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Preventing automatic mounting of the partition in Mac OS X

How to stop system from mounting all partitions? You can find working solution inside.

Backup your data using Time Machine. Use USB or FireWire disk of greater capacity than you have on your Mac. I recommend using USB or FireWire instead of network because USB is faster.
You need to run the Disk Utility and format that disk with “Mac OS X Extended (Journaled)”. Watch carefully what you format. Formatting a wrong disk would destroy everything on that disk. Eject and physically disconnect the disk after backing up.©

Borrow a trick from Apple – set the partition type to something besides Apple_HFS. The Apple_Boot partition type is used by Lion Recovery, and should provide the exact behavior you want. This process is NOT for the faint-of-heart, and you should definitely have a backup. If any of this process is unclear, DO NOT DO IT. Note that all numbers and drive names will be different on your computer.

First, determine which “BSD disk” your target drive is. Very likely disk1, but not necessarily. For example, this is my current system:

bash-3.2$ diskutil list /dev/disk0 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *120.0 GB disk0 1: EFI 209.7 MB disk0s1 2: Apple_HFS Macintosh SSD 119.2 GB disk0s2 3: Apple_Boot Recovery HD 650.0 MB disk0s3 /dev/disk1 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *320.1 GB disk1 1: EFI 209.7 MB disk1s1 2: Apple_HFS Secondary HD 319.7 GB disk1s2 

We need to change the type of this partition. This involves noting partition parameters, deleting and creating a patition with gpt. Firsts, let find out parameters:

bash-3.2$ sudo gpt show disk1  start size index contents 0 1 PMBR  1  1 Pri GPT header  2 32 Pri GPT table  34 6 40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B  409640 246725744 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC 247135384 262144 247397528 1269528 3 GPT part - 48465300-0000-11AA-AA11-00306543ECAC  248667056 1402591 250069647 32 Sec GPT table  250069679 1 Sec GPT header 

Next, delete and add the partition. Note that we use values found on the previous step.

bash-3.2$ sudo gpt remove -b 247397528 -s 1269536 -t 48465300-0000-11AA-AA11-00306543ECAC  disk1 disk0s3 removed  bash-3.2$ sudo gpt add -b 247397528 -s 1269536 -t 426F6F74-0000-11AA-AA11-00306543ECAC  disk0 disk1s3 added 

Notice the different GUID. That is important because it tells OS X the type of the partition.

Check if everything is ok:

bash-3.2$ diskutil list disk1 

You should see what had previously been an Apple_HFS partition should be listed as Apple_Boot. Such partitions are bootable on an Intel Mac without being auto-mounted by a running system. Repeat this general process with each partition that you want to “hide” normally.

Source: Dmitry Dulepov’s blog

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Written by Stikine

March 7, 2012 at 04:22

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