Michael Stone wrote:
> Debian is a general purpose OS that can form the foundation for a lot
> of variants. But, that flexibility has a cost, and the cost is size &
> complexity. /var/lib/apt and /var/lib/dpkg alone are the size of a
> minimal linux distribution, without even accounting for actual
> executables. You can shrink the minimal set by making some components
> replaceable, but for a general purpose OS that implies the 60k
> update-alternatives program plus /etc/alternatives plus
> /var/lib/dpkg/alternatives--all to support reconfiguration that won't
> ever happen in a container image.
Omitting whole directories like /var/lib/dpkg and /var/lib/apt (for
finalized containers that will never get more packages installed atop
them), or /usr/share/{doc,info,man,locale} (for most containers) is
straightforward and easy, and any container optimizing for size starts
there.
And the extra symlinks in `/etc/alternatives` don't take much size; I
agree you don't need update-alternatives, but then, you also don't
strictly need the entire dpkg and apt packages, if you're already
omitting their files under /var/lib.
Omitting other packages is harder, and more error-prone. And that's the
area where `Essential` makes it much harder. If there were explicit
dependencies, it'd be a matter of carefully pruning the DAG, rather than
a matter of carefully manually checking what has an unststated
dependency on what.
