That file is indeed the one that generates the official perl image. It
starts "FROM debian:buster-slim"

Now we could assume the official LMS image could be built by a process
that would start "FROM perl:5.028-slim-buster" (or so)
Meaning, since official images from Docker Hub are multi-arch, the LMS
build process would magically pull the buster+perl:5.02 image built for
the right arch ...
... and from there something has to happen to make LMS appear within
that buster+perl image, resulting in an "official" LMS image.

When installing the LMS image you would see various parallel "pulls"
happen, (at least) one for buster, one for perl, one for LMS. Each of
these are stored in a different directory/layer, the filesystem of an
image/container is the fusion of these layers. (visit /var/lib/docker,
you'll see what I mean)
This is efficient(*) because if next you'd pull, say, redis:latest, and
that image is built "FROM debian:buster-slim" too, then you wouldn't
pull and store the buster part again, since the same layer is already
present somewhere in /var/lib/docker/

In other words, a user pulling the LMS image built "FROM
perl:5.028-slim-buster" would certainly have to download the LMS
layer(s), possibly have to download the perl layer(s), probably not have
to download the buster layer(s) since the image is often taken as
starting point.


*)There is also a tragic consequence to this: every line in a Dockerfile
-except a few like USER, ENV...- generates a new layer. That's why you
see Dockerfiles where commands make ample use of continuation lines, to
try keeping the number of generated layers in check)



2 SB 3 • 1 PCP 6 • Libratone Loop, Zipp, Zipp Mini • iPeng (iPhone +
iPad) • LMS 7.9 (linux) with plugins: CD Player, WaveInput, Triode's BBC
iPlayer by bpa • IRBlaster by Gwendesign (Felix) • Smart Mix, Music Walk
With Me, What Was That Tune? by Michael Herger • PowerSave by Jason
Holtzapple • Song Info, Song Lyrics by Erland Isaksson • AirPlay Bridge
by philippe_44 • WeatherTime by Martin Rehfeld • Auto Dim Display,
SaverSwitcher, ContextMenu by Peter Watkins.
------------------------------------------------------------------------
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