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Trivial File Transfer Protocol short tftp

The Trivial File Transfer Protocol is commonly used in booting from network. There is tftp support available in U-Boot, but it needs to be configured by the vendor. One of the biggest advantages of tftp over for example loading the image from an SD-Card or an attached USB thumb drive is the fact that we do not have to unplug, copy, unmount and re plug the memory device each time we are testing a new kernel, device tree or image. This may also be used in combination with NFS booting.

Shipping tftp in a Container

Due to the fact tftp is quite simple from an implementation point of view it is ideal for running in a container. This just needs two files and a working Docker runtime.

Dockerfile:

FROM alpine:latest
RUN apk add --update --no-cache \
    tftp-hpa
EXPOSE 69/udp
ENTRYPOINT ["in.tftpd"]
CMD ["-L", "--secure", "/var/tftpboot"]

docker-compose.yml:

version: '2'

services:
  server:
    build: .
    ports:
      - "69:69/udp"
    volumes:
      - /var/docker-volumes/tftpboot:/var/tftpboot:ro
    restart: unless-stopped

This will expose the content of /var/docker-volumes/tftpboot via tftp. In case you do prefer a different location adjust it accordingly.

To build and run the tftp service execute the following commands in the directory containing the Dockerfile and docker-compose.yml:

$ sudo mkdir -p /var/docker-volumes/tftpboot
$ sudo chown -R $(id -u):$(id -g) -R /var/docker-volumes/tftpboot
$ docker-compose up --build

After the initial set-up you can start the service by running this command in the directory containing the Dockerfile and docker-compose.yml:

$ docker-compose up

Direct installation of tftp on the host

Please check your Linux distribution for instructions how to install the tftp service.

Using tftp on the Target

As already mentioned tftp support needs to be enabled in U-Boot. Due to the fact tftp is network based it also requires wired Ethernet support for your board. This will not work over a wireless connection. In U-Boot two variables need to be defined:

g12a_u212_v1# setenv ipaddr 192.168.0.69
g12a_u212_v1# setenv serverip 192.168.0.1

You may want to safe those settings to not having to enter them every time you use tftp:

g12a_u212_v1#saveenv
Saving Environment to aml-storage...
mmc env offset: 0x4d400000
Writing to MMC(1)... done
g12a_u212_v1#

To transfer any file from the hosts tftp directory use the U-Boot tftp command.:

g12a_u212_v1#tftp ${dtb_mem_addr} meson-sm1-x96-max.dtb
Speed: 1000, full duplex
Using dwmac.ff3f0000 device
TFTP from server 192.168.0.1; our IP address is 192.168.0.69
Filename 'meson-sm1-x96-max.dtb'.
Load address: 0x1000000
Loading: ####
         8.9 MiB/s
done
Bytes transferred = 46443 (b56b hex)