macOS howto format usb drive to dos compatible, max 4GB

 diskutil eraseDisk FAT32 MY_DISK1 /dev/disk2

linux (eg. ubuntu) format USB and check health status

 usb drive doesn't have health data. 

First, find the drive device using df  or  lsblk

Eg. unmount the device sdc1

$ umount /dev/sdc1

Format usb drive to FAT32 on linux

    $ sudo mkfs.vfat -F 32 /dev/sdc1

Check disk for bad blocks by writing different byte patterns

WARNING!  Write mode is destructive. 

    $ sudo badblocks -w -s -o  myusb.log /dev/sdc

        # write-mode,  show progress, output to file 

# non-destructive 

    $ sudo badblocks -nvs > usberr.log /dev/sdc

# or through   fsck  or  mkfs

    # option:   -fcky    or      -fccky    # one 'c' read-only,  'cc'  read-write non-destructive

HOWTO convert ubuntu 18.04 LTS ISO to bootable USB installation disk on Mac OSX

minimum 2GB size of SD card

0) find name of SD card in file system

diskutil list

1) download from ubuntu.com the 18.04 LTS image

cd ~/Downloads/

ls ubuntu-18.04-desktop-amd64.iso

2) convert ISO to dd-table binary image

hdiutil convert -format UDRW -o ubuntu1804.img ubuntu-18.04-desktop-amd64.iso

3) unmount SD card, eg. disk3

diskutil unmountDisk /dev/disk3

4) write to SD card

sudo dd if=./target.img.dmg of=/dev/rdisk3 bs=1m