I'm installing VirtualBox on one of my remote Linux servers and installed the software from their repository that deploys all the additional packages required by VirtualBox.
Still, when I first started the graphical interface, most of text appeared as funny characters that can't really be read:
This is a common problem when you're trying to run a graphical (X11) application on a server without graphics system like Xorg. As you probably guess, the problem is to do with fonts.
Specifically, it's a problem of your remote Linux server not having any fonts installed, because Xorg (graphics system) was never installed on it (servers usually have server-specific version of distro or at least a package selection that disables desktop related things).
Once we install standard fonts package like this:
greys@s5:~ $ sudo yum install xorg-x11-fonts-Type1 ... Installed: xorg-x11-fonts-Type1.noarch 0:7.5-9.el7 Dependency Installed: libXfont.x86_64 0:1.5.2-1.el7 libfontenc.x86_64 0:1.1.3-3.el7 ttmkfdir.x86_64 0:3.0.9-42.el7 xorg-x11-font-utils.x86_64 1:7.5-20.el7 ...
… restarting application will result in a normal window with quite readable fonts: