---
title: Recompile Kernel on Linux
tags: Intern, APM
description: Recompile to fit the hardware
---

# Recompile Kernel on Linux

## Prerequisite of Building the Kernel
- Check gcc is installed
- Tools needed:

sudo apt-get install build-essential libncurses5-dev xz-utils libssl-dev kernel-package wget

## Step1.0 :到 Kernel.org 下載需要的版本
- 用 git clone 或 wget 下載原始碼 並丟到 /usr/src 的資料夾下

wget https://github.com/torvalds/linux/archive/v4.x/linux-4.15.tar.gz 
tar zxvf linux-4.15.tar.gz
cd linux-4.15/

## Step1.1 :Ubuntu Launchpad the Sub-version of Kernel Source Code
Link:https://launchpad.net/ubuntu/+source/linux/4.15.0-50.54
- There are 3 files to be downloaded `linux_4.15.0.orig.tar.gz & linux_4.15.0-50.54.diff.gz & linux_4.15.0-50.54.dsc`
- .orig.tar.gz -> The original kernel
- .diff.gz -> The diffence (patch) between the updated code and the original code.
- .dsc -> A short textfile descripts of the .orig and .diff and connect the files above
- Use the dpkg to extract the files

$ dpkg-source -x package.dsc

## Step2: 設定 config 來調整硬體需求
- 複製原有的 config 檔案，重新存成一份 .config
- 可用xconfig,or menuconfig 來設定config檔
- Change the name of compile kernel version name:
`vim Makefile`
to change the version name as the photo below before compiling

cp /boot/config-4.4.0-21-generic ./.config
make menuconfig

## Step3: Compile the kernel
- -j 4 代表使用4核心進行編譯，可以加速 compile 的慢長過程

sudo make -j 4 clean
sudo make -j 4
sudo make modules -j 4
sudo make modules_install
sudo make install

## Step4: 更新initramfs image

 sudo update-initramfs -u -k all

## Step5: 更新grub-list
- 重開機後按 Esc 開機選單就可看到可選的新裝好的kernel開機

 sudo update-grub 

# 開機後用指定版本Kernel開機
- Edit string in /etc/default/grub, then save

shell > sudo vim /etc/default/grub
/*
edit from
GRUB_DEFAULT=0
save to
GRUB_DEFAULT=saved
*/


- 查看目前開機的kernel modules

shell > awk -F\' '$1=="menuentry " || $1=="submenu " {print i++ " : " $2}; /\tmenuentry / {print "\t" i-1">"j++ " : " $2};' /boot/grub/grub.cfg


- 選擇指定的kernel 版本並下以下指令, 以下是以想要使用"4.4.0-87"('1>4')為例

shell > sudo grub-set-default '1>4'
shell > sudo update-grub
shell > sudo reboot

# Ubuntu package of Kernel (compiled)

sudo apt-get linux-header-4.15.0-55-generic