If you have the problem described for example here, you can’t boot with newer ElRepo-kernels because the kernel driver für your Realtek ethernet card ist not loaded into the initrd environment, you can add them into /etc/dracut.conf
add_drivers+=”r8169 realtek “
and rebuild the initramfs with something like
dracut -f -v /boot/initramfs-5.8.5-1.el7.elrepo.x86_64.img 5.8.5-1.el7.elrepo.x86_64
grub2-mkconfig -o /boot/grub2/grub.cfg
