There are essentially three ways to build your NodeMCU firmware: cloud build service, Docker image, dedicated Linux environment (possibly VM).

## Tools

### Cloud Build Service
NodeMCU "application developers" just need a ready-made firmware. There's a [cloud build service](https://nodemcu-build.com/) with a nice UI and configuration options for them.

### Docker Image
Occasional NodeMCU firmware hackers don't need full control over the complete tool chain. They might not want to setup a Linux VM with the build environment. Docker to the rescue. Give [Docker NodeMCU build](https://hub.docker.com/r/marcelstoer/nodemcu-build/) a try.

!!! caution

    Take note that you need to clone the repository including Git submodules just as described below for the Linux environment. 

### Linux Build Environment
NodeMCU firmware developers commit or contribute to the project on GitHub and might want to build their own full fledged build environment with the complete tool chain.

#### Build environment dependencies, tools and libraries:

#### Ubuntu:

```bash
sudo apt-get install -y gperf python-pip python-dev flex bison build-essential libssl-dev libffi-dev libncurses5-dev libncursesw5-dev libreadline-dev cmake
```

#### Setting up the repository

Run the following command for a new checkout from scratch. This will fetch the nodemcu repo, checkout the `dev-esp32` branch and finally pull all submodules:

```
git clone --branch dev-esp32 --recurse-submodules https://github.com/nodemcu/nodemcu-firmware.git nodemcu-firmware-esp32
```

To install the prerequisites for the ESP32 SDK and NodeMCU components, run:
```
./install.sh
```

The `make menuconfig` command initiates the build process, which will start with the configuration menu to set the build options.

!!! important

    GNU make version 4.0 or higher is required for a successful build. Versions 3.8.2 and below will produce an incomplete firmware image.

Updating your clone from upstream needs an additional command to update the submodules as well:

```
git pull origin dev-esp32
git submodule init #only if repo was cloned w/o submodules init
git submodule update --recursive
```

Here is a video walk through by John Lauer (ChiliPeppr) of building the firmware in Linux from scratch with a fresh install of Ubuntu 19 so you can see all of the dependencies needed to get your build completed and flashed to your ESP32 device.

[![Video walk through for Linux Build Environment](https://img.youtube.com/vi/x6CGECsioYg/0.jpg)](https://www.youtube.com/watch?v=x6CGECsioYg "Video walk through for Linux Build Environment")

## Build Options

All configuration options are accessed from the file `sdkconfig`. It's advisable to set it up with the interactive `make menuconfig` - on a fresh checkout you're prompted to run through it by default.

The most notable options are described in the following sections.

### Select Modules

Follow the menu path
```
Component config --->
  NodeMCU modules --->
```
Tick or untick modules as required.

### UART default bit rate

Follow the menu path
```
Component config --->
  Platform config --->
    UART console default bit rate --->
```

### CPU Frequency

Follow the menu path
```
Component config --->
  ESP32-specific --->
    CPU frequency --->
```

### Stack Size

If you experience random crashes then increase the stack size and feed back your observation on the project's issues list.

Follow the menu path
```
Component config --->
  ESP32-specific --->
    Main task stack size --->
```

### Flashing Options

Default settings for flashing the firmware with esptool.py are also configured with menuconfig:

```
Serial flasher config --->
  Default serial port
  Default baud rate
  Flash SPI mode --->
  Detect flash size when flashing bootloader --->
```

### Partition Table
IDF's default partition table `Single factory app, no OTA` does not provide enough room for a firmware including large modules like e.g. `http` or `sodium`. To enable full feature sets, NodeMCU uses a custom partition table from `components/platform/partitions.csv` which allocates ~1.5 MB for the firmware image. During first boot, the firmware creates an additional partition for SPIFFS in the remaining flash space.

For 2MB flash modules an alternative partition table available as `components/platform/partitions-2MB.csv`. It restricts the SPIFFS partition to  ~448 kB and can be used with menuconfig:

```
Partition Table --->
  Partition Table (Custom partition table CSV)
  (components/platform/partitions-2MB.csv) Custom partition CSV file
  (0x10000) Factory app partition offset
```