A guide of How to Build Linux Kernel using android

Building Linux Kernel With Android.md

How to Build Linux Kernel with Android

This guide shows how to build Linux on a Android Device and was made for people that doesn't have s Computer.

Minimum Requiriments:

• 4GB of free space (2GB if delete the temp files)
• Android 5.0

Preparing the Environment

You need to install Termux from Google Play Store. Now we will download the Kernel so we need WGET:

apt-get update &&
apt-get --assume-yes install wget &&
cd ~ &&
wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.4.6.tar.xz

The next step is decompress that tarball with UNXZ and TAR (integrated with Termux):

unzx -d linux-5.4.6.tar.xz  &&
tar -xf linux-5.4.6.tar

(Optional) Delete the Linux tarball:

rm linux-5.4.6.tar

Now we have the Linux Source on our Android, lets compile!

Compiling

In Android, compile is a terror for Linux Kernel. First we need to create a config file.

The .config file dilemma

If you had an Linux PC you could simply do this:

cp /boot/config-$(uname -r) linux-5.4.6/.config

But you dont have, so we need to do this:

Root mode (easy)

If you have a Rooted Potato Phone you can simply:

cp /proc/config.gz ~ &&
gzip -d config.gz &&
mv config linux-5.4.6/.config &&
cd linux-5.46

No Root mode (medium)

If else, first you need to download it from our repository:

wget https://eduapps-cdg.github.io/kernel-configs/raw/master/android/$(getprop | grep -i ro.product.model | sed "s/\[ro.product.model\]: //" | sed "s/\[//" | sed "s/\]//").gz &&
mv $(getprop | grep -i ro.product.model | sed "s/\[ro.product.model\]: //" | sed "s/\[//" | sed "s/\]//").gz config.gz &&
gzip -d config.gz &&
mv config linux-5.4.6/.config &&
cd linux-5.46

No Root mode (hard)

If the file was not found, you must generate it. It has only one command, but this command is the worst! It's the best choice if you are developing a new device. Complete the first command of Building and type:

make menuconfig

Building

Once solved the dilemma, you will not need to do it again. the next step is install the compilers:

apt-get install build-essential ncurses bison flex openssl libelf clang

This command will setup to build the Kernel with full power, if you have a single core device, it doesn't help so much but works:

make -j $(nproc)
make modules_install
make install

And finally, the Last Step is: Enjoy the building time and drink a coffee!

Can it be used to natively compile the same kernel that is running on the phone?

This is quite outdated - I'm trying to compile the newest kernel (6.11) and I have the same issue (bcmp not found), even adding the flag -fno-builtin-bcmp does not work...
It does not work either with the provided kernel version either.