Clean up installation

[Zill]

...Compared to a clean install (3.1 GB) there were 4.5 GB, so I am asking right now, where the 1.4GB come from?...

I have followed this thread, as an experiment, with interest and agree that there is possibly scope to improve the performance of apt-get.

Having said that, unused packages in a system generally do not cause any problems and, with HDD storage currently costing around 6p (10c) per GB, I do question if any such work would be cost-effective.

[Esokra]

It would still be nice, as the system would be more clean and transparent. I think if we have the power of a central package management system in unix like system, we should use the power. Suppose an app installs spyware libaries. In this case you want a reliable way to remove all the packages which were installed with a certain program. Furthermore, I do not want that ubuntu becomes such an untransperent system like windows, where every application can store as many registry keys as it wants.
Now I have another question, what about the write access to directories like /usr? Is a program blocked to, for example save logs in /usr instead of /home or /var? (If I understood this right, yes, as far as it does not run as root).

[Zill]

Esokra: FOSS cannot generally, due to it's open-sourcing, contain spyware or other malware.

In the unlikely event that a malicious "binary-blob" had been installed, I doubt if most users would be interested in trying to forensically remove affected packages. The quickest and easiest way to get a "clean" installation is simply to re-install the system.

...Now I have another question, what about the write access to directories like /usr? Is a program blocked to, for example save logs in /usr instead of /home or /var? (If I understood this right, yes, as far as it does not run as root).

I don't quite follow your question. /usr, like most system directories is owned by root with 755 permissions. This means that only root can write to the directory.

[Esokra]

Still, I would be interested in having a clean system, but your argument about cost-effectiveness is absolutely right.
Secondly, clean is not equivalent to new install, as I said, cleaning the system completely and get a system, that is like a new, makes no sense. This was only an experiment to prove, that apt-get does not catch all dependencies in terms of removing.
But my vision is, to keep the system clean (without reinstalling everything, which is not sensible, as it costs too much time and ressources for very complex systems, remember, you would have to reconfigure everything).
As said, this was an experiment, with the information i got, i hope to be able to write a script, which builds up on apt-get and is able to catch all dependencies when uninstalling a certain program (not turning a used system into a new). Sure, to make this possible, applications would have to be installed with my script. Maybe I will implement it in c++ (again, everything will be based on apt-get, but will be extended with information, apt-get is not able to get by design).
I will post details of a possible implementation, as soon as my rough idea is more perfect (and considers all possible issues). I will also provide more information, about the experiment.
I hope you stay interested and help by sharing ideas.

Thank you

[Zill]

...This was only an experiment to prove, that apt-get does not catch all dependencies in terms of removing...

I agree that this is an interesting experiment.

...But my vision is, to keep the system clean (without reinstalling everything, which is not sensible, as it costs too much time and ressources for very complex systems, remember, you would have to reconfigure everything)...

With most systems, a straightforward reinstall (i.e. of the same OS release) is fairly quick. Complex configurations can easily be restored from backups of, for example, the /etc directory.

...As said, this was an experiment, with the information i got, i hope to be able to write a script, which builds up on apt-get and is able to catch all dependencies when uninstalling a certain program (not turning a used system into a new)...

This is certainly one option. Alternatively, could you produce a patch for apt-get that would produce the desired results? This would probably be a "neater" solution.

[Esokra]

I have already read very much about this topic. As far as I understand there is nothing wrong about apt-get.
All the requirements to keep the system clean do already exist, but it requires manual work and knowledge how to keep the system clean and remove a program with all its dependencies (I am not talking about dependencies needed by other apps, as this would make absolutely no sense).
I will continue to research an implement a confortable and automatic way.

[Cheesemill]

If you use the aptitude command instead of apt-get to install and remove all of your programs then all unneeded dependencies are removed. This is one of the reasons it's the first thing I install on any system before adding any other packages.

In your case I don't think it would have made a difference because it only tracks dependencies of packages that were installed using aptitude.

[Esokra]

I have read very much about dpkg and deb packages. But this issue seems impossible to solve for me because of one issue: dpkg scripts. There seems to be no automatical way to undo the changes made by these scripts. They can create files and folders where they like and if the remove script does not undo these, the changes remain. This information can be found in

/var/lib/dpkg/info

I know a good package should not be any issue, still I ask myself, whether it is possible to undo really all changes made by the package manager, in case the package is of bad quality?

[LuisGMarine]

This might be a little off topic, but what about using Ubuntu Tweak? After installing Ubuntu 12.10 and running all the updates, I ran the Janitor feature in Ubuntu Tweak and it was able to delete over 100MB in unused packages and random files that could be deleted.

Just my two cents, but I"m going to follow this thread considering it is a very interesting topic.

[Zill]

...I know a good package should not be any issue, still I ask myself, whether it is possible to undo really all changes made by the package manager, in case the package is of bad quality?

As long as you stick to the official repos for a supported release you really should not get a package of "bad quality"!

In the unlikely event of a "rogue" package getting through, it should be a simple matter to manually remove the offending package(s) or to regress to an earlier version. A full history of package changes, including dependencies, is logged in /var/log/apt/history.log. Earlier versions are zipped with a numerical suffix eg. /var/log/apt/history.log1.gz etc.