8.2设备文件及磁盘分区

概览：
设备文件的建立 
        权限    设备名 类型  主设备号 次设备号    
mknod [-m MODE] NAME type [MAJOR MINOR] 建立时，先查看是否存在设备号的冲突
零磁道零扇区是MBR：Master Boot Record
            主引导记录
            512Bytes: 引导启动OS
                前446bytes: 存放程序，bootloader
                64bytes: 分区表，每16bytes标记一个分区，一共4个分区（主分区）
                2bytes: 55AA, MBR有效性标记   标记当前mbr是否有效
fdisk是不支持GPT格式的硬盘分区，parted是能够支持的               
parted [options] [device [command [options...]...]]  直接跟设备不跟其余会分区
-l, --list  会列出全部分区信息
    lists partition layout on all block devices
command   
mklabel label-type
     Create a new disklabel (partition table) of label-type.  label-type should  be  one  of
     "bsd", "dvh", "gpt", "loop", "mac", "msdos", "pc98", or "sun".

mkpart part-type [fs-type] start end
     Make  a  part-type partition with filesystem fs-type (if specified), beginning at start
     and ending at end (by default in megabytes).  fs-type can be one of  "fat16",  "fat32",
     "ext2",  "HFS", "linux-swap", "NTFS", "reiserfs", or "ufs".  part-type should be one of
     "primary", "logical", or "extended".
move partition start end
     Move  partition  so  that it begins at start and ends at end.  Note: move never changes
     the minor number.
rm partition
     Delete partition.
print  Display the partition table.    
# parted /dev/sdb mkpart primary ext4 1 10G    
#parted /dev/sdb rm 1
# parted /dev/sdb print                         
磁盘管理：

    I/O设备：
        磁盘
        网卡

    文件：read, write, open, close

    设备文件：特殊文件
        只有inode，而没有数据

        关联至一个驱动程序，进而跟对应的硬件设备打交道；

        /dev: b, c

            每一个设备都有其设备号：
                主设备号：用于标记设备类型
                次设备号：用于标记同一类型中的不一样设备

     mknod - make block or character special files
     -m, --mode=MODE
              set file permission bits to MODE, not a=rw - umask
        mknod [OPTION]... NAME TYPE [MAJOR MINOR]  主设备号能够相同，次设备号不能相同
        TYPE may be:

       b      create a block (buffered) special file 有缓存

       c, u   create a character (unbuffered) special file 无缓存的

       p      create a FIFO
            设备文件的命名：由ICANN：互联网名称与数字地址分配机构（Internet
             Corporation for Assigned Names and Numbers）
[root@linux_basic tmp]#mknod -m 664 blocktest b 1 20
[root@linux_basic tmp]#ls -l
total 0
brw-rw-r--. 1 root root 1, 20 Jan  4 07:38 blocktest
[root@linux_basic tmp]#rm blocktest
rm: remove block special file `blocktest'? y
[root@localhost tmp]# mknod test c 1 30
[root@localhost tmp]# ls -l
total 0
lrwxrwxrwx. 1 root root     8 Dec  2 13:10 file1 -> softfile
-rw-r--r--. 1 root root     0 Dec  2 13:09 softfile
crw-r--r--. 1 root root 1, 30 Dec  2 13:27 test

    磁盘设备文件命名：
        /dev/hd:
            IDE: 并口接口, 133MB/s
        /dev/sd:
            USB: 串行
            SATA: 串行接口，6Gbps/8
            SCSI: 并行，(Small Computer System Interface) 小型计算机系统接口
            SAS：串行，

            rpm：转数

        /dev/sd[a-z]
            分区：数字
                /dev/sda1
                /dev/sda2

                分区编号：
                    主+扩展分区：1-4
                    逻辑分区：5开始

    硬盘分区：
        磁道：track
            扇区：sector

        柱面：cylinder：
            分区根据柱面划分，在同一盘片上的两面磁头同时读取，速度快

        零磁道零扇区是MBR：Master Boot Record
            主引导记录
            512Bytes: 引导启动OS
                前446bytes: 存放程序，bootloader
                64bytes: 分区表，每16bytes标记一个分区，一共4个分区（主分区）
                2bytes: 55AA, MBR有效性标记   标记当前mbr是否有效

            1T: 3主+1扩展（切割1个或多个逻辑分区）
           
        [root@linux_basic tmp]#fdisk -l | grep -A 3 "^Disk /dev/.*"
        Disk /dev/sda: 48.3 GB, 48318382080 bytes
        255 heads（磁头数）, 63 sectors/track每磁道多少扇区, 5874 cylinders（柱面）
        Units = cylinders of 16065 * 512 = 8225280 bytes
        Sector size (logical/physical): 512 bytes / 512 bytes
        --
        Disk /dev/mapper/vg_lvm-lv1: 12.9 GB, 12884901888 bytes
        255 heads, 63 sectors/track, 1566 cylinders
        Units = cylinders of 16065 * 512 = 8225280 bytes
        Sector size (logical/physical): 512 bytes / 512 bytes
        --
        Disk /dev/mapper/vg_lvm-lv2: 10.7 GB, 10737418240 bytes
        255 heads, 63 sectors/track, 1305 cylinders
        Units = cylinders of 16065 * 512 = 8225280 bytes
        Sector size (logical/physical): 512 bytes / 512 bytes   

        /proc:
        [root@linux_basic tmp]#cat /proc/partitions
        major minor  #blocks  name
       
           8        0   47185920 sda
           8        1     204800 sda1
           8        2   10485760 sda2
           8        3   36494336 sda3
         253        0   12582912 dm-0
         253        1   10485760 dm-1

    分区建立：
     fdisk - Partition table manipulator for Linux
     操做Linux分区表
        查看：fdisk -l [DEVICE]...
   fdisk工具最多能够识别15个分区
        建立分区：fdisk [DEVICE]
            交互式界面，有许多子命令
                p: 显示磁盘分区表
                 p   print the partition table
                n: new，新建分区
                 n   add a new partition
                d: delete，删除分区
                d   delete a partition
                t: 修改分区的系统ID
                t   change a partition's system id
                l: 列表出全部已知的系统ID
                l   list known partition types
                   83  Linux
                   82  Linux swap / So
                   8e  Linux LVM 
                   fd  Linux raid auto
                w: 保存并退出
                w   write table to disk and exit
                q: 不保存退出
                q   quit without saving changes
选n后出现               
     e   extended
   p   primary partition (1-4)

            对于已经有分区处于使用状态的磁盘来说，新建分区后须要让内核重读其分区表：
                CentOS 5:
                    # partprobe [DEVICE]
                CentOS 6:
                    partx -a [DEVICE]
                    partx - telling the kernel about presence and numbering of on-disk partitions.
                    -a     add specified partitions or read disk and add all partitions
                    读磁盘新增的分区
                    kpartx -af  [DEVICE]
                    kpartx - Create device maps from partition tables
                    -a     Add partition mappings
                    -l     List partition mappings that would be added -a
                    -f     force creation of mappings; overrides ’no_partitions’ feature
      查看/proc/partitions,有显示则建立成功
            分区建立工具：sfdisk和parted
------------------------------------------------------------------
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
e
Partition number (1-4): 1
First cylinder (1-6527, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-6527, default 6527): +5G
                            注意这里设定大小时的格式
Command (m for help): p

Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         654     5253223+   5  Extended

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@lvm ~]# partx -a /dev/sdb
  Warning: Disk has a valid GPT signature but invalid PMBR.
  Assuming this disk is *not* a GPT disk anymore.
  Use gpt kernel option to override.  Use GNU Parted to correct disk.
BLKPG: Device or resource busy
error adding partition 1
[root@lvm ~]# kpartx -af /dev/sdb
  Warning: Disk has a valid GPT signature but invalid PMBR.
  Assuming this disk is *not* a GPT disk anymore.
  Use gpt kernel option to override.  Use GNU Parted to correct disk.
[root@lvm ~]# cat /proc/partitions
major minor  #blocks  name

   8        0   52428800 sda
   8        1     204800 sda1
   8        2   10485760 sda2
   8       16   52428800 sdb
   8       17          1 sdb1  说明建立成功了
-------------------------------------------------------------------------------  
死循环的一个简单脚本
[root@lvm ~]# bash -n hello.sh
[root@lvm ~]# ./hello.sh
Hello:ld
Again  hello:jhfld
Again  hello:n
[root@lvm ~]# cat hello.sh
#!/bin/bash
#
read -p "Hello:" kir
while true;do
if [ "$kir" == 'n' ];then
    break;
else
    read -p "Again  hello:" kir
fi
done
------------------------------------------------------------------
    练习：写一个脚本
        一、提示输入一个对其执行分区的新硬件设备文件；
        二、提醒用户接下来的操做销毁全部的数据，你继续吗？
            y或yes: 继续
            n或no：退出
            其它字符：提醒输错了，再来一次；
        三、对磁盘新建分区：
            主分区1：大小512M，
            主分区2：大小2G
        四、建立完成后显示建立的结果；
成功完成及修改次数
----------------------------------------------------------------

[root@lvm shells]# cat disk_part.sh
#!/bin/bash
#
read -p "Input a partition disk device path:" disk
read -p "The following operation will damage the all data on the disk.yes|no(y|n)?" flag

while true;do
 
  if [ "$flag" == 'n' -o "$flag" == 'no' ];then
     break;
  elif [ "$flag" == 'y' -o "$flag" == 'yes' ];then
echo "n
p
1

+512M
n
p
2

+2G w"|fdisk $disk > /dev/null   partx -a $disk   kpartx -af $disk   fdisk -l | grep  "$disk"   read -p "The following operation will damage the all data on the disk.yes|no(y|s)?" flag   else      echo "Input error."      read -p "Again input:" flag    fi done