# Update from a file on the device From the Nerves application project directory, build the firmware. ``` MIX_TARGET= mix firmware ``` Connect to the device with SFTP and transfer the firmware bundle (`.fw`) onto the device. Modify the lines below to match your project. ``` sftp cd /data lcd _build/_dev/nerves/images/ lls put .fw quit ``` Connect to the device's console and run `fwup` from IEx to apply the firmware update. Reboot once the update is complete. The device will come back up with the new firmware running. ```elixir cmd "fwup -a -t upgrade -d /dev/ -i /data/.fw" reboot ``` The firmware bundle can be removed from the device if it is no longer needed. ```elixir File.rm "/data/.fw" ``` > 🛈 Tip > > `scp` is an alternative to `sftp`. However, on some systems `scp` responds with `lost connection` and fails to transfer the file. The tool used for the file transfer is not important as long as the firmware file makes it onto the device. ## Finding the disk The fwup `-d` flag specifies the disk to apply the update to. This is documented by the `NERVES_FW_DEVPATH` property in your Nerves system fwup config. If you need to find the disk without being able to reference the config, run fwup on the device without the `-d` flag. ```elixir cmd "fwup -a -t upgrade -i /data/.fw" ``` This will attempt to auto-detect the disk and will print what it has discovered. However, the console will hang when doing so. ``` Use 7.95 GB memory card found at /dev/mmcblk0? [y/N] ``` Break out of the command with Ctrl+C. Copy the path to the disk and paste it after the `-d` flag in the full fwup command above. ## Background A Nerves device doesn't have to receive a firmware update command remotely. [fwup](https://github.com/fwup-home/fwup?tab=readme-ov-file#overview) is used to manage firmware updates, and can be run directly on a Nerves device. This is actually how the OTA update process works under the hood. In this runbook we manually place a firmware file on the device, and then call `fwup` on the device to perform the firmware update. Once the device is rebooted, it will come up with the new firmware. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://nerves.redwirelabs.com/runbooks/update_from_file_on_device.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.