LINUX磁盘的分区和格式化-岸边IBIAN

经常做的事情就是拿一个全新的磁盘来分区并格式化。这也说明了作为一个linux系统管理员，对于磁盘的操作必须要熟练。所以请你认真学习该部分内容。在正式介绍Linux下分区工具之前，需要先给虚拟机添加一块磁盘，以便于我们做后续的实验，如果你也是使用vmware 虚拟机，请跟着一起来做吧。

先关闭正在运行的Linux系统
```
init 0
```
到vmware的Linux虚拟机界面，点 “Edit virtual machine settings”, 点一下左侧靠下面的 “Add…” 按钮。
在左侧选中 “Hard Disk” 默认就是这一行，点右下角的 “Next”, 继续点 “Next”.
“Virtual disk type” 选择 IDE, 点 “Next”
继续点 “Next”, “Disk size” 默认即可，最后点 “Finish”.

命令 : fdisk
fdisk 是Linux下硬盘的分区工具，是一个非常实用的命令，但是fdisk只能划分小于2T的分区。
语法 : fdisk [-l ] [设备名称] 选项只有一个。
“-l” 后边不跟设备名会直接列出系统中所有的磁盘设备以及分区表，加上设备名会列出该设备的分区表。

[root@localhost ~]# fdisk -l
Disk /dev/sda: 17.2 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 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: 0x00018d63
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      102400   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              13         274     2097152   82  Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3             274        2089    14576640   83  Linux
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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
[root@localhost ~]# fdisk -l /dev/sda
Disk /dev/sda: 17.2 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 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: 0x00018d63
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      102400   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              13         274     2097152   82  Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3             274        2089    14576640   83  Linux

可以看到刚才加的一块磁盘 /dev/sdb 的信息。
“fdisk” 如果不加 “-l” 则进入另一个模式，在该模式下，可以对磁盘进行分区操作。

[root@localhost ~]# fdisk /dev/sda
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').
Command (m for help):

如果你输入 ‘m’ 会列出常用的命令：

Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

如果你的英文好，我想你不难理解这些字母的功能。常用的有’p’, ‘n’, ‘d’, ‘w’, ‘q’.
“p” 打印当前磁盘的分区情况。

Command (m for help): p
Disk /dev/sda: 17.2 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 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: 0x00018d63
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      102400   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              13         274     2097152   82  Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3             274        2089    14576640   83  Linux

‘n’ 建立一个新的分区。
‘w’ 保存操作。
‘q’ 退出。
‘d’ 删除一个分区
下面会把刚才增加的磁盘/dev/sdb进行分区操作。先使用 ‘p’ 命令看一下/dev/sdb的分区状况：

[root@localhost ~]# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0xf4121235.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0xf4121235
   Device Boot      Start         End      Blocks   Id  System
Command (m for help):

可以看到目前/dev/sdb没有任何分区，下面给它建立第一个分区：

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)

使用 ‘n’ 命令新建分区，它会提示是要 ‘e’ (扩展分区) 还是 ‘p’ (主分区) 的选择是 ‘p’, 于是输入 ‘p’ 然后回车

Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-1044, default 1): 1
Last cylinder, +cylinders or +size{K,M,G} (1-1044, default 1044): +1000M

输入 ‘p’ 后，会提示分区数，这里写 ‘1’, 因为是第一个分区，当然你也可以写 ‘2’ 或 ‘3’, 如果你直接回车的话，会继续提示你必须输入一个数字，接着又提示第一个柱面从哪里开始，默认是 ‘1’, 你可以写一个其他的数字，不过这样就浪费了空间，所以还是写 ‘1’ 吧，或者你直接回车也会按 ‘1’ 处理，接着是让输入最后一个柱面的数值，也就是说你需要给这个分区分多大空间，关于柱面是多大不再细究，你只需要掌握教给你的方法即可，即写 “+1000M”, 这样即方便又不容易出错。用 ‘p’ 查看已经多出了一个分区：

Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x0600660a
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         128     1028128+  83  Linux

继续上面的操作，一直创建主分区到4, 然后再一次创建分区的时候则会提示：

Command (m for help): n
You must delete some partition and add an extended partition first

这是因为，在linux中最多只能创建4个主分区，那如果你想多创建几个分区如何做？很容易，在创建完第三个分区后，创建第四个分区时选择扩展分区。

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
e
Selected partition 4
First cylinder (385-1044, default 385):
Using default value 385
Last cylinder, +cylinders or +size{K,M,G} (385-1044, default 1044):
Using default value 1044
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0xef267349
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         128     1028128+  83  Linux
/dev/sdb2             129         256     1028160   83  Linux
/dev/sdb3             257         384     1028160   83  Linux
/dev/sdb4             385        1044     5301450    5  Extended

扩展分区，在最后一列显示为 “Extended”, 接下来继续创建分区：

Command (m for help): n
First cylinder (385-1044, default 385):
Using default value 385
Last cylinder, +cylinders or +size{K,M,G} (385-1044, default 1044): +1000M
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0xef267349
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         128     1028128+  83  Linux
/dev/sdb2             129         256     1028160   83  Linux
/dev/sdb3             257         384     1028160   83  Linux
/dev/sdb4             385        1044     5301450    5  Extended
/dev/sdb5             385         512     1028128+  83  Linux

这时候再分区和以前有区别了，不再选择是主分区还是扩展分区了，而是直接定义大小。有一点要讲一下，当分完三个主分区后，第四个扩展分区需要把剩余的磁盘空间全部划分给扩展分区，不然的话剩余的空间会浪费，因为分完扩展分区后，再划分新的分区时是在已经划分的扩展分区里来分的。其中/dev/sdb4为扩展分区，这个分区是不可以格式化的，你可以把它看成是一个空壳子，能使用的为/dev/sdb5, 其中/dev/sdb5为/dev/sdb4的子分区，这个子分区叫做逻辑分区。如果你发现分区分的不合适，想删除掉某个分区怎么办？这就用到了 ‘d’ 命令：

Command (m for help): d
Partition number (1-5): 1
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2             129         256     1028160   83  Linux
/dev/sdb3             257         384     1028160   83  Linux
/dev/sdb4             385        1044     5301450    5  Extended
/dev/sdb5             385         512     1028128+  83  Linux
Command (m for help): d
Partition number (1-5): 5
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2             129         256     1028160   83  Linux
/dev/sdb3             257         384     1028160   83  Linux
/dev/sdb4             385        1044     5301450    5  Extended
Command (m for help): n
Command action
   l   logical (5 or over)
   p   primary partition (1-4)
l
First cylinder (385-1044, default 385):
Using default value 385
Last cylinder, +cylinders or +size{K,M,G} (385-1044, default 1044): +1000M
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2             129         256     1028160   83  Linux
/dev/sdb3             257         384     1028160   83  Linux
/dev/sdb4             385        1044     5301450    5  Extended
/dev/sdb5             385         512     1028128+  83  Linux
Command (m for help): d
Partition number (1-5): 4
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2             129         256     1028160   83  Linux
/dev/sdb3             257         384     1028160   83  Linux

输入 ‘d’ 会提示要删除哪个分区，可以选择从 1-5 其中1-3是主分区(sdb1, sdb2, sdb3)，4是扩展分区(sdb4)，5是逻辑分区 [1] (sdb5)，如果输入5，则直接把逻辑分区sdb5删除掉，但是如果输入4的话，会把整个扩展分区sdb4干掉，当然也包含扩展分区里面的逻辑分区sdb5。在刚才的分区界面直接 Ctrl + C 退出来，这样刚刚的分区全部都取消了，咱们重新来做分区：

[root@localhost ~]# fdisk /dev/sdb
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
e
Partition number (1-4): 1
First cylinder (1-1044, default 1): 1
Last cylinder, +cylinders or +size{K,M,G} (1-1044, default 1044): 1044
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        1044     8385898+   5  Extended
Command (m for help): n
Command action
   l   logical (5 or over)
   p   primary partition (1-4)

如果把第一个分区分为扩展分区，并且把全部空间都分给扩展分区的话，再继续分区的话，会提示的分区类型为主分区还是逻辑分区(logical), 用 ‘l’ 表示逻辑分区，逻辑分区的id是从5开始的，因为前四个id为主分区或者扩展分区。既然把所有磁盘空间都分为了扩展分区，如果你在这里选择 ‘p’ 则会报错：

Command action
   l   logical (5 or over)
   p   primary partition (1-4)
p
Partition number (1-4): 2
No free sectors available

这是因为没有足够空间分给主分区了，那我们就分逻辑分区：

Command (m for help): n
Command action
   l   logical (5 or over)
   p   primary partition (1-4)
l
First cylinder (1-1044, default 1): 1
Last cylinder, +cylinders or +size{K,M,G} (1-1044, default 1044): +1000M
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        1044     8385898+   5  Extended
/dev/sdb5               1         128     1028097   83  Linux
Command (m for help): n
Command action
   l   logical (5 or over)
   p   primary partition (1-4)
l
First cylinder (129-1044, default 129): 129
Last cylinder, +cylinders or +size{K,M,G} (129-1044, default 1044): +1000M
Command (m for help): p
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        1044     8385898+   5  Extended
/dev/sdb5               1         128     1028097   83  Linux
/dev/sdb6             129         256     1028128+  83  Linux

分区完后，需要输入 ‘w’ 命令来保存我们的配置：

Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.

再使用 fdisk -l /dev/sdb 查看分区情况：

[root@localhost ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 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: 0x7b9a6af3
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        1044     8385898+   5  Extended
/dev/sdb5               1         128     1028097   83  Linux
/dev/sdb6             129         256     1028128+  83  Linux

通过以上操作，相信你也学会了用fdisk来分区了吧。不要闲着没事分区玩儿，这操作的危险性是很高的，一不留神就把服务器上的数据全部给分没有了。所以在你执行分区操作的时候，请保持百分之二百的细心，切记切记！

THE END