Updating the firmware/Cold Flashing

Cold flashing (N900)
If the bootloader is deleted/destroyed with dd, then it is possible to recover it with a cold flash, get the COMBINED image and extract it. flasher-3.5 -F image.bin -u

Run the following command for 2101 hardware revisions: flasher-3.5 -c -h RX-51:2101 -2 2nd.bin-RX-51\:2101\,2102\,2103 -s secondary.bin-RX-51\:2101\,2102\,2103 -S usb

You will see output similar to this: flasher v2.5.2 (Oct 21 2009) Using serial port usb Suitable USB device not found, waiting. USB device found found at bus 005, device address 004. Waiting for ASIC id... Got 69 bytes. ASIC ID: 05 01 05 01 34 30 07 57 13 02 01 00 12 15 01 3f 8f 41 14 07 41 48 49 d9 b5 94 4b 98 89 00 fb df 40 a2 89 14 15 01 87 3b  4d cd ca f5 44 4d 24 ec b2 ac 95 53 88 41 4f ab  cd 66 15 09 01 f7 48 8f 28 a0 27 e5 b3 Sending 2nd image (14720 bytes)... done. Sending ping... timeout! failed. Sending ping... pong. Sending secondary (109440 bytes)... done.

This should boot up the N900 with a temporary bootloader, proceed to flash the device with the commands above this section.

Thanks to jacekowski for the above explanation.