# Build and pave quickstart

This document shows you how to build and deploy Fuchsia on a target device with
`fx` development commands. Most of these commands have additional commands, see
`fx help <command>` for details.

## Determine USB drive device path {#usb-drive-device-path}

Before you attempt to build and pave Fuchsia on a target device, you need to
know the path of your USB drive.

Note: For either operating system, you can run the command once with the USB
drive disconnected, then run again with the USB drive connected, to see the
difference.

### fx

To determine the correct path to your USB drive:

Note: The `fx` tool is platform agnostic and lists available USB drives.

```posix-terminal
fx mkzedboot
```

### Linux

To determine the correct path to your USB drive:

```posix-terminal
sudo fdisk -l
```

Drives are usually in the form `/dev/sd[x]` such as `/dev/sdc`.

Make sure that you select the drive rather than a specific partition. For
example, a specific partition has a number at the end of the path such as
`/dev/sdc1`.

### macOS

To determine the correct path to your USB drive:

```posix-terminal
diskutil list | grep external
```

Drives are usually in the form `/dev/disk[n]` such as `/dev/disk2`.

Note: If you see `ERROR: Can't open /dev/disk[n]: Resource busy` then you will
have to unmount the USB drive. To do this, run:

```posix-terminal
hdiutil unmount /dev/disk[n]
```

If this does not fix the error, try reformatting the drive:

```posix-terminal
diskutil eraseDisk JHFSX <name_of_the_usb_stick> /dev/disk[n]
```

## Build and deploy Fuchsia

To perform an initial build and deploy of Fuchsia with `fx`, do the following:

1.  Set your build type:

    Note: 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.

    ```posix-terminal
    fx set core.x64
    ```

1.  Build a Fuchsia image:

    ```posix-terminal
    fx build
    ```

    This command builds Zircon and then the rest of Fuchsia.

1.  Build the Zedboot media and install to a USB device target:

    Note: For information on obtaining the USB drive device path, see
    [USB drive device path](#usb-drive-device-path).

    ```posix-terminal
    fx mkzedboot <usb_drive_device_path>
    ```

1.  Attach Zedboot USB drive to your target device and reboot that device.

1.  On your target device, run:

    ```posix-terminal
    lsblk
    ```

1.  Take note of the HDD or SSD's device path from the output of `lsblk`. An
    example path looks like `/dev/sys/platform/pci/00:17.0/ahci/sata0/block`.

1.  On your target device, run:

    ```posix-terminal
    install-disk-image init-partition-tables --block-device <BLOCK_DEVICE_PATH>
    ```

1.  To start the bootserver, from your host, run:

    Note: The bootserver connects to the target device to upload the Fuchsia
    image and then paves your target device.

    ```posix-terminal
    fx pave
    ```

## Rebuild and redeploy Fuchsia

To rebuild and redeploy with `fx`:

1.  Ensure that HEAD is in a good state to pull at the
    [build dashboard](https://luci-milo.appspot.com/p/fuchsia).
1.  Fetch the latest code:

    ```posix-terminal
    jiri update
    ```

1.  Build a Fuchsia image:

    ```posix-terminal
    fx build
    ```

    This command builds Zircon and then the rest of Fuchsia.

1.  (Only for macOS users) Set up firewall rules:

    ```posix-terminal
    fx setup-macos
    ```

1.  From your host, start a development package server:

    ```posix-terminal
    fx serve
    ```

1.  Boot your target device without the Zedboot USB attached.

1.  From your host, push updated Fuchsia packages to the target device:

    ```posix-terminal
    fx ota
    ```

    In some cases, if `fx ota` does not complete successfully, consider repaving
    with `fx pave`.

## Troubleshooting

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

    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.

    To check the value of your `PATH` variable:

    ```posix-terminal
    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 `.`.