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Making it easy for u-boot to find uImage and uinitrd

I often fiddle with testing root images, kernels and initrd on my kirkwood based systems by using usb flash sticks. I found that although Jeff did a brilliant job on uboot his default environment was unable to directly boot all my testing images.

I made myself a custom environment that was more flexible and allowed me to boot from any usb port as long as the following limitations are met:

  • the kernel must be called uImage or must be linked with that name
  • the initrd must be called uinitrd or must be linked with that name
  • uImage and uinitrd must be contained in the first 4 detected usb devices
  • uImage and uinitrd must be in the root or in a boot sub-directory in the device that holds them
  • the root filesystem bust be labelled “root” and should possibly be ext3 formatted

Heres the environment dumped from fw_printenv: (taken from my GoFlexNet)

arcNumber=<put here your device's correct arcNumber>
boot_flash_kernel=nand read $flash_kernel_load_addr $flash_kernel_offest $flash_kernel_size; bootm $flash_kernel_load_addr
bootargs=console=ttyS0,115200 mtdparts=orion_nand:1M(u-boot),4M(uImage),32M(rootfs),-(data) root=/dev/sda2 ro rootfstype=ext2
bootcmd=run usb_scan; run set_flash_bootargs; run boot_flash_kernel
ethaddr=<put here your mac address>
led_error=orange blinking
led_exit=green off
led_init=green blinking
sb_scan_1=usb=0:2 dev=sda2
set_flash_bootargs=setenv bootargs ${console} ${mtdparts} ${flash_root_fs} ro ${flash_root_fstype}
set_usb_bootargs=setenv bootargs ${console} ${mtdparts} ${root_fs} ro ${root_fstype}
usb_boot_6=setenv root_fs root=/dev/sdg${usb_dev_part}
usb_dev_list=3 2 1 0
usb_part_list=4 3 2 1
usb_scan=usb start; setenv usb_boot_dev none; for dev in  $usb_dev_list; do test $dev -eq 0 && setenv devname /dev/sda ; test $dev -eq 1 &&  setenv devname /dev/sdb ; test $dev -eq 2 && setenv devname /dev/sdc ; test $dev -eq 3 && setenv devname /dev/sdd ; echo $devname ; for part in $usb_part_list; do echo $dev $part ; if ext2load usb ${dev}:$part 0x800000 /boot/uImage 10 ; then setenv usb_boot_dev $dev:$part ; setenv usb_boot_dir /boot ; fi  ; if ext2load usb ${dev}:$part 0x800000 /uImage 10 ; then setenv usb_boot_dev $dev:$part ; setenv usb_boot_dir ; fi  ; done; done; if test "$usb_boot_dev" = "none" ; then echo "No USB bootable device found" ; else echo "USB device $usb_boot_dev is bootable" ; setenv bootargs $console $mtdparts $root_fs ro $rootfstype ; echo $bootargs ; sleep 1; ext2load usb $usb_boot_dev 0x800000 $usb_boot_dir/uImage && setenv usb_boot_address 0x800000 ; ext2load usb $usb_boot_dev 0x1100000 $usb_boot_dir/uinitrd && setenv usb_boot_address 0x800000 0x1100000 ; bootm $usb_boot_address ; fi;

Labeling the root filesystem was a workaround when I started getting issues on device namings changes as I began using the SATA drives for NAS storage. In practice what was happening was that uboot thought that root was on sda but once the kernel booted it would detect the SATA drives before that and name the usb memory stick to after the last SATA drive causing a kernel panic as initrd attempts to mount the root filesystem. I thus changed the u-boot environment to pass the root device as a label rather then a device path. This allows me to boot my GoFlexNet correctly from any usb stick (even trough a usb hub) regardless of the presence of the SATA drives.


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