BusyBox for Embedded Systems

Single binary providing common Unix utilities for minimal systems.

Installation

# Install from package manager
apt-get install busybox-static

# Or download and compile
wget https://busybox.net/downloads/busybox-1.36.1.tar.bz2
tar xf busybox-1.36.1.tar.bz2
cd busybox-1.36.1

Configuration

# Default configuration (all applets)
make defconfig

# Minimal configuration
make allnoconfig

# Interactive configuration
make menuconfig

Key Configuration Options

# Enable static linking (recommended for initramfs)
CONFIG_STATIC=y

# Essential applets
CONFIG_ASH=y          # Shell
CONFIG_MOUNT=y        # Mount filesystems
CONFIG_UMOUNT=y       # Unmount filesystems
CONFIG_MKDIR=y        # Create directories
CONFIG_LS=y           # List files
CONFIG_CAT=y          # Display files
CONFIG_ECHO=y         # Print text
CONFIG_INIT=y         # Init system
CONFIG_SWITCH_ROOT=y  # Switch root filesystem

Building

# Build BusyBox
make -j$(nproc)

# Install to directory
make CONFIG_PREFIX=/path/to/initramfs install

Symlink Installation

BusyBox uses symlinks for applets:

# Manual symlink creation
cd initramfs/bin
ln -s busybox sh
ln -s busybox ls
ln -s busybox mount

# Or use --install flag
./busybox --install -s /path/to/initramfs/bin

Using as Init

Create /init using BusyBox shell:

#!/bin/busybox sh

/bin/busybox mount -t proc none /proc
/bin/busybox mount -t sysfs none /sys
/bin/busybox mount -t devtmpfs none /dev

exec /bin/busybox sh

Common Applets

Cross-Compilation

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j$(nproc)