Next tides of users slowly notice that a number of unneeded files is installed on their systems. They enumerate systemd unit files, logrotate files, take their pitchforks and start their cruciates against Gentoo developers wasting their precious disk space.

Let me tell you a story. The story starts when Uncle Scarabeus wants to add bash-completion support into libreoffice ebuild. He considers this a minor addon, not worth the half a day necessary to rebuild libreoffice, so he doesn’t revbump it. He simply assumes the change will be propagated nicely when users upgrade to the next version.

Of course, some users will already come shouting here: that’s against the policy! Yes, indeed it is. But is it worth the hassle? Should all libreoffice users be forced to rebuild that huge package just to get a single tiny file installed? He could wait and add that along with the next version. Well, if he wouldn’t forget about it.

But that’s not really important part here. Because, to his surprise, many users have actually noticed the change. That’s because the use of bash-completion.eclass has caused the ebuild to have IUSE=bash-completion ; and many of the --newuse Portage option users have rebuilt the package. A few others, like me, just stopped using that option.

That’s when the discussion started. We — the few devs actually caring about discussing — decided that it is quite pointless to control installing tiny files through USEflags. Of course, the libreoffice is an elephant-case here but so-called regular packages aren’t much better here. Is there really a reason to rebuild even 10 C files when the only thing going to change is a single, tiny text file being installed or not?

Another solution is to split those files into separate ebuilds. But that’s usually inconvenient both for users and devs. Users have to notice that they need to emerge an additional package to get the particular file installed, and devs need to maintain that additional package. That starts to become really ridiculous with files like systemd units which are often generated during build-time and store installation paths.

So what to use? INSTALL_MASK , obviously. It’s an ancient Portage magic which allows you to control which files will be punted from installed files. You can use app-portage/install-mask to quickly set it for the files you don’t want. It’s as simple as: