Turning an Old Android Phone into a Server (Redmi 4X [santoni])
Based on https://github.com/dreemurrs-embedded/arch-linux-santoni
Create img file
dd if=/dev/zero of=rootfs.img bs=1M count=2560
Format img file as ext4 filesystem
mkfs.ext4 rootfs.img
Mount img file
sudo mount rootfs.img /mnt/rootfs
Download Arch Linux ARM64 rootfs
wget http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz
Extract rootfs
sudo bsdtar -xpf ArchLinuxARM-aarch64-latest.tar.gz -C /mnt/rootfs
Install qemu-user-static
sudo pacman -S qemu-user-static
Setup DNS
sudo mv /mnt/rootfs/etc/resolv.conf /mnt/rootfs/etc/resolv.conf.ori
echo "nameserver 8.8.8.8" | sudo tee /mnt/rootfs/etc/resolv.conf
Copy qemu-user-static binary to the rootfs
sudo cp `which qemu-aarch64-static` /mnt/rootfs/sbin/
Mount dev, proc, and sys
sudo mount -o bind /dev /mnt/rootfs/dev
sudo mount -t proc proc /mnt/rootfs/proc
sudo mount -t sysfs sysfs /mnt/rootfs/sys
sudo mount -t devpts devpts /mnt/rootfs/dev/pts
Chroot to the rootfs
...
Build Linux Kernel for Android Device
Download the Kernel Source Code
For example, kernel for Xiaomi Mi8937
git clone https://github.com/LineageOS/android_kernel_xiaomi_msm8937.git --depth=1
Install Cross Compiler
Arch Linux
sudo pacman -S aarch64-linux-gnu-gcc
Ubuntu
sudo apt install gcc-aarch64-linux-gnu
Compile the Kernel
Export the environment variable
export CROSS_COMPILE=aarch64-linux-gnu-
export ARCH=arm64
Create the output folder
mkdir out
Locate the kernel defconfig for the device in arch/arm64/configs, run
make O=out <defconfig>
Example for my device
make O=out vendor/msm8937-perf_defconfig
Or we can copy the defconfig file from outside kernel source code and put in the out directory
...
Lorem ipsum dolor sit amet consectetur adipisicing elit
Nam ut rutrum ex, venenatis sollicitudin urna. Aliquam erat volutpat. Integer eu ipsum sem. Ut bibendum lacus vestibulum maximus suscipit. Quisque vitae nibh iaculis neque blandit euismod.
Lorem ipsum dolor sit amet consectetur adipisicing elit. Nemo vel ad consectetur ut aperiam. Itaque eligendi natus aperiam? Excepturi repellendus consequatur quibusdam optio expedita praesentium est adipisci dolorem ut eius!
Creative Design
Nam ut rutrum ex, venenatis sollicitudin urna. Aliquam erat volutpat. Integer eu ipsum sem. Ut bibendum lacus vestibulum maximus suscipit. Quisque vitae nibh iaculis neque blandit euismod.
...