I am following instructions for creating a Bootable drive (generously provided in this answer by a gentleman named David Anderson). I am using a 16GB SD card to try to create a Bootable drive from my MacBook running Catalina.

The instructions could be simplified by doing a Restore using the Disk Utility to the external drive (SD card or flash drive), with BaseSystem.dmg being the restore source.

The problem is that when I try this, I get the following error (also see screenshot)

Could not validate sizes – Operation not permitted. The operation couldn’t be completed. (OSStatus error 1.)

What does this mean? Is there a better way to fix this than the one given in David Anderson's answer. Or, can the asr command be made to work reliably, so the Disk Utility would not have to be used?


  • Are you attempting to create a bootable installer of Catalina or simply a USB flash with Catalina installed on it?
    – Allan
    Apr 29, 2020 at 21:45
  • A bootable installer Apr 30, 2020 at 3:50
  • Ok..so you also said "...from my MacBook running Catalina." Why not just download the installer and use createinstallmedia per Apple's instructions? This seems like a rather roundabout way to accomplish this.
    – Allan
    Apr 30, 2020 at 12:27
  • @Allan: I edited the question. My answer, that the OP was referring to, involved an El Capitan installer. May 1, 2020 at 20:21

4 Answers 4


I think the "Operation is not permitted" may be caused by Disk Utility lacking the necessary admin privileges.

sudo /usr/sbin/asr restore --source BaseSystem.dmg --target /Volumes/MyVolume --erase

Should do the trick (terms and conditions apply)

  • This is what worked for me, thanks!
    – Roger
    Jun 22, 2020 at 17:13
  • 1
    This worked! I also had to open Disk Utility and prepare the source image via Images > Scan for restore... Jul 4, 2020 at 20:19
  • I had to put quotes around the source and target parameters for this to work, e.g. --source "BaseSystem.dmg"
    – Andreas
    Jan 18, 2021 at 8:58
  • 1
    This worked for me in attempting to re-install Mac OS X Lion (previously bought in App Store) on an old Macbook. Benign error messages: Checksum failed. Expected 7425D663 but got 84E748B9 Could not restore - Invalid argument Jul 5, 2021 at 18:52
  • 1
    This almost worked for me. It did not succeed doing it straight from the DMG though. I had to mount the DMG and use the mounted directory as the source. Jul 19, 2021 at 16:56

You can do it easily using ASR command

  • You have to scan your downloaded image via following command

    sudo /usr/sbin/asr imagescan --source ~/Downloads/macOSUpdCombo10.15.7.dmg 
  • After scan you have to run following coammand to restore the image into the USB.

    sudo /usr/sbin/asr restore --source <IMAGE_PATH> --target /Volumes/<VOLUME_NAME> --erase

If there is any issue, please share in here.

  • 2
    I found that before imagescan would run I had to convert the source image to read-only using the image Convert command in Disk Utility.
    – nmgeek
    Nov 15, 2020 at 4:21

Ok, first of all, to be clear, you are doing this from macOS Recovery or while you are booted up on the bootable USB installer right? Also, a 16GB SD card is not enough to hold macOS Catalina. If you are looking to make an SD card that has a ready installation of macOS Catalina, then you can download the Install macOS Catalina app and then use that to install on the SD card (again, the amount of storage isn't enough). https://support.apple.com/guide/mac-help/reinstall-macos-mchlp1599/mac.

If you are experiencing issues with creating a bootable installer, then I think your best option would be to download the Install macOS Catalina app from the App Store and then use the creatinstallmedia command to create the installer. See the link for more https://support.apple.com/en-us/HT201372.

  • I edited the question. My answer, that the OP was referring to, involved an El Capitan installer. AFAIK, there has been no mention by the OP or me of installing Catalina on a SD card. May 1, 2020 at 20:30
  • @DavidAnderson The question was unclear so I provided instructions for both.
    – Todd
    May 1, 2020 at 20:32

if you have access to Terminal you can:

  1. list your disks

    diskutil list to get your SD_CARD_NAME

  2. unmount your SD card

    diskutil unmountDisk force /dev/SD_CARD_NAME

  3. erase it with the desired file system (AFS or JHFS+)

    diskutil eraseDisk JHFS+ Emptied /dev/SD_CARD_NAME

Then go ahead with your restore

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