Solved How to change system font?

How and where can I change the default system font? For now it appears to be DejaVu 10, which is quite horrible on my laptop.

By default system font I mean the font that is used in menus or labels. For example when I open Firefox for the first time or any KDE application for the first time (Konsole, Okular, etc) all menus and labels are drawn using DejaVu 10. Chromium appears to be using its own font. The font used for menus and label doesn't appear to be changeable from the application itself so I guess there must be some setting in the system itself. Does it depend on the window manager? I am using Lumina at this moment.
No idea if this is related:
gtk-font-name = "DejaVu Sans 8"

Juha, trying to sweep my ~ but it's always full of graffiti
I think it depends on the Windows/Desktop manager. Cinnamon for example sets the default font via System Settings -> Fonts. As far as I know Chrome/Chromium has its own font settings (including a default font).
I dont' have that file in none of my environments and in fact I don't have dejavu in any of the config files in my home directory. It must be some system-wide setting.
Lumina also sets the default font which it uses in its menus and dialogs. But first time I started Lumina it had this ugly DejaVu 11 as default. I changed that but it doesn't change the default font for other applications, just for Lumina.
Maybe that's not the right part of the Handbook but, somewhere in there it shows how to do this. I just don't recall how to myself this morning.
It's about how to install fonts and how to configure particular font features. I couldn't find anything about configuring which font is the default one. It could be that it's GTK-related since the default DejaVu isn't used in all applications, just some of them. Is there any place to configure default font for GTK? In my system I have ~/.config/gtk-2.0/gtkfilechooser.ini but not ~/.gtkrc-2.0
It is, it is. I expected something bad would happen, but no, you really _can_ have the proverbial cat-sized letters :)


Oh, thanks. I tried and indeed it worked with Firefox and some other applications. But Konsole still stubbornly uses DejaVu 10. But at least it's some progress. It seems to be GTK-related rather than XOrg.
Thanks, that's what I just found out too. Just trying to search how to change the default font for QT....
amiramix, If you're using applications designed to integrate into a major desktop environment--KDE, GNOME, Cinnamon, Xfce, LXQt--the aesthetic settings are controlled by that DE's centralized settings app, which in turn stores settings in a variety of media (some settings are stored in plain text, some in binary databases). This means that if you're mixing and matching GNOME and KDE applications, you have two choices: either learn the internals of the DE those applications belong to and then manually change the settings; or install the core components of each desktop environment, including their settings applications.

Desktop environments are designed to provide a well-integrated interface and universal experience. They aren't, strictly speaking, modular components that you can mix and match as you like without hassle. You might be able to get a working solution by installing x11-themes/lxappearance for GTK2 applications and misc/qt4-qtconfig for Qt4 applications. I don't believe the former works with GTK3 applications (those used by GNOME and Cinnamon), and the latter won't work with KDE applications (which are built with QT5). But to be blunt, if most of the applications you're using are KDE applications (as per your first post), then all the core KDE stuff is already installed on your system. You might as well just take that last step and install Plasma.
I would rather install the core settings applications for those environments but without installing whole environments if possible. But it's not easy to find out which applications those would be or which config files they would be changing if I wanted to update them manually. Even if I install Plasma, can I run the KDE config application without running KDE? I will have a look at lxappearance and I am installing qt4-qtconfig to see if it helps.
For the record, qt4-qtconfig worked perfectly for me. The font for all KDE applications that I have installed could be changed with it. So this, plus the ~/.gtkrc-2.0 setting sorted it out for me.