Mac OS X 10.2: MS-DOS Disk Does Not Appear in Finder

A local MS-DOS (FAT32) volume, whether a whole disk or a partition, will not appear in the Finder ("mount") if it is larger than 128 GB.
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  • The MS-DOS volume does not appear on the desktop or in a Finder window.
  • In the log file /var/log/system.log, there is a line containing "mountmsdosfs(): disk too big, sorry".

Note: "Local" volumes are those that are directly connected to your computer, including hard drives that connect via ATA, SCSI, USB, and FireWire. This issue does not affect remote volumes, such as "shares" on a Microsoft Windows server.


If your computer has a hard drive that is larger than 128 GB and that must be used locally in MS-DOS format, partition it so that no individual partition is larger than 128 GB. You could also share the disk from another computer and connect to it from your Macintosh.

The remainder of this document provides more information on partitioning and sharing.

How to partition

Connect the drive to a computer that is using a Microsoft Windows or Linux operating system. Use an appropriate disk formatting utility to partition it so that each volume is smaller than 128 GB.

Warning: With most disk utilities, partitioning a disk requires erasing the whole disk. Be sure to back up any files you wish to keep before partitioning.

    1. The Disk Utility application included with Mac OS X allows you to format an entire hard disk as MS-DOS, but it will not allow you to choose MS-DOS when partitioning. Therefore, Disk Utility may not be used as a solution in this scenario.

    2. Disk Utility allows you to initialize a hard disk larger than 128 GB as MS-DOS, but it will not appear in the Finder after being initialized.

    3. If you are transferring a hard drive that was installed in another computer to a Macintosh and plan to use it only in the Macintosh, you may use Disk Utility to reformat it as something other than MS-DOS (Mac OS Extended, for example). Though the disk will not appear in the Finder prior to initialization, it will still be available to Disk Utility.

How to share the disk

Connect the hard drive to a computer using a Windows or Linux operating system. On that computer, share the disk using either SMB (Windows or Samba service) or FTP. Refer to Windows or Linux documentation for information on how to set up sharing.

Note: Though some non-Apple systems offer an Apple sharing service (AFP), you should not use it in this case.

To connect to the disk from a Mac OS X computer:
  • If you share using SMB, connect your Mac OS X computer using the Connect to Server command in the Finder, as explained in technical document 106471, "Mac OS X 10.1 or Later: How to Connect to Windows File Sharing (SMB)".
  • If you share the disk via FTP, you may connect with a Web browser (by starting the address with "ftp://" instead of "http://"), or by using a dedicated FTP application program.

Important: Information about products not manufactured by Apple is provided for information purposes only, and does not constitute Apple's recommendation or endorsement. Please contact the vendor for additional information.

Document 17159, "Locating Vendor Information" can help you search for a particular vendor's address and phone number.
Published Date: Oct 7, 2016