OS X: Disable Automount for a Specific Partition

In order to do this, you have to fire up a bit of terminal. If you are not familiar with the underlines of UNIX, you should document yourself more before proceeding. So, I have a partition which I do not want to be automatically mounted on reboot because it is used by one virtualbox machine. 1. List the partitions with diskutil command: mini:~ osx$ diskutil list

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *128.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS mini                    127.2 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
/dev/disk1 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *3.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS 3T                      2.4 TB     disk1s2
   3:                  Apple_HFS vbox                    610.0 GB   disk1s3

2. Once you find the target partition, do again diskutil on it but with info option:

mini:~ osx$ diskutil info disk1s2
   Device Identifier:        disk1s2
   Device Node:              /dev/disk1s2
   Whole:                    No
   Part of Whole:            disk1
   Device / Media Name:      3T

   Volume Name:              3T

   Mounted:                  No

   File System Personality:  Journaled HFS+
   Type (Bundle):            hfs
   Name (User Visible):      Mac OS Extended (Journaled)
   Journal:                  Unknown (not mounted)
   Owners:                   Disabled

   Partition Type:           Apple_HFS
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 USB
   SMART Status:             Not Supported
   Volume UUID:              00000000-1B11-3GSG-B5E1-E00440844CD5
   Disk / Partition UUID:    00000000-CA38-4222-9778-2B1852C44C61

   Total Size:               2.4 TB (2390080942080 Bytes) (exactly 4668126840 512-Byte-Units)
   Volume Free Space:        0 B (0 Bytes) (exactly 0 512-Byte-Units)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (not mounted)

   Device Location:          External
   Removable Media:          No

3. Get the Volume UUID and add it to /etc/fstab but do not edit it directly. Use instead the command sudo vifs and add the following line to it: UUID=00000000-1B11-3GSG-B5E1-E00440844CD5 none hfs rw,noauto

mini:~ osx$ sudo vifs
mini:~ osx$ cat /etc/fstab
#
# Warning - this file should only be modified with vifs(8)
#
# Failure to do so is unsupported and may be destructive.
#
UUID=00000000-1B11-3GSG-B5E1-E00440844CD5 none hfs rw,noauto

DONE!