Prevent Encrypted Partition From Mounting at Boot

Absolutely do not hack your system as discussed in the second thread.

Please post the contents of the fstab file you created.

It seems that the fstab method doesn't work with CoreStorage volumes.

There is no way I know of to prevent automounting of CoreStorage volumes selectively. You may be able to prevent all CS volumes from automounting by deleting or commenting out the "LaunchEvents" key in this file:

/System/Library/LaunchDaemons/com.apple.corestorage.corestoraged.plist

I haven't tested this hack, I don't endorse it, and I have nothing else to say about it. Please don't ask me for help if it doesn't work or has unexpected effects.

I would really love to know solution for this problem. I have 2 encrypted partitions which I really want to prevent to get automounted automatically.

It is irritating when I log into the system and I get 2 dialogs asking for passwords even though I do not want these partitions mounted at all.

I've been struggling with this exact problem after encrypting two external volumes on a USB drive last week. I've been using the /etc/fstab method to prevent them from automounting every time I plug in the USB and this was working perfectly until I encrypted the volumes.

I thought it might be to do with the volume UUID used in the fstab file for the encrypted volume. If you use:

$ diskutil coreStorage list

you'll see different UUIDs listed for your volumes than what you get when you use:

$ diskutil info /dev/DISKID

I get something like (abbreviated and edited) when listing the coreStorage disks:

+-- Logical Volume Group UUID_A

| +-< Physical Volume UUID_B

| +-> Logical Volume Family UUID_C

| +-> Logical Volume UUID_D

However, I used UUID_A thru D in the /etc/fstab file and didn't have any success at all.

Haven't been able to find a solution yet, but still looking.

I have even tried to use LABEL and /dev/disk0s3 in /etc/fstab instead of UUID but with no success either 😟

Linc Davis wrote:

It seems that the fstab method doesn't work with CoreStorage volumes.

Yes, that's correct. Core Storage doesn't look at fstab at all.

If the only Core Storage volumes you have are encrypted containers, you can achieve the desired outcome by disabling boot time invocation of the Core Storage daemon. Please note that Apple's Fusion Drive technology relies on Core Storage, so if you have a system with Fusion Drive, this workaround may break your computer.

Linc Davis wrote:

There is no way I know of to prevent automounting of CoreStorage volumes selectively. You may be able to prevent all CS volumes from automounting by deleting or commenting out the "LaunchEvents" key in this file:

That's the idea, but good heavens, don't comment things out in launch plists! Do it right, use launchctl.

The Core Storage daemon normally runs at boot, and manages logical volumes assigned to Core Storage—specifically, in the OP's case, encrypted containers. If you have no other mission-critical Core Storage volumes, you may use the launchctl command to disable the Core Storage daemon, using the unload -w argument, as per the launchctl man page:

unload [-w] [-S sessiontype] [-D domain] paths ...

Unload the specified configuration files or directories of con-

figuration files. This will also stop the job if it is running.

-w Overrides the Disabled key and sets it to true. In pre-

vious versions, this option would modify the configura-

tion file. Now the state of the Disabled key is stored

elsewhere on-disk.

So, in Terminal, the command to prevent Core Storage from running at boot time would be as follows:

$ sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.corestorage.corestoraged.plist

Please note again that Apple's Fusion Drive technology relies on Core Storage, so if you have a system with Fusion Drive, this workaround may break your computer.

After disabling the Core Storage daemon, you may still mount encrypted volumes using Disk Utility, or the command line (hdiutil attach /dev/diskX where /dev/diskX is the encrypted container).

Hope this helps.

Thanks for such a comprehensive comment. This greatly explain how CoreStorage work.

In my case, I have my boot partition encrypted. This prevents me to turn the CoreStorage off as I would not be able to boot.

I.e. if one has a boot partition encrypted, there is no way to prevent another encrypted drive to get mounted on boot automactically. Or at least no one knows if this is possible.