[yocto] Distro vs. Image

[Leo Schwab]

Up to this point, all our builds for our prototypes have been "image"
builds, i.e. we built an image recipe starting with
packagegroup-core-boot, and it's accreted from there.  We write the
resulting .sdcard image file to an SD card and boot from that.

Now we would like to create an "installer" image, i.e. a bootable
image whose job is to install a release(-candidate) image to the HW.
Naturally, some config details in the resulting image will be
different.  The more I read, it feels like this wants to be a
"distro," rather than just another image recipe.  Recipes searching
for files will automagically generate subdirectory search paths based
on current distro name, which would allow us to substitute different
config files based on what's being built.  (Extra Credit for this
build would be to incorporate a copy of the release image into the
installer image.)

Trouble is, none of the docs I've read describe very clearly how to
make the leap from cobbling image recipes together to creating a
functionally equivalent distro recipe.  Could someone point out some
resources and examples on how this is meant to be conceptualized and
used?  Thanks in advance for all suggestions.

Schwab