apt - How do installs work? - Ask Ubuntu

i'm trying comprehensive understanding of common terms mean on end of things. "installing" program mean gets out directory, /bin or /opt, , has name added path in .profile file?

i under impression installing program meant there tons of files , modifications existing files scattered around os in various places. ever true?

if so, how 1 un-install that? keep os clean , organized, if can remove binary /bin, wouldn't know how clean install if leave tons of changes around os.

how work?

baseline

"installing" program broad term. actual definition

place or fix (equipment or machinery) in position ready use.

so basically, having in right position , setup able function , used properly. definition of term i'll using throughout answer.

process

apt (advanced packaging tool)

the actual "under-the-hood" process of apt-get explained muru in this post. covers what command , accesses. i'm linking answer because don't want duplicate same answer on different question, want reference it.

basic installation concept

theoretically, moving executable file bin folder , having bash environment point folder path, moving additional files directory (usually /var/) , referenced executable should fine "install" something. but, things downloaded , moved package varies between different packages mention later in answer. so, process isn't useful unless you're installing either own package know put files (even then, should package .deb file autonomy) or very basic package.

extra files

apt (advanced packaging tool)

this varies heavily each package installed. deals dependencies these things aren't explicitly telling ubuntu install, needs in order install package specified. if want remove these files then, in theory, have manually go through each dependency installed , remove them. but, there 2 ways deal these files without doing that. apt-get comes 2 useful commands,

• apt-get remove --purge [package]
• apt-get autoremove

the first command tells ubuntu remove configuration/extra files along core files of specific package. however, not remove dependencies installed package. that, have use our second command.

the second command tells ubuntu remove orphaned packages. orphaned package package installed dependency, no longer needed other packages. doing both of these commands remove files downloaded/installed original installation.

there may other minor things specific package installed need manually reverted such additional configuration files or default application associations, should easy reverse.

basic removal concept

as stated in basic installation concept section above, have move required files correct paths referenced bash , system environment. rid system of these files, reverse process going whatever directory placed in , remove them there. doesn't apply packages installed, basic concept.