# Compilation and Building \(for Mini and Small Systems\)
- [Introduction](#section11660541593)
- [Directory Structure](#section161941989596)
- [Usage](#section1312121216216)
- [Usage Guidelines](#section129654513264)
- [Repositories Involved](#section1371113476307)
## Introduction
The compilation and building subsystem is a build framework based on Generate Ninja \(GN\) and Ninja, which supports component-based OpenHarmony development. This subsystem can be used to:
- Build products.
- Build chipset vendor components independently.
- Build a single component independently.
It is considered best practice to learn the following basic concepts before you start development and build:
- **Component**
A component is a reusable software unit that can contain source code, configuration files, resource files, and build scripts.
- **GN**
GN is short for Generate Ninja, which is a build system used to generate Ninja files.
- **Ninja**
Ninja is a small high-speed build system.
**Build Process**
The following figure shows the build process.
**Figure 1** Build process
1. **hb set**: Set the OpenHarmony source code directory and the product to build.
2. **hb build**: Build the product, development board, or component. The process to build the solution is as follows:
- **Reading configuration**: Read the development board configuration, which covers the toolchain, linking commands, and build options.
- **Running gn**: Run the **gn gen** command to read the product configuration \(related to the development board, kernel, and system components\) and generate the **out** directory and **ninja** files for the solution.
- **Running Ninja**: Run **ninja -C out/company/product** to start build.
- **Packaging**: Package the build result to create a file system image.
## Directory Structure
```
build/lite # Primary directory
├── components # Component description file
├── hb # hb pip installation package
├── make_rootfs # make script for the file system
├── config # Build configuration items
│ ├── component # Definitions of component-related templates, including static libraries, dynamic libraries, extension components, and emulator libraries
│ ├── kernel # Build configuration parameters of the kernel
│ └── subsystem # Subsystem template
├── ndk # NDK-related build scripts and configuration parameters
└── toolchain # Build toolchain, which contain the compiler directories, build options, and linking options
```
## Usage
### Usage Guidelines
1. **Prerequisites**
- Server and OS version: Linux server running 64-bit Ubuntu 16.04 or later
- Python version: 3.7.4 or later
- Repository: **build\_lite** of OpenHarmony source code
2. **Installing hb**
- Run the following command in the root directory of the source code:
```
python3 -m pip install --user build/lite
```
- Run the **hb -h** command. If the following information is displayed, the installation is successful:
```
usage: hb
OHOS build system
positional arguments:
{build,set,env,clean}
build Build source code
set OHOS build settings
env Show OHOS build env
clean Clean output
optional arguments:
-h, --help Show this help message and exit
```
- **Uninstalling hb**
Run the following command to uninstall hb:
```
python3 -m pip uninstall ohos-build
```
3. **Build Commands**
1. **hb set**
```
hb set -h
usage: hb set [-h] [-root [ROOT_PATH]] [-p]
optional arguments:
-h, --help Show this help message and exit.
-root [ROOT_PATH], --root_path [ROOT_PATH]
Set OHOS root path.
-p, --product Set OHOS board and kernel.
```
- If you run **hb set** with no argument, the default setting process starts.
- You can run **hb set -root** _\[ROOT\_PATH\]_ to set the root directory of the source code.
- **hb set -p --product** is used to set the product to build.
2. **hb env**
View the current configuration.
```
hb env
[OHOS INFO] root path: xxx
[OHOS INFO] board: hispark_taurus
[OHOS INFO] kernel: liteos
[OHOS INFO] product: ipcamera
[OHOS INFO] product path: xxx/vendor/hisilicon/ipcamera
[OHOS INFO] device path: xxx/device/hisilicon/hispark_taurus/sdk_linux_4.19
```
3. **hb build**
```
hb build -h
usage: hb build [-h] [-b BUILD_TYPE] [-c COMPILER] [-t [TEST [TEST ...]]]
[--dmverity] [-p PRODUCT] [-f] [-n]
[component [component ...]]
positional arguments:
component Name of the component.
optional arguments:
-h, --help Show this help message and exit.
-b BUILD_TYPE, --build_type BUILD_TYPE
Release or debug version.
-c COMPILER, --compiler COMPILER
Specify compiler.
-t [TEST [TEST ...]], --test [TEST [TEST ...]]
Compile test suit.
--dmverity Enable dmverity.
-p PRODUCT, --product PRODUCT
Build a specified product with
{product_name}@{company}, eg: ipcamera@hisilcon.
-f, --full Full code compilation.
-T [TARGET [TARGET ...]], --target [TARGET [TARGET ...]]
Compile single target
```
- If you run **hb build** with no argument, the previously configured code directory, product, and options are used for build.
- You can run **hb build** _\{component\}_ to build product components separately based on the development board and kernel set for the product, for example, **hb build kv\_store**.
- You can run **hb build -p PRODUCT** to skip the setting step and build the product directly.
- You can run **hb build** in **device/device\_company/board** to select the kernel and start build based on the current development board and the selected kernel to generate an image that contains the kernel and driver only.
4. **hb clean**
Clear the build result of the product in the **out** directory, and leave the **args.gn** and **build.log** files only. To clear files in a specified directory, add the directory parameter to the command, for example, **hb clean** _xxx_**/out/**_xxx_.
```
hb clean
usage: hb clean [-h] [out_path]
positional arguments:
out_path Clean a specified path.
optional arguments:
-h, --help Show this help message and exit.
```
## Repositories Involved
Compilation and building subsystem
**[build\_lite](https://gitee.com/openharmony/build_lite)**