Linux内核编程学习笔记-001-编译和启动内核

Linux内核编程学习笔记-001-编译和启动内核

Linux内核学习笔记-001-编译和启动内核

本文来源：Moeomu的博客

准备环境

Ubuntu 20.04 LTS
Linux 4.9.229
Busybox 1.33.0
qemu

下载内核源代码和文件系统源代码

在站点Kernel.org下载linux-4.9.229.tar.gz
在站点Busybox.net下载busybox-1.33.0.tar.bz2
通过apt安装qemu：sudo apt install qemu-system-x86

编译

编译内核

export ARCH=x86
make x86_64_defconfig
make menuconfig
- 选中General Setup -> Initial RAM filesystem and RAM disk(initramfs/initrd) support
- 选中Device Drivers -> Block devices -> RAM block device support
- 修改Device Drivers -> Block devices -> RAM block device support -> (65536)default RAM disk size (kbytes)

如果这一步报错fatal error: curses.h，则安装一下sudo apt install libncurses5-dev

make
编译好的内核被放置在目录arch/x86/boot下，文件名bzImage

编译busybox

make menuconfig
- 选中Settings -> Build Options -> [*] Build Busybox as a static binary (no shard libs)
make && make install

打包文件系统

mkdir etc dev mnt
mkdir -p proc sys tmp
mkdir -p etc/init.d

vim etc/fstab

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proc /proc proc defaults 0 0
tmpfs /tmp tmpfs defaults 0 0
sysfs /sys sysfs defaults 0 0

vim etc/init.d/rcS

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echo -e "Welcome to Moeomu Linux"
/bin/mount -a
echo -e "Remounting the root filesystem"
mount -o remount rw /
mkdir -p /dev/pts
moutn -t devpts devpts /dev/pts
echo /sbin/mdev > /proc/sys/kernel/hotplug
mdev -s

chmod 755 etc/init.d/rcS

vim etc/inittab

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::sysinit:/etc/init.d/rcS
::respawn:-/bin/sh
::askfirst:-/bin/sh
::cttlaltdel:/bin/umount -a -r

chmod 755 etc/inittab
cd dev
sudo mknod console c 5 1
sudo mknod null c 1 3
sudo mknod tty1 c 4 1

以下代码在busybox源码目录下逐行执行

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#!/bin/bash
rm -rf rootfs.ext3
sudo rm -rf fs
dd if=/dev/zero of=./rootfs.ext3 bs=1M count=32
mkfs.ext3 rootfs.ext3
mkdir fs
sudo mount -o loop rootfs.ext3 ./fs
sudo cp -rf ./_install/* ./fs
sudo umount ./fs
gzip --best -c rootfs.ext3 > rootfs.img.gz

最终生成了文件系统：rootfs.img.gz

使用QEMU运行系统

qemu-system-x86_64 -kernel ./linux-4.9.229/arch/x86_64/boot/bzImage -initrd ./busybox-1.33.1/rootfs.img.gz -append "root=/dev/ram init=/linuxrc" -serial file:output.txt
预览如下