title: Generate custom initramfs image with additional configuration files
body: <p>I would like to create an initramfs image for Debian Stretch which includes additional configuration files (say <code>/etc/a.conf</code>). </p>
  
  <p>What do I have to do prior to running <code>mkinitramfs -o initrd.img</code> in order for the image to include such files?</p>