The defaults command for the command "make usb-image" generate a read-only image, but when the actual target system boots the image is found to be read-write
configure --enable-rootfs=glibc_small+debug --enable-kernel=standard --enable-board=qemux86-64 make fs make usb-image < /dev/null make start-target TOPTS="-disk export/usb.img" TARGET_QEMU_KERNEL="" # Login and run touch testing123 halt -p # Now boot the target again: make start-target TOPTS="-disk export/usb.img" TARGET_QEMU_KERNEL="" # You will see the file is there with "ls" and the image was mounted read-write