Building CUSTOM ROM

Guide on Building Android Custom ROM

Prerequisites:

A Linux distribution such as Ubuntu or Arch
A minimum of 16GB RAM, with an additional 32GB of swap space
At least 400GB of free storage
A 6-core CPU (or higher is recommended)
Device trees for the specific device you will be building

Requirements for Building an Android ROM

To build an Android ROM, you need the following:

Device Tree
Kernel Tree
Vendor Tree

You can find these trees on the LineageOS GitHub repository. Some devices may require additional trees, depending on the model.

Since I am building Evolution X for Google Pixle 7a also known as lynx, I need to modify my device tree to adapt it for this ROM. Here are examples for:

After these modifications, we’re ready to begin building.

Installing Required Packages

For Ubuntu 24.04, use:

sudo apt install git bc bison build-essential ccache curl flex g++-multilib gcc-multilib git git-lfs gnupg gperf imagemagick lib32readline-dev lib32z1-dev libelf-dev liblz4-tool libsdl1.2-dev libssl-dev libxml2 libxml2-utils lzop pngcrush rsync schedtool squashfs-tools xsltproc zip zlib1g-dev

For Arch-based distros, use:

yay -S git aosp-devel

Setting Up the Build Environment

First, create the necessary directories:

mkdir -p ~/bin
mkdir -p ~/evo

Install the Repo command:

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

Configure Git:

git config --global user.email "you@example.com"
git config --global user.name "Your Name"
git lfs install

Enable caching to speed up builds:

export USE_CCACHE=1
export CCACHE_EXEC=/usr/bin/ccache
ccache -M 50G

Set the cache size between 30-50GB for building a single device.

Downloading the ROM Source Code

Since we’re building Evolution X, follow the Evolution X sync instructions.

Navigate to the build directory and initialize the repository:

cd ~/evo
repo init -u https://github.com/Evolution-X/manifest -b udc --git-lfs

Sync the repository:

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

This process may take a few hours, depending on your internet speed.

Preparing Device Trees

For the Pixel 7a (Lynx), here are the trees to clone:

Main Device Tree: device/google/lynx
Additional Trees:
- device/google/gs201
- device/google/gs101
- device/google/gs-common
- Prebuilt Kernel: device/google/lynx-kernel
- Vendor Trees: vendor/google/lynx

For each tree, use:

git clone <repository-url> <target-directory>

Example:

git clone https://github.com/razinares/device_google_lynx -b Evolution-X device/google/lynx

Once all trees are cloned in the correct directories, you can start the build.

Building the ROM

Switch to the build environment:

. build/envsetup.sh

Set the build type with lunch. Evolution X uses the lunch command (some ROMs use brunch):

lunch lineage_lynx-userdebug

Where:

lynx is the device codename
userdebug is the build variant

The three build variants:

user: Suitable for daily usage.
userdebug: Enables logging features.
eng: Faster build time, suitable for development. Not recommended for daily use.

Start building Evolution X:

m evolution

The build process may take a few hours. For example, on my Ryzen 3600, it takes about 3 hours.

After a successful build, navigate to the output directory to retrieve the necessary files:

cd $OUT

For flashing, you’ll need:

vendor_boot.img - Recovery image
EvolutionX-14.0-20241014-lynx-v9.5-Unofficial.zip

If you encounter issues, use adb logcat to review logs, troubleshoot errors, and resolve any issues.

References:

Happy Building!