TFTP (remote/network kernel) using U-Boot

Prerequisites

This tutorial assumes your host PC is running Ubuntu 14.04.1 LTS or later and is on the same local network as your development platform; for simplicity's sake we assume a DHCP server is available on the network, too.

If using Juno, ensure you are using the front ethernet port.

See this page for instructions on how to network mount a userspace filesystem using U-Boot.

Setting up a TFTP server

Install the following packages on your host PC:

$ sudo apt-get update && sudo apt-get install xinetd tftpd tftp

Create file `/etc/xinetd.d/tftp' with the following contents:

service tftp
{
     protocol = udp
     port = 69
     socket_type = dgram
     wait = yes
     user = nobody
     server = /usr/sbin/in.tftpd
     server_args = /tftpboot
     disable = no
}

Create directory `/tftpboot/' (this matches the `server-args' above) and set its permissions:

$ sudo mkdir /tftpboot/
$ sudo chmod -R 777 /tftpboot/
$ sudo chown -R nobody /tftpboot/

Restart the `xinetd' service:

$ sudo service xinetd restart

Test the server by creating a simple `test' file in `/tftpboot/':

$ cd /tftpboot/
$ echo "this is a test" > test
$ cat test
this is a test

Get the IP address of your host PC via `ifconfig', then from another system:

$ tftp <host_pc_ip_address>
tftp> get test
Sent 159 bytes in 0.0 seconds
tftp> quit
$ cat test
this is a test

After confirming that the TFTP server is working correctly, copy your kernel image, device tree blob, and ramdisk (where appropriate) to `/tftpboot/'. This example expects the paths to be as follows:

  • Kernel image: `/tftpboot/Image'
  • Device tree blob:`/tftpboot/juno/juno.dtb'

U-Boot TFTP

Power up the Juno board and interrupt U-Boot's default boot selection:

The default boot selection will start in   3 seconds

Save your host PC's IP address to the `serverip' environment variable:

VExpress64# set serverip <host_pc_ip_address>
VExpress64# saveenv

Next modify U-Boot's boot command to boot via TFTP:

VExpress64# set origbootcmd "$bootcmd"
VExpress64# set autoload no
VExpress64# set bootcmd "dhcp; tftp ${kernel_addr} ${serverip}:Image; tftp ${fdt_addr} ${serverip}:juno/juno.dtb; booti ${kernel_addr} - ${fdt_addr}"
VExpress64# saveenv

Reboot the Juno; it should now boot via TFTP.

This is a persistent change, i.e. the Juno will boot via TFTP on every power up. To revert back to the default boot behaviour:

VExpress64# set bootcmd "$origbootcmd"

UEFI TFTP

This section is not applicable from Linaro Release 16.02 onwards; the EDK-II based UEFI provided as part of the deliverables does not support TFTP boot. We've left this information here for legacy support.

First select the `Boot Manager' option:

[1] Linaro image in NOR Flash

        - VenHw(E7223039-5836-41E1-B542-D7EC736C5E59)/norkern
        - Arguments: dtb=board.dtb initrd=ramdisk.img console=ttyAMA0,115200 androidboot.hardware=juno systemd.log_target=null rootwait root=/dev/sda2 sky2.mac_address=0x04
-----------------------
FDT Device Paths
        - VenHw(E7223039-5836-41E1-B542-D7EC736C5E59)/r1a57.dtb
-----------------------
[2] Shell
[3] Boot Manager
[4] Reboot
[5] Shutdown
Start: 3

Select `Add Boot Device Entry':

[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Update FDT path
[5] Return to main menu
Choice: 1

Select `TFTP on MAC Address':

[1] Firmware Volume (0 MB)
        - MemoryMapped(0xB,0xE0000000,0xE00EFFFF)
[2] Firmware Volume (0 MB)
        - MemoryMapped(0xB,0xFE792000,0xFEBAED3F)
[3] NOR Flash (63 MB)
        - VenHw(E7223039-5836-41E1-B542-D7EC736C5E59)
[4] PXE on MAC Address: 00:02:F7:00:66:E3
        - MAC(0002F70066E3,0x1)
[5] TFTP on MAC Address: 00:02:F7:00:66:E3
        - MAC(0002F70066E3,0x1)
Select the Boot Device: 5

Enter each setting as shown below, where `<host_pc_ip_address>' is the IP address of your host PC in the form `aaa.bbb.ccc.ddd'. Note that in this example the filesystem is on a USB stick (`/dev/sda2').

Get the IP address from DHCP: [y/n] y
Get the TFTP server IP address: <host_pc_ip_address>
File path of the EFI Application or the kernel : Image
Is an EFI Application? [y/n] n
Has FDT support? [y/n] y
Add an initrd: [y/n] n
Arguments to pass to the binary: console=ttyAMA0,115200 earlyprintk=pl011,0x7ff80000 root=/dev/sda2 rootwait verbose debug
Description for this new Entry: TFTP boot example

Next update the FDT entry for the TFTP boot entry:

[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Update FDT path
[5] Return to main menu
Choice: 4
[1] Firmware Volume (0 MB)
        - MemoryMapped(0xB,0xE0000000,0xE00EFFFF)
[2] Firmware Volume (0 MB)
        - MemoryMapped(0xB,0xFE792000,0xFEBAED3F)
[3] NOR Flash (63 MB)
        - VenHw(E7223039-5836-41E1-B542-D7EC736C5E59)
[4] PXE on MAC Address: 00:02:F7:00:66:E3
        - MAC(0002F70066E3,0x1)
[5] TFTP on MAC Address: 00:02:F7:00:66:E3
        - MAC(0002F70066E3,0x1)
Select the Boot Device: 5
Get the IP address from DHCP: [y/n] y
Get the TFTP server IP address: <tftp server ip address>
File path of the FDT blob : juno/juno.dtb

Finally, return to the main menu and select the new `TFTP boot example' option:

[1] Add Boot Device Entry
[2] Update Boot Device Entry
[3] Remove Boot Device Entry
[4] Update FDT path
[5] Return to main menu
Choice: 5
[1] Linaro image in NOR Flash
        - VenHw(E7223039-5836-41E1-B542-D7EC736C5E59)/norkern
        - Arguments: dtb=board.dtb initrd=ramdisk.img console=ttyAMA0,115200 androidboot.hardware=juno systemd.log_target=null rootwait root=/dev/sda2 sky2.mac_address=0x04
[2] TFTP boot example
        - MAC(0002F70066E3,0x1)/IPv4(aaa.bbb.ccc.ddd)/Image
        - Arguments: console=ttyAMA0,115200 earlyprintk=pl011,0x7ff80000 root=/dev/sda2 rootwait verbose debug
        - LoaderType: Linux kernel with FDT support
-----------------------
FDT Device Paths
        - MAC(0002F70066E3,0x1)/IPv4(xxx.xxx.xxx.xxx)/juno/juno.dtb
-----------------------
[3] Shell
[4] Boot Manager
[5] Reboot
[6] Shutdown
Start: 2
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