Boot Linux over network

A bit of background

During development of Linux distribution it’s beneficial to load entire software over network. That removes the need for frequent and time-consuming writes to storage device.

Prerequisites

  1. Distribution files

    • device tree - system.dtb

    • Linux kernel image - Image

    • Root file system wrapped in U-Boot headers - rootfs.cpio.gz.u-boot

Steps

  1. Copy files to TFTP root on EGSE Host

    user@local-machine:~$ scp system.dtb egse-<id>.egse.vpn.sml.kplabs.space:/var/tftp
user@local-machine:~$ scp Image egse-<id>.egse.vpn.sml.kplabs.space:/var/tftp
user@local-machine:~$ scp rootfs.cpio.gz.u-boot egse-<id>.egse.vpn.sml.kplabs.space:/var/tftp

  2. Power on the device and stop in U-Boot shell

    U-Boot 2023.01 (Sep 21 2023 - 11:02:37 +0000)

CPU:   ZynqMP
Silicon: v3
Chip:  zu9eg
Board: Xilinx ZynqMP
DRAM:  2 GiB (effective 16 GiB)
PMUFW:  v1.1
PMUFW:  No permission to change config object
EL Level:       EL2
Secure Boot:    not authenticated, not encrypted
Core:  46 devices, 27 uclasses, devicetree: board
MMC:   mmc@ff170000: 0
Loading Environment from SPIFlash... SF: Detected s25fl512s with page size 256 Bytes, erase size 256 KiB, total 64 MiB
*** Warning - bad CRC, using default environment

In:    serial
Out:   serial
Err:   serial
Bootmode: QSPI_MODE
Reset reason:   EXTERNAL
Net:
ZYNQ GEM: ff0d0000, mdio bus ff0d0000, phyaddr 0, interface rgmii-id
eth0: ethernet@ff0d0000
scanning bus for devices...
SATA link 0 timeout.
SATA link 1 timeout.
AHCI 0001.0301 32 slots 2 ports 6 Gbps 0x3 impl SATA mode
flags: 64bit ncq pm clo only pmp fbss pio slum part ccc apst
starting USB...
No working controllers found
Hit any key to stop autoboot:  0
ZynqMP>

  3. Obtain IP address

    ZynqMP> dhcp
BOOTP broadcast 1
DHCP client bound to address 172.20.200.100 (37 ms)

  4. Download device tree

    ZynqMP> tftpboot ${fdt_addr_r} system.dtb
Using ethernet@ff0d0000 device
TFTP from server 172.20.200.1; our IP address is 172.20.200.100
Filename 'system.dtb'.
Load address: 0x40000000
Loading: ###
         6.3 MiB/s
done
Bytes transferred = 39583 (9a9f hex)

  5. Download root file system

    ZynqMP> tftpboot ${ramdisk_addr_r} rootfs.cpio.gz.u-boot
Using ethernet@ff0d0000 device
TFTP from server 172.20.200.1; our IP address is 172.20.200.100
Filename 'rootfs.cpio.gz.u-boot'.
Load address: 0x2100000
Loading: #################################################################
         #################################################################
         #################################################################
         #################################################################
         16.6 MiB/s
done
Bytes transferred = 38257813 (247c495 hex)

  6. Download Linux kernel image

    ZynqMP> tftpboot ${kernel_addr_r} Image
Using ethernet@ff0d0000 device
TFTP from server 172.20.200.1; our IP address is 172.20.200.100
Filename 'Image'.
Load address: 0x18000000
Loading: #################################################################
         #################################################################
         #################################################################
         #################################################################
         16.4 MiB/s
done
Bytes transferred = 21379584 (1463a00 hex)

  7. Boot Linux

    ZynqMP> booti ${kernel_addr_r} ${ramdisk_addr_r} ${fdt_addr_r}
## Loading init Ramdisk from Legacy Image at 02100000 ...
   Image Name:   dpu-leopard-leopard-dpu.rootfs-2
   Created:      2011-04-05  23:00:00 UTC
   Image Type:   AArch64 Linux RAMDisk Image (uncompressed)
   Data Size:    38257749 Bytes = 36.5 MiB
   Load Address: 00000000
   Entry Point:  00000000
   Verifying Checksum ... OK
## Flattened Device Tree blob at 40000000
   Booting using the fdt blob at 0x40000000
Working FDT set to 40000000
   Loading Ramdisk to 7973f000, end 7bbbb455 ... OK
   Loading Device Tree to 0000000079732000, end 000000007973ea9e ... OK
Working FDT set to 79732000

Starting kernel ...

[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034]
[    0.000000] Linux version 6.1.30-xilinx-v2023.2 (oe-user@oe-host) (aarch64-oe-linux-gcc (GCC) 13.2.0, GNU ld (GNU Binutils) 2.41.0.20231213) #1 SMP Fri Sep 22 10:41:01 UTC 2023
[    0.000000] Machine model: xlnx,zynqmp
[    0.000000] earlycon: cdns0 at MMIO 0x00000000ff000000 (options '115200n8')
...

KP Labs DPU 1.0 leopard-dpu ttyPS0

leopard-dpu login:

Summary

To boot Linux, you have to download three files from EGSE Host: kernel, root file system and device tree. U-Boot provides commands to download them over TFTP along with set of variables with memory addresses to store them. After downloading, you can boot Linux using booti command with addresses of kernel, root file system and device tree.