I think that you need to add a package.
Ex) Add the following to build/conf/local.conf IMAGE_INSTALL_append = " e2fsprogs"
For details, please refer to Yocto manual.
Ygohda (talk)
Thank you very much for having you teach it. I try it. I report the result some other time.
Kazu (talk)
Thanks to you, I was able to format eMMC. And I was able to write in Linux image at eMMC.