Why are many of my packages marked as manually installed

Question

I just realized that many of my packages are "manually" installed:

root@deb:~# apt-mark showhold
root@deb:~# apt-mark showmanual | wc -l
202
root@deb:~# apt-mark showauto | wc -l
371

I know eg from here that this happens if you upgrade only one specific package, but I did not do this for 202 packages.

Anybody has a guess how this might have happened?

Are there any downsides of having so many manual packages?

What are principal differences between manual and auto installed packages?

I can change them all to auto installed, but is this risky, could something go wrong when doing this??

Answer 1

The basic set of packages installed by default when the system is initially set up are marked as manually installed, as are any packages explicitly named for installation or upgrade with apt install or similar tools. This means that many packages you don’t think of as manually installed (because you don’t explicitly want them) will nevertheless be marked as manually installed.

You can run

apt-mark minimize-manual

as root to remove unnecessary markers.

The difference between automatically and manually installed packages is that the former will be considered for auto-removal when no other package depends on them.