Create page for updating from a file on the device

pages/runbooks.md

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+---
+title: Runbooks
+layout: page
+has_children: true
+---
+
+# Runbooks

pages/runbooks/update_from_file_on_device.md

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+---
+title: Update from file on device
+layout: page
+parent: Runbooks
+---
+
+# Update from a file on the device
+
+From the Nerves application project directory, build the firmware.
+
+```text
+MIX_TARGET=<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.
+
+```text
+sftp <device ip address>
+cd /data
+lcd _build/<target>_dev/nerves/images/
+lls
+put <app>.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.
+
+```text
+cmd "fwup -a -t upgrade -d /dev/<disk> -i /data/<app>.fw"
+reboot
+```
+
+The firmware bundle can be removed from the device if it is no longer needed.
+
+```text
+File.rm "/data/<app>.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.
+
+```text
+cmd "fwup -a -t upgrade -i /data/<app>.fw"
+```
+
+This will attempt to auto-detect the disk and will print what it has discovered.
+However, the console will hang when doing so.
+
+```text
+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.