Create hidden partition?

Question

I am wanting to create a hidden partition, similar to the way Apple creates the recovery partition. Is this possible? That is, I could boot to the partition by holding down the option key, but it doesn't show up elsewhere. Searching has led me to some suggestions about modifying the /etc/fstab file to keep it from mounting, which is a step in the right direction (and could work if it's the best I can do) but the recovery partion goes a step farther, as it doesn't even show up in disk utility. Is there a way I can acomplish the same thing? Thanks.

Answer 1

Here is solution for this issue (Source: Apple Stack Exchenge)
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
What follows is a copy-paste-edit job from Dmitry Dulepov:
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.