what is it about an eMMC flasher image that causes it to flash?

hoping i'm reading this correctly, an eMMC flasher image is used the
same way you would simply boot off an sD card normally -- insert uSD
card, hold down BOOT button, and plug in power, forcing BBB to boot
off of uSD card.

  so what is it exactly that invokes the flash utility inside the
flasher image? i'm familiar with the contents of the top-level
"build/" directory, i can see how mkcard.sh and emmc.sh work, and so
on. but what kicks off emmc.sh in the *first* place?

  assuming that the kernel invokes /sbin/init in the flasher image,
that's a symlink to /lib/systemd/systemd but i'm not a systemd expert
so i'm not sure what happens after that.

  am i asking the right question?

rday

oh, wait, think i found it -- that would be
/lib/systemd/system/emmc.service, correct? carry on ...

rday

hoping i’m reading this correctly, an eMMC flasher image is used the
same way you would simply boot off an sD card normally – insert uSD
card, hold down BOOT button, and plug in power, forcing BBB to boot
off of uSD card.

so what is it exactly that invokes the flash utility inside the
flasher image? i’m familiar with the contents of the top-level
“build/” directory, i can see how mkcard.sh and emmc.sh work, and so
on. but what kicks off emmc.sh in the first place?

assuming that the kernel invokes /sbin/init in the flasher image,
that’s a symlink to /lib/systemd/systemd but i’m not a systemd expert
so i’m not sure what happens after that.

oh, wait, think i found it – that would be
/lib/systemd/system/emmc.service, correct? carry on …

Affirmative.