Adding docs for booting netboot.xyz on Digital Ocean

docs/usage_digitalocean.md

@@ -0,0 +1,48 @@
+### Digital Ocean
+
+[Digital Ocean](https://www.digitalocean.com) at one point had iPXE support loaded within their SeaBIOS but has since removed it.  In order to get around this, we'll have to rely on the Grub bootloader instead.
+
+iPXE generates linux bootable kernels so that you can boot iPXE directly from Grub.  It then treats the initrd as an embedded script which contains your networking and details to load up netboot.xyz.` 
+
+### Booting from Grub2
+
+#### Download an iPXE linux kernel
+
+Obtain an iPXE generic kernel [here](http://boot.netboot.xyz/ipxe/generic-ipxe.lkrn) or [compile your own](http://ipxe.org/download) and save it to /boot/generic-ipxe.lkrn.
+
+#### Create a netboot.xyz initrd file
+
+The netboot.xyz initrd file contains the script necessary to bring the instance on the network and reach out to netboot.xyz.
+
+Save as /boot/netboot.xyz-initrd (replace your networking information where appropriate):
+
+    #!ipxe
+    #/boot/netboot.xyz-initrd
+    imgfree
+    set net0/ip <instance public ip>
+    set net0/netmask <instance public netmask>
+    set net0/gateway <instance public gateway>
+    set dns <instance dns address>
+    ifopen net0
+    chain --autofree http://boot.netboot.xyz
+
+#### Add a Grub2 custom entry
+
+Add the following entry to /etc/grub.d/40_custom:
+
+    #/etc/grub.d/40_custom
+    menuentry 'netboot.xyz' {
+        set root='hd0,msdos1'
+        linux16 /boot/generic-ipxe.lkrn
+        initrd16 /boot/netboot.xyz-initrd
+    }
+
+#### Regenerate your grub config
+
+Run grub2-mkconfig right after editing the configuration to add the netboot.xyz entry to your grub menu:
+
+    grub2-mkconfig -o /boot/grub2/grub.cfg
+
+Load up a console and then reboot from the instance to catch the menu option.  You can also change the default boot to netboot.xyz or increase the timeout if you want to be able to catch it easier.
+
+

mkdocs.yml

@@ -7,3 +7,5 @@ pages:
     - 'HP iLO': 'boot_ilo.md'
     - 'Virtual Box': 'boot_vbox.md'
     - 'VMware': 'boot_vmware.md'
+- Provider Usage:
+    - 'Digital Ocean': 'usage_digitalocean.md'