You could do worse than to try and manually unmount the disk (without ejecting it) before the erase. This has worked for me before. You’ll use Terminal.
Make sure you use the MBR partition scheme with your FAT file system when creating it. Use the “Erase” function (as of El Cap) or Partition (for prior versions of OS X) but on the disk, and not the volume. In other words, select the disk by hardware description, not by volume label, in Disk Utility. First, to unmount, find your disk name in Terminal using “diskutil list” and then use “diskutil unmountdisk name” (where “name” is the whole disk). This unmounts every volume on that disk. You want a whole device name, like /dev/disk3, for example, and not a slice, like /dev/disk3s1. Then go to Disk Utility, select the whole disk in question (it should still be visible), choose Erase, set a volume label and set the scheme to Master Boot Record, and try and erase again. Expand the details view. Look at the results table. You should see both partition and mkfs steps. If it fails, let us know where exactly it failed. -- The following information is important for all members of the Mac Visionaries list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. Your Mac Visionaries list moderator is Mark Taylor and your owner is Cara Quinn - you can reach Cara at caraqu...@caraquinn.com The archives for this list can be searched at: http://www.mail-archive.com/macvisionaries@googlegroups.com/ --- You received this message because you are subscribed to the Google Groups "MacVisionaries" group. To unsubscribe from this group and stop receiving emails from it, send an email to macvisionaries+unsubscr...@googlegroups.com. To post to this group, send email to macvisionaries@googlegroups.com. Visit this group at https://groups.google.com/group/macvisionaries. For more options, visit https://groups.google.com/d/optout.
