Glibs uses /etc/nsswitch.conf to decide at runtime which libraries has to be loaded dynamically to implement DNS resolver, user lookup etc. One in principle can

Glibs uses /etc/nsswitch.conf to decide at runtime which libraries has to be loaded dynamically to implement DNS resolver, user lookup etc. One in principle can compile those libraries statically, but it is rather complicated for no gains, so almost nobody is doing that.