This will automatically flash your Sonoff (DIY enabled) devices to a custom firmware of your choice.
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Automatic flashing of sonoff devices with custom firmware
Example run: docker run --rm --privileged -e DEBUGLEVEL=1 --net=host -e MODE=flash -e INTERFACE=wlp2s0 -v $PWD:/firmware/ dlbogdan/sonoff-auto-flasher
docker pull dlbogdan/sonoff-auto-flasher