Kernel Config

https://community.cloud.online.net/t/official-linux-kernel-new-modules-optimizations-hacks/226

The kernel is built with the official mainline kernel, here are the .config files used.

Modifications

We added kernel module to simulate some virtualization features:

• serial console activation
• remote soft reset trigger

---

How to build a custom kernel module

# Get kernel sources
KERNEL_RELEASE_VERSION=4.2  # warning: usually equal to $(uname -r) but not everytime
mkdir -p -- /usr/src
cd /usr/src
wget https://kernel.org/pub/linux/kernel/v4.x/linux-${KERNEL_RELEASE_VERSION}.tar.xz
tar xf linux-${KERNEL_RELEASE_VERSION}.tar.xz
ln -s linux-${KERNEL_RELEASE_VERSION} linux
ln -s /usr/src/linux /lib/modules/$(uname -r)/build

# Prepare kernel
cd /usr/src/linux
zcat /proc/config.gz > .config
wget http://mirror.scaleway.com/kernel/$(uname -r)/Module.symvers
make prepare module_prepare

Then you can make your module as usual by configuring KDIR=/lib/modules/$(uname -r)/build/

Kernels

Name	Maintainer	Sources	Target	Links
3.2.34	Marvell	Closed	C1	n/a
3.18.20	Linux community	Open	C1	Sources
3.19.8	Linux community	Open	C1	Sources
4.1.6	Linux community	Open	C1	Sources
4.2	Linux community	Open	C1	Sources

---

Build a custom kernel using Docker

Run a make menuconfig for 3-18-std/.config

make menuconfig KERNEL=3.18-std

Build a kernel with 3.17-std/.config file

make build KERNEL=3.17-std

Advanced options

Create a new 3.10-new/.config file from scratch for kernel 3.10

make create defconfig KERNEL=3.10-new

Make oldconfig a 3.18-std kernel

make oldconfig KERNEL=3.18-std

Run a shell in the container for easy debugging and run custom commands

make shell KERNEL=3.17-std

Test a kernel with QEMU

You should use a config file made for versatile.

Build a 3.18 kernel for versatile:

make build KERNEL=3.18-defconfig_versatile

Run the kernel in qemu

make qemu KERNEL=3.18-defconfig_versatile

How to upgrade a kernel

An example with 4.0.8-docker

You should move the directory

git mv 4.0.8-docker 4.0.9-docker

Run a make oldconfig with the newest version

make oldconfig KERNEL=4.0.9-docker

---

Build a custom kernel from scratch (without Docker)

Prerequisites:

• An arm(hf) compiler:
  • a cross-compiler on non-armhf host, ie gcc-arm-linux-gnueabihf
  • a standard compiler from an armhf host (you can build a kernel from your C1)
• Theses packages: git, wget, make

Steps:

• Configure environment

export VERSION=3.17 export ARCH=arm export ARTIFACTS=artifacts

- Download archive via web
  ```bash
wget https://kernel.org/pub/linux/kernel/v3.x/linux-$VERSION.tar.xz && tar xf linux-$VERSION.tar.xz

or via git

git clone -b v$VERSION --single-branch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-$VERSION

• Generate a base .config file by building it

make ARCH=arm mvebu_v7_defconfig

  or by fetching our one

wget -O .config https://raw.githubusercontent.com/scaleway/kernel-tools/master/$VERSION/.config

- Tune the .config
  ```bash
make ARCH=arm menuconfig
# ... configure using console interface

• Building kernel and modules

make -j $(echo nproc ' * 2' | bc) uImage modules LOADADDR=0x8000

- Export the artifacts (kernel, header, modules) to `$ARTIFACTS` directory
  ```bash
mkdir -p $ARTIFACTS
cp arch/arm/boot/uImage $ARTIFACTS/
cp System.map $ARTIFACTS/
cp .config $ARTIFACTS/
make headers_install INSTALL_HDR_PATH=$ARTIFACTS/ > /dev/null
find $ARTIFACTS/include -name ".install" -or -name "..install.cmd" -delete
make modules_install INSTALL_MOD_PATH=$ARTIFACTS/ > /dev/null
rm -rf $ARTIFACTS/modules && \
   mv $ARTIFACTS/lib/modules $ARTIFACTS && \
   rmdir $ARTIFACTS/lib && \
   rm $ARTIFACTS/modules/*/source $ARTIFACTS/modules/*/build

Minimal configuration for C1 servers

- Networking support
  - Networking options
    - 802.1Q/802.1ad VLAN Support -> **YES**
    - Packet socket -> **YES**
    - Unix domain sockets -> **YES**
- Device Drivers
  - Network device support
    - PHY Device support and infrastructure
      - Driver for MDIO Bus/PHY emulation with fixed speed/link PHYs -> **YES**
  - Block devices
    - Network block device support -> **YES**
- Kernel hacking
  - Kernel low-level debugging functions -> **YES**
  - Early prink -> **YES**
- File systems
  - The Extended 4 (ext4) filesystem -> **YES**

Licensing

© 2014-2015 Scaleway - MIT License.