Using sysupgrade to upgrade firmware

Login to Carambola and download binary image to RAM. (Alter IP and path to match your binary image location)

scp test@192.168.0.105:/home/test/carambola/bin/ramips/openwrt-ramips-rt305x-carambola-squashfs-sysupgrade.bin /tmp

Perform upgrade procedure.

sysupgrade -v -n /tmp/openwrt-ramips-rt305x-carambola-squashfs-sysupgrade.bin

Or if you wish to save configuration files:

etc/ethers
etc/config/wireless
etc/config/system
etc/config/network
etc/config/dropbear
etc/config/firewall
etc/config/dhcp
etc/dropbear/dropbear_rsa_host_key
etc/dropbear/dropbear_dss_host_key

type:

sysupgrade -v -c /tmp/openwrt-ramips-rt305x-carambola-squashfs-sysupgrade.bin