linux2.4.18----25.文件系统的构建

一. 文件系统的构建
1.busybox的编译
方法: 用虚拟机的redhat9.0进行编译
版本: busybox-1.00  -->make menuconfig -->make -->make install 

cong@msi:/work/os/rootfs/busybox/busybox-1.00$ readelf -a ./busybox | grep "NEEDED"
 0x00000001 (NEEDED) Shared library: [libm.so.6]       -->所以文件系统中需要包含这两个库libm与libcrypt，是可选的
 0x00000001 (NEEDED) Shared library: [libcrypt.so.1]
 0x00000001 (NEEDED) Shared library: [libc.so.6]       -->libc库是最基础的任何程库就需要，是必需的

不需要选择  []Build BusyBox as a static binary (no shared libs)   

2. 内核的修改

init/main.c中L128
//int root_mountflags = MS_RDONLY;
int root_mountflags = 0

去掉根文件系统的只读属性，
其中这个root_mountflags会在mount_root-->read_super中设置/dev/hda1的属性为MS_RDONLY

3.etc目录下的文件

cong@msi:/work/os/rootfs/ext2/etc$ tree
.
├── fstab      -->只需要fstab与rcS
├── init.d
│   └── rcS    -->只需要rcS与rcS
└── mtab       -->这个文件是mount程序创建的本身不要文件系统中

fstab的内容:挂载proc

cong@msi:/work/os/rootfs/ext2/etc$ cat fstab
proc /proc  proc      defaults    0         0

rcS的内容，mount all

cong@msi:/work/os/rootfs/ext2/etc$ cat init.d/rcS
#!/bin/sh
mount -a

4. 制作根文件系统的脚本
cong@msi:/work/os/rootfs/ext2$ cat creatext2.sh 

#!/bin/sh
TOPDIR=`pwd`
create_fs()
{
    echo "cong: next create fs"
    #create filesystem
    cd /tmp/ext2

    #先创建系统目录
    sudo mkdir -pv dev/ tmp/ sys/ proc/
    sudo mknod ./dev/tty1 c 4 1
    sudo mknod ./dev/console c 5 1
    #sudo cp $TOPDIR/busybox ./bin/
    #sudo cp $TOPDIR/src/hello ./bin/sh
    sudo cp -arf $TOPDIR/lib ./
    sudo cp -arf $TOPDIR/bin ./
    sudo cp -arf $TOPDIR/sbin ./
    sudo cp -arf $TOPDIR/etc ./
}
mount_fs()
{
    echo "cong: next losetup /dev/loop0"
    sudo losetup /dev/loop0 ./hdc.img
    #512*2048=1048576
    echo "cong: next losetup /dev/loop1"
    sudo losetup -o 1048576 /dev/loop1 /dev/loop0
    echo "cong: next show losetup all"
    sudo losetup -a

    echo "cong: next mount "
    mkdir /tmp/ext2
    sudo mount -t ext2 /dev/loop1 /tmp/ext2/
}
#fdisk hdc.img to ext2 83
make_fs()
{
    #64M
    dd if=/dev/zero of=./hdc.img bs=1M count=64
    fdisk ./hdc.img <<EOF
    n
    p
    1
    2048
    131071
    t
    83
    w
EOF
    sleep 1
    fdisk -l ./hdc.img

    echo "cong: next losetup /dev/loop0"
    sudo losetup /dev/loop0 ./hdc.img
    #512*2048=1048576
    echo "cong: next losetup /dev/loop1"
    sudo losetup -o 1048576 /dev/loop1 /dev/loop0
    echo "cong: next show losetup all"
    sudo losetup -a

    echo "cong: next mkfs ext2 /dev/loop1"
    sudo mkfs.ext2 /dev/loop1

    echo "cong: next mount "
    mkdir /tmp/ext2
    sudo mount -t ext2 /dev/loop1 /tmp/ext2/
    create_fs
}
umount_fs()
{
    sudo umount /tmp/ext2
    sudo losetup -d /dev/loop0
    sudo losetup -d /dev/loop1
    sudo losetup -a
}

clean_fs()
{
    echo "cong: next umount /tmp/ext2"
    sudo umount /tmp/ext2
    echo "cong: next rm -rf /tmp/ext2"
    sudo rm -rf /tmp/ext2
    echo "cong: next losetup -d"
    sudo losetup -d /dev/loop0
    sudo losetup -d /dev/loop1
    echo "cong: next show losetup"
    sudo losetup -a
    echo "cong: next rm -rf ./hdc.img"
    rm -rf ./hdc.img
}

case "$1" in
    fs)
        make_fs
        ;;
    clean)
        clean_fs
        ;;
    mount)
        mount_fs
        ;;
    umount)
        umount_fs
        ;;
    *)
        make_fs
        ;;
esac

5.用到的

cong@msi:/work/os/rootfs/ext2$ tree
.
├── bin                          -->会复制为根文件系统的bin目录
│   ├── busybox
│   ├── busybox_0.60.5
│   ├── cat -> busybox
│   ├── cp -> busybox
│   ├── df -> busybox
│   ├── dmesg -> busybox
│   ├── echo -> busybox
│   ├── grep -> busybox
│   ├── hostname -> busybox
│   ├── ln -> busybox
│   ├── ls -> busybox
│   ├── mkdir -> busybox
│   ├── mknod -> busybox
│   ├── mount -> busybox
│   ├── mv -> busybox
│   ├── netstat -> busybox
│   ├── ping -> busybox
│   ├── ps -> busybox
│   ├── pwd -> busybox
│   ├── rm -> busybox
│   ├── sh -> busybox
│   ├── sync -> busybox
│   ├── touch -> busybox
│   ├── umount -> busybox
│   └── vi -> busybox
├── creatext2.sh               -->制作根文件系统的脚本
├── etc                        -->会复制为根文件系统的etc目录
│   ├── fstab
│   ├── init.d
│   │   └── rcS
│   └── mtab
├── lib                        -->会复制为根文件系统的lib目录
│   ├── ld-linux.so.2          //解释器
│   ├── libc-2.3.2.so          //libc库，这是最基础的
│   ├── libcrypt-2.3.2.so      //剩下的libcrypt与libm库单跑helloworld是不需要的
│   ├── libcrypt.so.1 -> libcrypt-2.3.2.so
│   ├── libc.so.6 -> libc-2.3.2.so //但这儿的busybox用到了，就添加上了
│   ├── libm-2.3.2.so
│   └── libm.so.6 -> libm-2.3.2.so
├── Makefile
├── sbin                      -->会复制为根文件系统的sbin目录
│   ├── ifconfig -> ../bin/busybox
│   ├── init -> ../bin/busybox
│   ├── insmod -> ../bin/busybox
│   ├── lsmod -> ../bin/busybox
│   ├── modprobe -> ../bin/busybox
│   └── rmmod -> ../bin/busybox
└── src                      -->一些测试程序的代码
    ├── as
    │   ├── hello.s
    │   └── Makefile
    ├── hello.c
    ├── Makefile
    ├── mycompile.sh
    └── nasm
        ├── hello
        ├── hello.o
        ├── hello.s
        ├── hello.s_nasm
        ├── init.c_hello
        └── Makefile

8 directories, 54 files

5.1 所用到的文件打包
ext2.rar(下载后改名为ext2.tar.gz)

二.linux-2.6.24可用的文件系统

如果出现如下:

version glibc_2.7 not found -->说明需要更新libc的版本

cong@msi:/work/os/rootfs/ext3$ mv libc-2.3.2.so libc-2.3.2.so_bak
cong@msi:/work/os/rootfs/ext3$ rm libc.so.6
cong@msi:/work/os/rootfs/ext3$ ln -s libc-2.9.so libc.so.6

如果出现如下:

/sbin/init: relocation error: /lib/libc.so.6: symbol _rtld_global_ro, version
GLIBC_PRIVATE not defined in file ld-linux.so.2 with link time reference  -->说明需要更新ld的版本

cong@msi:/work/os/rootfs/ext3/lib$ rm ld-linux.so.2
cong@msi:/work/os/rootfs/ext3/lib$ mv /tmp/ld-2.9.so .
cong@msi:/work/os/rootfs/ext3/lib$ ln -s ld-2.9.so ld-linux.so.2