Does anyone know how I can make eth0 initialise on boot rather than having to manually run 'ifup eth0'?
why not just edit /etc/metwork/interfaces and uncomment '#auto eth0 dhcp' to read 'auto eth0 dhcp' ?
You can also add ip=dhcp or ip=xx.xx.xx.xx to your kernel boot parameters. You need to ensure that the kernel has dhcp etc compiled into it.
Beware that if you used dhcp, the kernel will wait until it has an IP address before finishing to boot.
Maybe the topic starter means having ethernet enabled in u-boot? I'm not sure if this is possible for Olinuxino u-boot. My Guruplug can do this and have images sent over tftp.