Note

Changing the opencore.iso means that upgrading will need extra steps to re-implement your changes.

The opencore.iso file is a hybrid between a CD and a disk image. It can be mounted as a writeable USB drive by changing a setting in the guest VMX file.

1. Make sure that the VM is shutdown and closed in VMware. You may want to ensure you do not have snapshots if this is a permanent change to the VM.
2. Open the VMX file, usually macos.vmx, in a text editor and find this line:

usb_xhci:0.readonly = "TRUE"

4. Change the line as shown:

usb_xhci:0.readonly = "FALSE"

5. Save the VMX file and then boot the VM
6. (Optional) After making the changes you may want to set it back to a read-only CD. Just reverse the changes to the VMX file.

These changes can also be automated using the vmxtool in the tools folder, under the subfolder that matches your operating system. Note the you cannot have spaces around the "=" on the command line but they are added in the file.

Enable RW mode:

vmxtool set <vmx file> usb_xhci:0.readonly="FALSE"

Enable RO mode:

vmxtool set <vmx file> usb_xhci:0.readonly="TRUE"

For reference the VMDK descriptor file is a simple text file:

# Disk DescriptorFile
version=1
encoding="UTF-8"
CID=fffffffe
parentCID=ffffffff
isNativeSnapshot="no"
createType="monolithicFlat"

# Extent description
RW 81920 FLAT "opencore.iso" 0

# The Disk Data Base 
#DDB

ddb.adapterType = "lsilogic"
#ddb.geometry.cylinders is not used by Mac OS.
#ddb.geometry.heads is not used by Mac OS.
#ddb.geometry.sectors is not used by Mac OS.
#ddb.longContentID will be generated on the first write to the file.
#ddb.uuid is not used by Mac OS.
ddb.virtualHWVersion = "6"