Build and flash Fuchsia

This document walks through how to build and flash a Fuchsia image on a hardware device using fx commands.

Note: For more information on these commands, run fx help <COMMAND>.

Identify USB drive device path {:#usb-drive-device-path .numbered}

Before you can build and flash Fuchsia on a target device, you first need to identify the path of your USB drive.

It is recommended to run the command below once with the USB drive disconnected, then run it again with the USB drive connected to see the difference.

{fx tool}
To check the correct path to your USB drive using the fx tool, run the following command:
```
fx mkzedboot
```
The fx tool is platform agnostic and lists available USB drives.
{Linux command}
To check the correct path to your USB drive using a Linux command, run the following command:
```
sudo fdisk -l
```

Drives are usually in the form /dev/sd* such as /dev/sdc. Make sure that you select the drive rather than a specific partition. Forexample, a specific partition has a number at the end of the path such as /dev/sdc1.

Build and flash Fuchsia {:#build-and-flash-fuchsia .numbered}

To perform an initial build and flash of a Fuchsia image using the fx tool, do the following:

Set your Fuchsia build configuration:
```
fx set core.x64
```
This configures the build to build the core product on a generic x64 board. For a list of available products and boards, see fx list-products and fx list-boards for lists of available products, respectively.
Build a Fuchsia image:
```
fx build
```
This command builds Zircon and then the rest of Fuchsia.
Build the Zedboot media and install to a USB device target:
```
fx mkzedboot <usb_drive_device_path>
```
For information on obtaining the USB drive device path, see USB drive device path.
Attach Zedboot USB drive to your target device and reboot that device.

On your target device, run:

install-disk-image init-partition-tables

From your host, start the bootserver:
```
fx flash
```
The bootserver connects to the target device to upload the Fuchsia image and then flashes your target device.

Rebuild and reflash Fuchsia {:#rebuild-and-reflash-fuchsia .numbered}

To re-deploy Fuchsia using the fx tool, do the following:

Ensure that HEAD is in a good state to pull at the build dashboard.
Fetch the latest code:
```
jiri update
```
Build a Fuchsia image:
```
fx build
```
This command builds Zircon and then the rest of Fuchsia.
From your host, start a development package server:
```
fx serve
```
Boot your target device without the Zedboot USB attached.
From your host, push updated Fuchsia packages to the target device:
```
fx ota
```
In some cases, if fx ota does not complete successfully, consider repaving with fx flash.

Troubleshooting

If fx build fails, make sure that your PATH environment variable is set correctly.

To check the value of your PATH variable:

echo $PATH

Make that sure that the output of your PATH variable is a list of directories separated by colons. Make sure that none of the directories are separated by a dot (.).

Note: The fx script changes the working directory in a way that may create conflicts between the commands it uses (such as touch) and the binaries in the working directory.