Just Code it!

Update: Written for OSX El Capitan. Works for macOS Sierra as well.

While VirtualBox is a great product easy to use to create Virtual Machines and configure in few minutes, trying to create a Virtual Machine with a OSX system could be very tricky.

With this guide I will explain a procedure you can follow if you want to install a Mac OS X system on VirtualBox, running on Max OS X as well.

I wanted to describe this because the information available are often confused, missing and too many times they require the download of extra software or installer (generally to avoid the very common issue where the UEFI Interactive Shell is displayed or the text “Fatal: no bootable medium found! System Halted”, that you can see if you selected EFI support for your Virtual Machine).

If you find this useful or interesting please share and comment for more to come!

Time to start!

Create ISO from installer

The very first thing to do is to download the OS X Installer.

I wrote a dedicated post for this and you can find it here:

Create Mac OS X Installer USB Disk

Time to do some magic!

As it stand the installer will not work on the Virtual Machine (and you will experience the error I mentioned at the start of the article).

What we’ll need to do is manipulate the installer disk in order to make it ready for our Virtual Machine to understand.

I will put the whole list of commands at the end of this article, but I will explain every line to make it clear what’s going on.

We’ll make heavy use of the “hdiutil” tool.

It is a command used to manipulate disk images and you can find detailed about this command here:



1. Attach the installer image

First thing we need to do is attaching the image of the installer (that we downloaded) as a device. Effectively simulating a device (the installation disk in this case) attached to our mac.

We achieve this using the “hdiutil” command: “attach“.

The disk we want to attach is contained in the app you downloaded from the App Store: “/Applications/Install OS X El Capitan.app

Inside its content: “/Contents/SharedSupport/InstallESD.dmg

(So essentially in: “/Applications/Install OS X El Capitan.app/Contents/SharedSupport/InstallESD.dmg“)

We’ll then proceed to attach this disk image and at the same time:

  • We’ll tell the system to hide the content of this disk from Finder with: “-nobrowse
  • We’ll no verify the image (with the checksums): “-noverify
  • and we’ll instruct it to mount it in a location where we will then intend to access its content. Let’s choose: “/Volumes/esd

That’s the full command:

2. Create new image

We want now to create a new image.

For this we’ll use the “hdiutil” command: “create”

  • We give the image an output file: “-o Installer.cdr
  • I’ll set the size to 7.5GB (you can increase it if you’ll need to): “-size 7.5g
  • Then we specify the layout of the image. We’ll use “SPUD“, that from the documentation: “SPUD causes a DDM and an Apple Partition Scheme partition map with a single entry to be written.”
  • For the filesystem (of the image) we’ll use the standard HFS+J: “-fs HFS+J

3. Attach the new disk image

We now attach the newly created disk image (still empty) to another volume. The command is conceptually identical to what we did before with “InstallESD.dmg”, but this time we attach the disk we just created “OSXInstaller.cdr.dmg”:

4. Copy the System Installer to the new disk image

The real installer is inside the disk image “BaseSystem.dmg” contained in “InstallESD.dmg” (that we attached to the volume “/Volumes/esd/“).

What we need to do is copy the content of this disk image (so the content of “BaseSystem.dmg”) into the root of our new installer disk (that we attached to “/Volumes/iso/“).

For this we use now the command “asr” that copies disk images into volumes and we just tell it to restore the image from “/Volumes/esd/BaseSystem.dmg” into “/Volumes/iso“.

The other options are to avoid verification and to skip the prompting of confirmation to continue (essentially to avoid to answer “yes” to the erase disk confirmation).

Note: the “-erase” option is now mandatory (or “asr” will refuse to run with the error: “File copy is not supported anymore.  Use the –erase flag.”).

This is the full command:

At the end of this passage the finder window pointing to our new “restored” disk (“Volumes/OS X Base System/“) should automatically popup:

and you can see that it is now mounted and available from the main finder as well:


5. Remove broken link

If you look inside “Volumes/OS X Base System/System/Installation/” you will see that there is a file “Packages” that is actually a link.

If you check where it’s pointing at (with “ls -l /Volumes/OS\ X\ Base\ System/System/Installation/Packages“), you will see that it points to:

/Volumes/OS X Base System/System/Installation/Packages -> /System/Installation/PackagesLink

That doesn’t exist.

In order to fix this we need to remove this link and put the real file in there.

We can remove it simply with:

6. Put back what the link was pointing to

Now it’s just a question to replace the link we just removed with the a real folder physically containing the files.

This is the folder “Packages” in the disk “InstallESD.dmg” (that we mounted in “/Volumes/esd/“).

Let’s copy it, preserving the property of the files (mode,ownership,timestamps) with the parameter “-p” and copying the directories recursively “-r“:

At the end of this the “Pakages” folder should be back in place (but for real this time, not anymore as a link) in the disk we are manually creating (the folder will be therefore in “/Volumes/OS\ X\ Base\ System/System/Installation/Packages“).

7. Copy the remaining missing files

If you look again in the original InstallESD disk, you can see other files in the root:

Ignore the two AppleDiagnostic files (we don’t care about these).

We need to copy the two BaseSystem files in the root of our disk:

8. Detach the volumes

We can now detach the source disk (“/Applications/Install OS X El Capitan.app/Contents/SharedSupport/InstallESD.dmg“) that we mounted in “/Volumes/esd“:

And the one we created (from “/Volumes/esd/BaseSystem.dmg“) and found in “Volumes/OS X Base System/“:

9. Create ISO disk

To use the installer in VirtualBox we need to convert our disk to iso, otherwise you would receive an “VERR_NOT_SUPPORTED” error.

To convert our dmg disk in iso we’ll use again the “hdiutil” tool with the command “convert“:

The format we’ll use is: “UDTO – DVD/CD-R master for export”:

The generated file will contain the extra extension “cdr” that we need to remove if we want to see the disk from VirtualBox in order to select it later on.

We can get rid of it simply renaming the file with “mv“:

you can get rid of OSXInstaller.cdr.dmg at any point now (thanks to Brian for noticing this missing detail in a comment).

10. Done – Summary of the commands

The image is ready to use in VirtualBox. It’s name is now: “OSXInstaller.iso

This is the summary of the commands we run to create it for an easy reference:

Create the Virtual Machine

Open now VirtualBox (you can download it there: “https://www.virtualbox.org/“). I’m using version 5.0.20.

1. Creation

Proceed creating a new Virtual Machine. You can do this by clicking the blue icon (“new”) at the top:

Give a name. If you name it something like “OSX” VirtualBox will automatically select the type of Virtual Machine you want to create (“Mac OSX”):

Click “Continue” and select then the memory size in the next screen. I pick 4096MB:

Create a virtual hard disk:

Select the default VDI (VirtualBox Disk Image) disk type:

Go ahead and pick (if you want) Dynamically allocated:

Select then the file location (the name really) and size (I will create a 40GB HD):

At this point the creation procedure will complete and you should be able to locate your newly created Virtual Machine:

2. Configuration

Select it and click on the “Settings” button:

Select the “Display” section (subsection “Screen”) and fix the amount of Video Memory if it is something like 1MB or 8MB. Move it to the max 128MB:

Enter then the “Storage” section and select the “Empty” disk. Click the CD icon on the right and pick the “Choose Virtual Optical Disk File…” from the menu that will pop-up:

Locate and select the iso we created in the previous chapter (“OSXInstaller.iso“):

At this point press “OK” and we are ready!

Install OSX on the VM

We can now start the real OSX installation procedure!

1. Start the VM

Time to run our Virtual Machine for the first time! Click on the green “Start” arrow:

It should now start and you should see the console printing out a lot of data… wait patiently:

… and more…

Finally start the installation procedure selecting your language:

Click “Continue: on the next screen:

2. Create an HDD partition

To install the system we need to create an Hard Disk first. As you can see in the following image in fact the only visible drive is the CD with the installer:

This video will show how to create the disk and start the installation process that I will describe step by step immediately after:

To create it run the tool “Disk Utility” that you can find in the top menu under “Utilities”:

Select the Hard Disk on the left side (without any partition at the moment) and click “Erase”:

In the new window that will pop-up set a name (I named it “HDD”) and click the “Erase” button:

Wait for the procedure to complete and click “Done”:

You can the close Disk Utility:

3. Install OSX!

And you’ll have your new HDD ready to select and click “Continue” to finally start the installation procedure:

Time to wait…

4. Restart the VM

At the end of the installation the system will shut down.

At this point we can remove the installation disk from our virtual drive.

Go in Settings, Storage and then select the “OSXInstaller.iso” drive. Click on the disk icon at the right of “Optical Drive” and this time select “Remove Disk from Virtual Drive”:

The drive should now be empty again:

You can now run again the Virtual Machine and this time the second part of the OSX installation procedure should kick in:

Go ahead and complete the installation.

This video shows this procedure:

At the end you should finally be able to boot into your brand new freshly installed OSX Virtual Machine! :)


That’s all!

comment and share if this helped you or if you have any questions! :)