Okay I solved it. Thank god. The all boot process was starting before U3 could detect the USB HDD.
Here is what I did if anyone is interested.
1. SSHed into working Arch installation on Odroid-U3 (MicroSD)
2. Made a file boot.txt with following contents in /boot
$this->bbcode_second_pass_code('', '
cd /boot/
nano boot.txt
')
$this->bbcode_second_pass_code('', '
setenv initrd_high "0xffffffff"
setenv fdt_high "0xffffffff"
setenv bootcmd "fatload mmc 0:1 0x40008000 zImage; fatload mmc 0:1 0x42000000 uInitrd; bootm 0x40008000 0x42000000"
setenv bootargs "console=tty1 console=ttySAC1,115200n8 root=/dev/sda2 rootwait"
set bootdelay 4
save
boot
')
3. Made boot.scr with mkimage command
$this->bbcode_second_pass_code('', '
mkimage -T script -A arm -C none -n 'Custom Boot Script for U3' -d boot.txt boot.scr
')
4. Connected my USB HDD to Odroid-U3.
5. Formatted /dev/sda2 with ext4
$this->bbcode_second_pass_code('', '
mkfs.ext4 -L ArchARM /dev/sda2
')
6. Mounted /dev/sda2 to /mnt/sad2
$this->bbcode_second_pass_code('', '
mkdir /mnt/sda2
mount /dev/sda2 /mnt/sda2
')
7. Rsynced root of MicroSD to /dev/sda2 (TIP: Arch Wiki)
$this->bbcode_second_pass_code('', '
rsync -aAXv --progress --verbose --delete /* /mnt/sda2/ --exclude={/dev/*,/proc/*,/sys/*,/tmp/*,/run/*,/mnt/*,/media/*,/lost+found}
')
8. Rebooted
$this->bbcode_second_pass_code('', '
systemctl reboot
')
After login you can check with df -h what is your root partiton
TIP: You may need to install uboot-mkimage and rsync to use these steps
$this->bbcode_second_pass_code('', '
pacman -S uboot-mkimage rsync
')$this->bbcode_second_pass_quote('', 'S')ources & Help:
1.
http://odroid.us/mediawiki/index.php?ti ... _USB_Drive2.
https://wiki.archlinux.org/index.php/Fu ... with_rsync