"多快好省"——交叉编译构建自己的linux操作系统(2)

谁借莪１个温暖的怀抱￠ 2022-02-02 05:27 437阅读 0赞

### 前言 ###

*  这里我们在《“多快好省”——交叉编译构建自己的linux操作系统》的基础上，使用busybox来构建initrd，在基于XFS文件系统的SATA硬盘上构建带有initrd的linux操作系统

### 设置编译环境 ###

set +h
    umask 022
    export LJOS=~/lj-os
    export LC_ALL=POSIX
    export PATH=${LJOS}/cross-tools/bin:/bin:/usr/bin
    unset CFLAGS
    unset CXXFLAGS
    export LJOS_HOST=$(echo ${
         MACHTYPE} | sed "s/-[^-]*/-cross/")
    export LJOS_TARGET=x86_64-unknown-linux-gnu
    export LJOS_CPU=k8
    export LJOS_ARCH=$(echo ${
         LJOS_TARGET} | sed -e 's/-.*//' -e 's/i.86/i386/')
    export LJOS_ENDIAN=little
    export CC="${LJOS_TARGET}-gcc"
    export CXX="${LJOS_TARGET}-g++"
    export CPP="${LJOS_TARGET}-gcc -E"
    export AR="${LJOS_TARGET}-ar"
    export AS="${LJOS_TARGET}-as"
    export LD="${LJOS_TARGET}-ld"
    export RANLIB="${LJOS_TARGET}-ranlib"
    export READELF="${LJOS_TARGET}-readelf"
    export STRIP="${LJOS_TARGET}-strip"

### 静态编译busybox ###

*  这里为了方便我配置busybox为静态编译Busybox(Settings --> Build Options --> Build BusyBox as a static binary (no shared libs)

make CROSS_COMPILE="${LJOS_TARGET}-" menuconfig
    make CROSS_COMPILE="${LJOS_TARGET}-"
    make CROSS_COMPILE="${LJOS_TARGET}-"  install

![1][]

### 以ko的形式编译xfs驱动 ###

*  配置xfs

make ARCH=${LJOS_ARCH} CROSS_COMPILE=${LJOS_TARGET}- menuconfig

![2][]

*  编译驱动

make ARCH=${LJOS_ARCH} CROSS_COMPILE=${LJOS_TARGET}-

### 构建initramfs ###

![3][]

*  skeleton

mkdir initramfs
    cp -R busybox-1.28.3/_install/* initramfs/ 
    cd initramfs
    mkdir dev etc lib mnt proc sys
    cp -R ../busybox-1.28.3/examples/bootfloppy/etc/* etc/

*  修改etc/inittab内容

::sysinit:/etc/init.d/rcS
    ::respawn:-/bin/sh
    tty2::askfirst:-/bin/sh
    ::ctrlaltdel:/bin/umount -a -r

*  修改后为

::sysinit:/etc/init.d/rcS
    console::respawn:-/bin/sh

*  修改etc/fstab，增加自己的挂载操作

proc	/proc	proc	defaults 0	0

*  创建设备文件

mknod dev/console c 5 1
    mknod dev/null c 1 3

*  重新创建init脚本  
    ![4][]

# init的内容
    #!/bin/sh
    #
    echo "exec initramfs init"
    echo "mounting proc and sys"
    
    mount -t proc proc /proc
    mount -t sysfs sysfs /sys
    
    insmod /lib/modules/4.16.3/kernel/lib/libcrc32c.ko
    insmod /lib/modules/4.16.3/kernel/fs/xfs/xfs.ko
    
    echo "detect and export hardware info"
    mdev -s
    
    
    echo "Mount real rootfs to /mnt/sysroot..."
    mkdir /mnt/sysroot
    mount -t xfs /dev/sda2 /mnt/sysroot
    
    echo "Switch to read rootfs..."
    exec switch_root /mnt/sysroot /linuxrc
    #exec switch_root /mnt/sysroot /sbin/init

*  把xfs驱动加入到initrd

mkdir -p lib/modules/4.16.3/kernel/fs/xfs/
    cp /root/ljos_tar/linux-4.16.3/fs/xfs/xfs.ko lib/modules/4.16.3/kernel/fs/xfs/

*  制作initrd

find . |cpio -o -H newc | gzip > ../initrd.img

### 给SATA硬盘分区 ###

*  分两个区，并格式化成xfs文件系统，挂载到编译机上（/root/sda1和/root/sda2）

|/dev/sdb
    |---------/dev/sdb1(用于/boot)
    |---------/dev/sdb2（用于/）

*  安装bootloarder

# 将SATA硬盘的根分区挂载到编译机的/root/sda2，boot分区挂载到编译机的/root/sda2/boot，然后安装grub2
    grub2-install --root-directory=/root/sda2 /dev/sdb

### 配置bootloarder ###

*  这里我直接复用了centos7的grub2的配置

[root@localhost sda2]# cat boot/grub2/grub.cfg 
    #
    # DO NOT EDIT THIS FILE
    #
    # It is automatically generated by grub2-mkconfig using templates
    # from /etc/grub.d and settings from /etc/default/grub
    #
    
    ### BEGIN /etc/grub.d/00_header ###
    set pager=1
    
    if [ -s $prefix/grubenv ]; then
      load_env
    fi
    if [ "${next_entry}" ] ; then
       set default="${next_entry}"
       set next_entry=
       save_env next_entry
       set boot_once=true
    else
       set default="${saved_entry}"
    fi
    
    if [ x"${feature_menuentry_id}" = xy ]; then
      menuentry_id_option="--id"
    else
      menuentry_id_option=""
    fi
    
    export menuentry_id_option
    
    if [ "${prev_saved_entry}" ]; then
      set saved_entry="${prev_saved_entry}"
      save_env saved_entry
      set prev_saved_entry=
      save_env prev_saved_entry
      set boot_once=true
    fi
    
    function savedefault {
        
      if [ -z "${boot_once}" ]; then
        saved_entry="${chosen}"
        save_env saved_entry
      fi
    }
    
    function load_video {
        
      if [ x$feature_all_video_module = xy ]; then
        insmod all_video
      else
        insmod efi_gop
        insmod efi_uga
        insmod ieee1275_fb
        insmod vbe
        insmod vga
        insmod video_bochs
        insmod video_cirrus
      fi
    }
    
    if [ x$feature_timeout_style = xy ] ; then
      set timeout_style=menu
      set timeout=5
    # Fallback normal timeout code in case the timeout_style feature is
    # unavailable.
    else
      set timeout=5
    fi
    ### END /etc/grub.d/00_header ###
    
    ### BEGIN /etc/grub.d/00_tuned ###
    set tuned_params=""
    ### END /etc/grub.d/00_tuned ###
    
    ### BEGIN /etc/grub.d/01_users ###
    if [ -f ${prefix}/user.cfg ]; then
      source ${prefix}/user.cfg
      if [ -n ${GRUB2_PASSWORD} ]; then
        set superusers="root"
        export superusers
        password_pbkdf2 root ${GRUB2_PASSWORD}
      fi
    fi
    ### END /etc/grub.d/01_users ###
    
    ### BEGIN /etc/grub.d/10_linux ###
    menuentry 'OS1.0a'  {
        
            load_video
            set gfxpayload=keep
            insmod gzio
            insmod part_msdos
            insmod xfs
            set root='hd0,msdos1'
            linux /vmlinuz-4.16.3 root=/dev/sda2 ro 
            initrd /initrd.img
    }

*  把制作好的initrd.img放入/root/sda2/boot（即boot分区下）

### 启动目标机硬盘 ###

![5][]

*  正常启动，且加载了xfs驱动  
    ![d][]

[1]: /images/20220202/508941bd82f9487b996219144e9e9e25.png
[2]: /images/20220202/a3a176c618a54e23bc57124bcf830dac.png
[3]: /images/20220202/4284b8d2dd4a4faf984500df48e875f9.png
[4]: /images/20220202/71580e8f7647481c8ed8c54d024685e5.png
[5]: /images/20220202/a8475463f6744c89a7393ccfcb9bd3c4.png
[d]: /images/20220202/0fc6d5796e714a8ea35b2c7e02e0d1b8.png