Add TFTP to Services chapter

docs/services.rst

@@ -1052,6 +1052,48 @@ After commit the resulting configuration will look like:
        }
    }
 
+TFTP
+----
+
+Trivial File Transfer Protocol (TFTP_) is a simple lockstep File Transfer
+Protocol which allows a client to get a file from or put a file onto a remote
+host. One of its primary uses is in the early stages of nodes booting from a
+local area network. TFTP has been used for this application because it is very
+simple to implement.
+
+Example
+^^^^^^^
+
+.. code-block:: sh
+
+  # If you want to enable uploads, else TFTP server will act as read-only (optional)
+  set service tftp-server allow-upload
+
+  # Directory for TFTP server content
+  set service tftp-server directory '/config/tftpboot'
+
+  # On which addresses we want to listen for incoming TFTP connections? (mandatory)
+  set service tftp-server listen-address '2001:db8:ffee::1'
+  set service tftp-server listen-address '10.10.1.1'
+
+.. note:: Choose your ``directory`` location carefully or you will loose the
+   content on image upgrades. Any directory under ``/config`` is save at this
+   will be migrated.
+
+.. note:: Configuring a listen-address is essential for the service to work.
+
+The resulting configuration will look like:
+
+.. code-block:: sh
+
+  vyos@vyos# show service
+   tftp-server {
+      allow-upload
+      directory /config/tftpboot
+      listen-address 2001:db8:ffee::1
+      listen-address 10.10.1.1
+   }
+
 .. _ddclient: http://sourceforge.net/p/ddclient/wiki/Home/
 .. _RFC2136: https://www.ietf.org/rfc/rfc2136.txt
 .. _`Multicast DNS`: https://en.wikipedia.org/wiki/Multicast_DNS
@@ -1059,3 +1101,4 @@ After commit the resulting configuration will look like:
 .. _SNMPv2: https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol#Version_2
 .. _SNMPv3: https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol#Version_3
 .. _MIB: https://en.wikipedia.org/wiki/Management_information_base
+.. _TFTP: https://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocol