How To: Boot a Mac into FreeDOS for Bootable, SpinRite or ReadSpeed (Part 3 of 3 - Booting the Mac)

[Scott]

This How To is in Three Parts:

1. Part 1 - Intro
2. Part 2 - Media Creation - How to make a bootable USB on your Mac for Bootable, ReadSpeed, or SpinRite
3. Part 3 - Booting your Mac - How to get your Mac to boot from external media instead of the internal hard drive - this post

Booting your Mac - How to get your Mac to boot from external media instead of the internal hard drive​

Here's how to how to boot a Mac from a USB flash drive into FreeDOS to run DOS-based utilities like Bootable, ReadSpeed or SpinRite.

First, of course, make sure you have a flash drive with FreeDOS on it as outlined in Step 2 above. Then try the three methods below, in order from simplest to most complex.

1. Option key method -- try this first, as it's the simplest:
   • Insert your flash drive with the Mac off. On startup, hold down the Option key. You'll boot to the Mac's graphical Boot Manager, which should show all volumes from which the Mac can boot. If you see a USB drive icon with the Volume name "Windows", then select that Volume and press Enter. If your FreeDOS drive was prepared correctly and is compatible (more on that below), your Mac should boot into FreeDOS. If you don’t see the Volume on the Boot Manager, you should try disabling SIP.
2. Disable SIP, then try Option Key method
   • Are you running MacOS version 10.11 (El Capitan) or newer? Then the option key method above probably won't work without first disabling SIP (System Integrity Protection), which is sort of Apple's equivalent of Secure Boot on PCs.
     1. Check if SIP is enabled. Open the terminal, from the command line type:
        • csrutil status
     2. If status is disabled AND you already tried the Option Key method, then proceed with Step 3B. Else disable SIP and try the Option key method again
     3. Disable SIP -- unmodified Mac (not using Open Core Legacy Patcher
        1. Turn off your Mac (Apple > Shut Down).
        2. Hold down Command-R and press the Power button to boot into Recovery Mode
        3. Wait for MacOS to boot into the MacOS Utilities window
        4. Choose Utilities > Terminal, and at the terminal prompt enter
           • csrutil disable
        5. You should get confirmation that SIP is disabled
        6. Restart your Mac (or Shut Down and then Power On)
        7. Now hold down the Option key and select the drive, as noted in 1, above
     4. Disable SIP -- using Open Core Legacy Patcher
        1. Open OCLP
        2. Select the settings button at the bottom of the window
        3. Select the "Security" menu
        4. Under "System Integrity Protection," select all the checkmarks.
        5. Exit the settings
        6. Build and install OCLP
        7. Reboot
        8. Now hold down the Option key and select the drive, as noted in 1, above

3. Software selection method -- more complex​

This method requires you to use some command line programs to tell MacOS that on the next reboot, it should look for a BIOS-based OS on the flash drive rather than MacOS on the hard drive. Steps for this method follow.​

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A. Disable SIP (System Integrity Protection)​

Are you running MacOS version 10.10 (Yosemite) or older? Then you can skip this step and go on to Step B. Otherwise you must disable SIP. Just disable SIP as noted in 2A, above.​

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B. Use the bless command to tell the Mac to restart in BIOS/CSM/Legacy mode​

1. With the Mac up and running (and SIP disabled as noted), insert the FreeDOS USB; it will be recognized and show up on the Desktop​

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2. Open a terminal window. Run the "diskutil list" command, to see the device assigned to the USB drive. On my machine it was /dev/disk2​

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3. From the terminal, type the following after the prompt$:​

sudo bless --device /dev/disk2 --setBoot --nextonly --legacy --verbose​

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a. You'll probably be prompted for your root password which you obviously must enter​

b. In the above command, obviously replace disk2 with whatever the device is that's assigned on your machine. Also, very important to have the --nextonly flag, else maybe this is a permanent change!!​

c. IMPORTANT:​

i. if the output of the bless command says "Legacy mode supported" AND you DON'T see something like, "could not set boot device property: 0xe00002bc" (or some other similar code) then you can proceed​

ii. if the output of the bless command says "Legacy mode supported" AND you DO see something like, "could not set boot device property: 0xe00002bc" (or some other similar code) then you probably did not disable SIP correctly​

iii. if the output of the bless command says "Legacy mode not supported on this system" then your Mac does not support BIOS/ CSM/ Legacy mode, and you will not be able to boot FreeDOS​

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4. Do a standard restart from the Apple menu. Your system should now boot from the USB into FreeDOS on the next start. Congratulations!! After power down, your system should boot normally from the hard drive into MacOS​

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5. The boot flash drive should be readable and writable, and if you boot the system with other USB drives plugged in, those drives may be visible to SpinRite as well (listed as BIOS-accessible drives).​

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I'm running Open Core Legacy Patcher, will this work for me?​

OCLP is a tremendous program which allows older Macs to run newer versions of MacOS than they were designed for. In order to do this, OCLP writes additional UEFI drivers to the MacOS disk and adds additional information to the Mac's PRAM pre-boot environment; it also partially disables SIP. Because SIP is disabled, a Mac running OCLP can usually boot FreeDOS just by using the Option key method noted above.

If that doesn't work, you could try disabling all aspects of SIP:

1. Open OCLP
2. Select the settings button at the bottom of the window
3. Select the "Security" menu
4. Under "System Integrity Protection," select all the checkmarks.
5. Exit the settings
6. Build and install OCLP
7. Reboot

If you do that, I'd suggest going back to the defaults on OCLP after your work with the GRC utilities is done. Simply rebuild OCLP with the defaults for your machine and reboot.

Problems!​

1. System reboots but instead of starting FreeDOS, you get the message:

"No bootable device -- insert boot disk and press any key"​

This is because the system is failing in two ways:​

A. It's not reading the MBR on the flash drive correctly and so it then shifts into EFI mode, but...​

B. It doesn't see a valid EFI boot disk layout and so it fails.​

What to do about it? Try creating a different FreeDOS disk on a different brand of flash drive. I used InitDisk on 11 different flash drives of varying brands, and only 5 of them could be seen by the Mac as valid boot drives.​

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2. System reboots but you just get a grey screen.

This is also, I think, a symptom of the Mac's picky behavior with USB drives. I saw this when using the Option key method to start my Mac, but:​

A. Other USB drives would boot into FreeDOS​

B. The problematic drive would work when using the software selection ("bless") method.​

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Only suggestion is to try another drive.​

3. System boots to FreeDOS but seems flaky, hangs, etc. I'm not sure, but I think that this may be a sign that the system is overheating. Macs may control their fans primarily through software, and FreeDOS will certainly not know how to control a system fan in the background! Any insight from users would be appreciated here.

Comments?​

Comments welcome!

 

[wls]

SYSTEM INFO: iMac (27-inch, Late 2012) 3.4GHz Intel Core i7, 32GB Memory, 4TB Disk
USB Full Keyboard w/ Numeric Keypad, USB Logitech Trackball; USB Flash Drive was 256GB, Formatted FAT16
​

The instructions for making bootable media on a Mac worked great. However, @Steve, I've run into two minor problems I wanted to pass your way:

1. After booting to the Windows USB stick, if I touch nothing else, I get a big blue Congratulations message -- but then the keyboard is dead; I can't press any key.

WORKAROUND: The moment you select the Windows USB stick to boot, immediately start pressing Return over and over, don't stop, filling the keyboard buffer. This is important -- keep pressing past the "FreeDOS" in good old 80x25 text, a flash of blue, and likely into several DOS prompts. You're then good to go.

REASON FOR REACHING OUT: Didn't know if there was something in your boot sequence that left the keyboard in a weird state that you might want to look into.


2. I have downloaded my purchased copy of SPINRITE.EXE v6.1 (270,768 bytes, though I suspect the SHA Hash would be useless, since each copy is personalized and unique).

When I go to run it, it says: SpinRite's internal health self-check failed. Something may have altered SpinRite from its original download. Please obtain a new fresh copy of your personal edition of SpinRite. (I did, it didn't work.)

THE PROBLEM: If you're like me, you likely have earlier versions. I put my SPINRITEs in directories named: SPINRITE.50, SPINRITE.60, and SPINRITE.61. Meaning this is what I did above:

C:\> cd SPINRITE.61
C:\SPINRITE.61> spinrite

THE WORKAROUND: Just copy the SPINRITE.EXE to the root directory of the USB stick and run it from there. It's that simple. SpinRite will start right up!

REASON FOR REACHING OUT: It seems that the health check is location dependent, and that seems kind of silly.

 

[Scott]

1. After booting to the Windows USB stick, if I touch nothing else, I get a big blue Congratulations message -- but then the keyboard is dead; I can't press any key.

…..


2. THE PROBLEM: : It seems that the health check is location dependent, and that seems kind of silly.

Hi @wls , in part 2 of this thread, in the Notes section for Bootable, I wrote that on my Mac, Bootable didn’t respond to key presses. I did report this to Steve who couldn’t see a reason in the code why that would happen, and closed the issue with a “Will not fix” status.

I noted on that page that even if the Mac hung, as long as you can see the Bootable success message, SpinRite should boot and run.

As for the health check, I have no insight there, that’s an issue for Steve.

 

[peopleware]

SOLUTION on my system: *keep* pressing the Enter key after selecting the USB boot drive especially during the "Congratulations" flash screen: after 4-5 seconds, Spinrite starts loading and the Spinrite main screen shows off

This on a Macbook Pro Retina 15 inch mid-2012, holding the Option key to get all the boot disks available

NOTE: the external disk I want to scan *must* be plugged into the USB port, as the boot USB drive, *before* powering the system

 

[AlanD]

NOTE: the external disk I want to scan *must* be plugged into the USB port, as the boot USB drive, *before* powering the system

This is typical for most machines, any USB devices must be plugged in when the PC starts for them to be seen by the BIOS. BIOS does not support hot plugging, it is the OS that does.

 

[Scott]

NOTE: the external disk I want to scan *must* be plugged into the USB port, as the boot USB drive, *before* powering the system

In Part 1 of this tutorial I wrote:

If I can get this to work, what drives will SpinRite see?​

Internal drives​

SpinRite should be able to see the internal drives on your Mac, either by using its native AHCI and IDE drivers, or as BIOS-attached drives.

USB-attached drives​

In my testing, if I had a USB drive connected to the Mac when booting the FreeDOS disk with SpinRite, then SpinRite would detect the USB drive as BIOS-attached and be able to operate on it as well as the internal drives.

• This capability may vary among different Mac models.
• For at least some Macs, BIOS-attached drives (including USB-attached drives) will not be recognized if they are over 2.2 TB

 

[Jamie Cox]

Comments?​

Comments welcome!

I'm here to report success booting SpinRite 6.1 on a Late 2013 MacBook Pro (Retina 13-inch), using these instructions. (Thanks! Lots of detail here.) I did experience the unresponsive keyboard problem when testing with Bootable, but SpinRite itself runs fine. I was successfully able to boot using this flash drive. (Amazon link)

I was also able to get SpinRite 6.1 working on a 2018 Intel MacMini under VirtualBox, but that didn't seem very reliable. I think MacOS 15 was occasionally changing the disk permissions and/or remounting the drive while SpinRite was running, which causes SpinRite to be unable to access any sectors after that.

FYI, I wrote the SpinRite-On-Mac-under-VirtualBox instructions here, in case they are helpful to anyone. They were originally written for SpinRite 6, and may still be applicable for Macs that can't boot SpinRite directly.

 

[Scott]

I'm here to report success booting SpinRite 6.1 on a Late 2013 MacBook Pro (Retina 13-inch), using these instructions. (Thanks! Lots of detail here.) I did experience the unresponsive keyboard problem when testing with Bootable, but SpinRite itself runs fine. I was successfully able to boot using this flash drive. (Amazon link)

I was also able to get SpinRite 6.1 working on a 2018 Intel MacMini under VirtualBox, but that didn't seem very reliable. I think MacOS 15 was occasionally changing the disk permissions and/or remounting the drive while SpinRite was running, which causes SpinRite to be unable to access any sectors after that.

FYI, I wrote the SpinRite-On-Mac-under-VirtualBox instructions here, in case they are helpful to anyone. They were originally written for SpinRite 6, and may still be applicable for Macs that can't boot SpinRite directly.

I’m glad this worked for you, Jamie. I took a look at your VirtualBox instructions, maybe you want to compare them to what I wrote up here.

My assumption was that a user would want to run SR against the boot disk, hence the instructions for creating an external boot disk.