title: Reading GRUB2 debug logs
body: <p>I want to see GRUB2 debug logs generated by grub_dprintf(), for example, at mmap.c:</p>
  
  <pre><code>  grub_dprintf ("mmap", "EFI memory region 0x%llx-0x%llx: %d\n",
          (unsigned long long) desc-&gt;physical_start,
          (unsigned long long) desc-&gt;physical_start
          + desc-&gt;num_pages * 4096, desc-&gt;type);
  </code></pre>
  
  <p>After some research, I found out the way to enable this log is by setting debug env variable at grub menu (I changed it on grub.cfg, probably am not supposed to do this)</p>
  
  <pre><code>set debug=all
  </code></pre>
  
  <p>How can I check the logs?  The grub logs scrolled so fast during boot that it is hard to check.  Perhaps there is a way to check the logs after kernel boots?</p>
  
  <p>I am using CENTOS 7.</p>