com.apple.diskarbitrationd
   $ sudo kill -SIGSTOP 188 # pauses diskarbitrationd, disabling automount
   $ sudo kill -SIGCONT 188 # resumes diskarbitrationd, reenabling automount

UPDATE 2: More on disabling Disk Arbitration from Apple Examiner.

UPDATE 3: Mount USB drives as read-only in Windows

/mac | Aug 17, 2010


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