Build Custom ROM from Source

Ready to go beyond flashing and start building? Compiling Android from source is the ultimate customization - you control every line of code.

Fair warning: this is advanced territory. But if you've always been curious how those ROMs are made, this guide is for you.

Requirements

Hardware

Minimum specs for building Android:

RAM: 16GB minimum (32GB+ recommended)
CPU: 4+ cores (8+ recommended)
Storage: 300GB+ free space (SSD strongly recommended)
Internet: Fast connection for downloading 50GB+ sources

Software

OS: Ubuntu 20.04+ or other compatible Linux distro
Patience: First sync can take hours

Step 1: Set Up Build Environment

Install Ubuntu Dependencies

sudo apt update
sudo apt install bc bison build-essential ccache curl flex \
g++-multilib gcc-multilib git gnupg gperf imagemagick lib32ncurses5-dev \
lib32readline-dev lib32z1-dev liblz4-tool libncurses5 libncurses5-dev \
libsdl1.2-dev libssl-dev libxml2 libxml2-utils lzop pngcrush rsync \
schedtool squashfs-tools xsltproc zip zlib1g-dev openjdk-11-jdk python3

Install Repo Tool

Google's repo tool manages multiple git repositories:

mkdir -p ~/bin
curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
chmod a+x ~/bin/repo

# Add to PATH
echo 'export PATH=~/bin:$PATH' >> ~/.bashrc
source ~/.bashrc

Configure Git

git config --global user.name "Your Name"
git config --global user.email "your@email.com"

Set Up ccache

ccache dramatically speeds up rebuilds:

echo 'export USE_CCACHE=1' >> ~/.bashrc
echo 'export CCACHE_EXEC=/usr/bin/ccache' >> ~/.bashrc
source ~/.bashrc

# Set cache size (50GB recommended)
ccache -M 50G

Step 2: Initialize Repository

Create Build Directory

mkdir -p ~/android/lineage
cd ~/android/lineage

Initialize Repo

For LineageOS 21 (Android 14):

repo init -u https://github.com/LineageOS/android.git -b lineage-21.0 --git-lfs

For AOSP:

repo init -u https://android.googlesource.com/platform/manifest -b android-14.0.0_r1

Step 3: Sync Source Code

This downloads ~50GB of source code:

repo sync -c --force-sync --no-clone-bundle --no-tags -j$(nproc --all)

Flags explained:

-c: Only sync current branch
-j$(nproc --all): Use all CPU cores
First sync: 1-4 hours depending on internet

If sync fails, just run again - it resumes.

Step 4: Add Device Trees

Required Repositories

To build for a device, you need:

Device tree: Device-specific configuration
Kernel source: Linux kernel for device
Vendor blobs: Proprietary files

Using Local Manifests

Create .repo/local_manifests/ folder:

mkdir -p .repo/local_manifests

Create manifest file (example for device "bacon"):

<?xml version="1.0" encoding="UTF-8"?>
<manifest>
  <project name="device_oneplus_bacon" 
           path="device/oneplus/bacon" 
           remote="github" 
           revision="lineage-21" />
  <project name="kernel_oneplus_bacon" 
           path="kernel/oneplus/bacon" 
           remote="github" />
  <project name="vendor_oneplus_bacon" 
           path="vendor/oneplus/bacon" 
           remote="github" />
</manifest>

Sync again to get device files:

repo sync -c --force-sync -j$(nproc --all)

Step 5: Configure Build

Set Up Environment

source build/envsetup.sh

Select Device

For LineageOS:

breakfast bacon
# or
lunch lineage_bacon-userdebug

For AOSP:

lunch aosp_walleye-userdebug

Build Types

Type	Purpose
user	Production, limited debugging
userdebug	Debug + user, most common
eng	Full debugging, slowest

Step 6: Build!

Start Build

mka bacon -j$(nproc --all)

For AOSP:

make -j$(nproc --all)

Build Time

Expect:

First build: 2-8 hours (depending on hardware)
Subsequent builds with ccache: 30min - 2 hours

Output

ROM zip appears in:

out/target/product/bacon/lineage-21.0-xxxxxxxx-UNOFFICIAL-bacon.zip

Making Modifications

Where to Make Changes

Change	Location
System apps	packages/apps/
Framework	frameworks/base/
System UI	frameworks/base/packages/SystemUI/
Settings	packages/apps/Settings/
Kernel	kernel/[vendor]/[device]/

Example: Add System Feature

Edit framework file:

nano frameworks/base/core/res/res/values/config.xml

Rebuild affected module:

mma SystemUI  # Rebuild SystemUI only

Or full rebuild:

mka bacon

Common Build Errors

"Jack server error"

# Kill existing jack server
./prebuilts/sdk/tools/jack-admin kill-server
./prebuilts/sdk/tools/jack-admin start-server

Out of Memory

# Limit jack memory
export JACK_SERVER_VM_ARGUMENTS="-Dfile.encoding=UTF-8 -XX:+TieredCompilation -Xmx4g"

Or reduce parallel jobs:

mka bacon -j4  # Instead of -j$(nproc)

Missing Dependencies

# Sync again
repo sync -c --force-sync
# Check local manifests

Speed Tips

Use SSD

HDD builds are painfully slow. SSD or NVMe makes huge difference.

ccache is Essential

After first build, ccache speeds up rebuilds dramatically:

ccache -s  # Check cache statistics

Parallel Jobs

Match to CPU cores, but consider RAM:

16GB RAM: -j4 to -j8
32GB RAM: -j8 to -j16
64GB+ RAM: -j$(nproc --all)

Build Server

Consider cloud build servers:

Google Cloud
AWS EC2
Dedicated build machines

Cleaning Builds

Clean Output

Remove built files (keep source):

make clean

Deep Clean

Remove all output:

make clobber

Remove ccache

ccache -C  # Clear cache

Create Release

Build final zip
Test thoroughly
Generate checksums:

sha256sum yourrom.zip > yourrom.zip.sha256

Publish

XDA Developers forum
GitHub releases
Telegram channels

Documentation

Include:

Changelog
Known issues
Installation instructions
Credits

Learning Path

Start Simple

Build existing ROM for your device
Make small changes, rebuild
Learn where everything is

Then Advance

Port ROM to new device
Create device trees
Fix device-specific bugs
Build custom kernel

Resources

LineageOS Wiki
AOSP documentation
XDA Developers forums
r/AndroidDev

Summary

Building ROM:
1. Set up Ubuntu with dependencies
2. Install repo tool
3. repo sync sources (~50GB)
4. Add device trees
5. source build/envsetup.sh
6. lunch device-userdebug
7. mka bacon
8. Wait...
9. ROM in out/target/

Building from source is rewarding. You understand Android deeply and can make any modification imaginable. Start the journey!

Keywords: build custom rom, compile android, lineageos build, aosp source, android development

Build Custom ROM from Source

Ready to go beyond flashing and start building? Compiling Android from source is the ultimate customization - you control every line of code.

Fair warning: this is advanced territory. But if you've always been curious how those ROMs are made, this guide is for you.

Requirements

Hardware

Minimum specs for building Android:

RAM: 16GB minimum (32GB+ recommended)
CPU: 4+ cores (8+ recommended)
Storage: 300GB+ free space (SSD strongly recommended)
Internet: Fast connection for downloading 50GB+ sources

Software

OS: Ubuntu 20.04+ or other compatible Linux distro
Patience: First sync can take hours

Step 1: Set Up Build Environment

Install Ubuntu Dependencies

sudo apt update
sudo apt install bc bison build-essential ccache curl flex \
g++-multilib gcc-multilib git gnupg gperf imagemagick lib32ncurses5-dev \
lib32readline-dev lib32z1-dev liblz4-tool libncurses5 libncurses5-dev \
libsdl1.2-dev libssl-dev libxml2 libxml2-utils lzop pngcrush rsync \
schedtool squashfs-tools xsltproc zip zlib1g-dev openjdk-11-jdk python3

Install Repo Tool

Google's repo tool manages multiple git repositories:

mkdir -p ~/bin
curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
chmod a+x ~/bin/repo

# Add to PATH
echo 'export PATH=~/bin:$PATH' >> ~/.bashrc
source ~/.bashrc

Configure Git

git config --global user.name "Your Name"
git config --global user.email "your@email.com"

Set Up ccache

ccache dramatically speeds up rebuilds:

echo 'export USE_CCACHE=1' >> ~/.bashrc
echo 'export CCACHE_EXEC=/usr/bin/ccache' >> ~/.bashrc
source ~/.bashrc

# Set cache size (50GB recommended)
ccache -M 50G

Step 2: Initialize Repository

Create Build Directory

mkdir -p ~/android/lineage
cd ~/android/lineage

Initialize Repo

For LineageOS 21 (Android 14):

repo init -u https://github.com/LineageOS/android.git -b lineage-21.0 --git-lfs

For AOSP:

repo init -u https://android.googlesource.com/platform/manifest -b android-14.0.0_r1

Step 3: Sync Source Code

This downloads ~50GB of source code:

repo sync -c --force-sync --no-clone-bundle --no-tags -j$(nproc --all)

Flags explained:

-c: Only sync current branch
-j$(nproc --all): Use all CPU cores
First sync: 1-4 hours depending on internet

If sync fails, just run again - it resumes.

Step 4: Add Device Trees

Required Repositories

To build for a device, you need:

Device tree: Device-specific configuration
Kernel source: Linux kernel for device
Vendor blobs: Proprietary files

Using Local Manifests

Create .repo/local_manifests/ folder:

mkdir -p .repo/local_manifests

Create manifest file (example for device "bacon"):

<?xml version="1.0" encoding="UTF-8"?>
<manifest>
  <project name="device_oneplus_bacon" 
           path="device/oneplus/bacon" 
           remote="github" 
           revision="lineage-21" />
  <project name="kernel_oneplus_bacon" 
           path="kernel/oneplus/bacon" 
           remote="github" />
  <project name="vendor_oneplus_bacon" 
           path="vendor/oneplus/bacon" 
           remote="github" />
</manifest>

Sync again to get device files:

repo sync -c --force-sync -j$(nproc --all)

Step 5: Configure Build

Set Up Environment

source build/envsetup.sh

Select Device

For LineageOS:

breakfast bacon
# or
lunch lineage_bacon-userdebug

For AOSP:

lunch aosp_walleye-userdebug

Build Types

Type	Purpose
user	Production, limited debugging
userdebug	Debug + user, most common
eng	Full debugging, slowest

Step 6: Build!

Start Build

mka bacon -j$(nproc --all)

For AOSP:

make -j$(nproc --all)

Build Time

Expect:

First build: 2-8 hours (depending on hardware)
Subsequent builds with ccache: 30min - 2 hours

Output

ROM zip appears in:

out/target/product/bacon/lineage-21.0-xxxxxxxx-UNOFFICIAL-bacon.zip

Making Modifications

Where to Make Changes

Change	Location
System apps	packages/apps/
Framework	frameworks/base/
System UI	frameworks/base/packages/SystemUI/
Settings	packages/apps/Settings/
Kernel	kernel/[vendor]/[device]/

Example: Add System Feature

Edit framework file:

nano frameworks/base/core/res/res/values/config.xml

Rebuild affected module:

mma SystemUI  # Rebuild SystemUI only

Or full rebuild:

mka bacon

Common Build Errors

"Jack server error"

# Kill existing jack server
./prebuilts/sdk/tools/jack-admin kill-server
./prebuilts/sdk/tools/jack-admin start-server

Out of Memory

# Limit jack memory
export JACK_SERVER_VM_ARGUMENTS="-Dfile.encoding=UTF-8 -XX:+TieredCompilation -Xmx4g"

Or reduce parallel jobs:

mka bacon -j4  # Instead of -j$(nproc)

Missing Dependencies

# Sync again
repo sync -c --force-sync
# Check local manifests

Speed Tips

Use SSD

HDD builds are painfully slow. SSD or NVMe makes huge difference.

ccache is Essential

After first build, ccache speeds up rebuilds dramatically:

ccache -s  # Check cache statistics

Parallel Jobs

Match to CPU cores, but consider RAM:

16GB RAM: -j4 to -j8
32GB RAM: -j8 to -j16
64GB+ RAM: -j$(nproc --all)

Build Server

Consider cloud build servers:

Google Cloud
AWS EC2
Dedicated build machines

Cleaning Builds

Clean Output

Remove built files (keep source):

make clean

Deep Clean

Remove all output:

make clobber

Remove ccache

ccache -C  # Clear cache

Create Release

Build final zip
Test thoroughly
Generate checksums:

sha256sum yourrom.zip > yourrom.zip.sha256

Publish

XDA Developers forum
GitHub releases
Telegram channels

Documentation

Include:

Changelog
Known issues
Installation instructions
Credits

Learning Path

Start Simple

Build existing ROM for your device
Make small changes, rebuild
Learn where everything is

Then Advance

Port ROM to new device
Create device trees
Fix device-specific bugs
Build custom kernel

Resources

LineageOS Wiki
AOSP documentation
XDA Developers forums
r/AndroidDev

Summary

Building ROM:
1. Set up Ubuntu with dependencies
2. Install repo tool
3. repo sync sources (~50GB)
4. Add device trees
5. source build/envsetup.sh
6. lunch device-userdebug
7. mka bacon
8. Wait...
9. ROM in out/target/

Building from source is rewarding. You understand Android deeply and can make any modification imaginable. Start the journey!

Keywords: build custom rom, compile android, lineageos build, aosp source, android development

Build Custom ROM from Source - Complete Developer Guide

Build Custom ROM from Source

Requirements

Hardware

Software

Step 1: Set Up Build Environment

Install Ubuntu Dependencies

Install Repo Tool

Configure Git

Set Up ccache

Step 2: Initialize Repository

Create Build Directory

Initialize Repo

Step 3: Sync Source Code

Step 4: Add Device Trees

Required Repositories

Using Local Manifests

Step 5: Configure Build

Set Up Environment

Select Device

Build Types

Step 6: Build!

Start Build

Build Time

Output

Making Modifications

Where to Make Changes

Example: Add System Feature

Common Build Errors

"Jack server error"

Out of Memory

Missing Dependencies

Speed Tips

Use SSD

ccache is Essential

Parallel Jobs

Build Server

Cleaning Builds

Clean Output

Deep Clean

Remove ccache

Sharing Your ROM

Create Release

Publish

Documentation

Learning Path

Start Simple

Then Advance

Resources

Summary

🎉 Found this helpful?

Build Custom ROM from Source - Complete Developer Guide

Build Custom ROM from Source

Requirements

Hardware

Software

Step 1: Set Up Build Environment

Install Ubuntu Dependencies

Install Repo Tool

Configure Git

Set Up ccache

Step 2: Initialize Repository

Create Build Directory

Initialize Repo

Step 3: Sync Source Code

Step 4: Add Device Trees

Required Repositories

Using Local Manifests

Step 5: Configure Build

Set Up Environment

Select Device

Build Types

Step 6: Build!

Start Build

Build Time

Output

Making Modifications

Where to Make Changes

Example: Add System Feature

Common Build Errors