Prerequisites

System Requirements

• Linux distribution (Ubuntu 20.04+ recommended) or WSL2 on Windows
• At least 4GB RAM (8GB+ recommended)
• 20GB+ free disk space
• Internet connection

Required Packages (Ubuntu/Debian)

sudo apt update
sudo apt install build-essential ccache ecj fastjar file g++ gawk \
gettext git java-propose-classpath libelf-dev libncurses5-dev \
libncursesw5-dev libssl-dev python3 python3-distutils python3-setuptools \
python3-dev rsync subversion swig time unzip wget xsltproc zlib1g-dev

Step 1: Clone OpenWrt Source Code

# Clone the latest stable release (24.10.x)
git clone https://github.com/openwrt/openwrt.git
cd openwrt

# Or clone specific version
git clone -b v24.10.2 https://github.com/openwrt/openwrt.git
cd openwrt

Step 2: Update Feeds

# Update package feeds
./scripts/feeds update -a

# Install all available packages
./scripts/feeds install -a

Step 3: Configure Build

# Start configuration menu
make menuconfig

Essential Configuration Options:

Target System Selection:

• Target System: Select your target (e.g., Qualcomm Atheros IPQ40xx, MediaTek MT7621, etc.)
• Subtarget: Choose specific variant(e.g., generic)
• Target Profile: Select your device model

Basic Settings:

• Target Images: Enable “squashfs” and “ext4” if needed
• Kernel modules: Select required modules
• LuCI: Web interface (optional)
• Network: Basic networking packages

Common Device Examples:

• OpenWrt One: Target System → MediaTek ARM → Filogic 8×0 (MT798x) → OpenWrt One
• TP-Link Archer C7: Target System → Atheros ATH79 → Generic → TP-Link Archer C7
• Raspberry Pi: Target System → Broadcom BCM27xx → Raspberry Pi 4

Step 4: Build Configuration

Option 1: Use Default Configuration

# For specific device (example: TP-Link Archer C7)
make defconfig

Option 2: Use Pre-configured Profile

# List available profiles
make menuconfig

# Or use specific profile
make profile

Step 5: Start Compilation

First Time Build (Download Sources)

# Download all sources (this may take a while)
make download

# Start compilation
make -j$(nproc) V=s

Subsequent Builds

# Clean previous build
make clean

# Or clean everything
make dirclean

# Rebuild
make -j$(nproc) V=s

Step 6: Monitor Build Process

Build Output Location:

• Firmware files: bin/targets/[target]/[subtarget]/

Common Build Issues:

1. Download failures: Run make download again
2. Memory issues: Reduce parallel jobs: make -j2 V=s
3. Disk space: Ensure 10GB+ free space

Step 7: Locate Firmware Files

After successful compilation, firmware files will be in:

# Navigate to firmware directory
cd bin/targets/[target]/[subtarget]/

# List available firmware files
ls -la *.bin *.img *.tar

Common Firmware File Types:

• openwrt-[target]-[subtarget]-[device]-squashfs-factory.bin – Factory firmware
• openwrt-[target]-[subtarget]-[device]-squashfs-sysupgrade.bin – Upgrade firmware
• openwrt-[target]-[subtarget]-[device]-ext4-factory.img.gz – Ext4 factory image
• openwrt-[target]-[subtarget]-[device]-ext4-sysupgrade.img.gz – Ext4 upgrade image

Step 8: Flash Firmware

Via Web Interface (if upgrading existing OpenWrt):

1. Access router’s web interface (usually 192.168.1.1)
2. Go to System → Backup/Flash Firmware
3. Upload the *-sysupgrade.bin file
4. Click “Flash image”

Build Optimization Tips

Speed Up Builds:

# Use ccache for faster recompilation
export USE_CCACHE=1
export CCACHE_DIR=~/.ccache

# Use multiple CPU cores
make -j$(nproc) V=s

# Skip download step if sources exist
make -j$(nproc) V=s

Reduce Build Size:

# In menuconfig, disable unnecessary packages
# Remove LuCI if not needed
# Disable unused kernel modules
# Use squashfs instead of ext4 for smaller images

Troubleshooting

Common Errors:

1. “No rule to make target”: Run make defconfig first
2. Download failures: Check internet connection and run make download
3. Build failures: Check system requirements and dependencies
4. Memory errors: Reduce parallel jobs or increase swap space

Debug Build:

# Verbose output for debugging
make V=99

# Check specific package build
make package/[package-name]/compile V=s