在创建虚拟机的时候明明分配了50GB的硬盘空间！但是在使用df -h命令查看的时候
[root@centos-fuwenchao ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 9.7G 4.6G 4.6G 51% / tmpfs 495M 37M 459M 8% /dev/shm
还以为是自己创建的时候数字写错了，发现有个fdisk命令
[root@centos-fuwenchao ~]# fdisk -l Disk /dev/sda: 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: 0x0004b51e Device Boot Start End Blocks Id System /dev/sda1 * 1 1275 10240000 83 Linux /dev/sda2 1275 1536 2095104 82 Linux swap / Solaris /dev/sda3 1536 6528 40092672 83 Linux
原来是系统启动的时候没有把磁盘挂载上去
现学习下fdisk的具体用法：
一、在 console 上输入 fdisk -l /dev/sda ，观察硬盘之实体使用情形。
[root@centos-fuwenchao ~]# fdisk -l /dev/sda Disk /dev/sda: 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: 0x0004b51e #分区序列 引导 开始 终止 容量 分区类型ID 分区类型 Device Boot Start End Blocks Id System /dev/sda1 * 1 1275 10240000 83 Linux /dev/sda2 1275 1536 2095104 82 Linux swap / Solaris /dev/sda3 1536 6528 40092672 83 Linux
关于fdisk -l 一些数值的说明
Disk /dev/hda: 53.7 GB, 80026361856 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
这个硬盘是53.7G的，有255个磁面；63个扇区；6527个磁柱；每个 cylinder（磁柱）的容量是 8225280 bytes=8225.280 K（约为）=8.225280M（约为）；
硬盘分区的表示：在Linux 是通过hd*x 或 sd*x 表示的，其中 * 表示的是a、b、c …… …… x表示的数字 1、2、3 …… …… hd大多是IDE硬盘；sd大多是SCSI或移动存储；
引导（Boot）：表示引导分区，在上面的例子中 hda1 是引导分区；
Start （开始）：表示的一个分区从X cylinder（磁柱）开始；
End （结束）：表示一个分区到 Y cylinder（磁柱）结束；
id和System 表示的是一个意思，id看起来不太直观，我们要在fdisk 一个分区时，通过指定id来确认分区类型；比如 7表示的就NTFS 分区；这个在fdisk 中要通过t功能来指定。下面的部份会提到；
Blocks（容量）：这是我翻译的，其实不准确，表示的意思的确是容量的意思，其单位是K；一个分区容量的值是由下面的公式而来的；
Blocks = （相应分区End数值 - 相应分区Start数值）x 单位cylinder（磁柱）的容量
所以我们算一下 hda1的 Blocks 的大小 ：
hda1 Blocks=（765-1）x8225.280=6284113.92 K = 6284.113.92M
注：换算单位以硬盘厂家提供的10进位算起，如果以操作系统二进制来算，这个分区容量应该更少一些，得出的这个值和我们通过 fdisk -l 看到的 /dev/hda1的值是大体相当的，因为换算方法不一样，所以也不可能尽可能的精确；再加上分区时的一点损失之类，有时或大或小是存在的；
我们查看分区大小或者文件的时候，还是用十进制来计算比较直观；推算办法是 byte 向前推小数点三位就是K ，K单位的值向前推小数点三位就是M，M向前推小数点三位就是G…… …… 一般也差不了多少；这么算就行；
fdisk 对硬盘及分区的操作，进入fdisk 对硬盘操作阶段，以后再说！
续集
因生产需要，公司增加了第三块磁盘，先对他进行分区等操作，详情如下
公司的第三块盘如下所示
Last login: Thu Nov 28 13:12:21 2013 from 182.151.205.254 [root@pacteralinux ~]# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda1 29954008 17765060 10667336 63% / tmpfs 794380 0 794380 0% /dev/shm /dev/sdb1 72246600 4005880 64570808 6% /mnt/resource [root@pacteralinux ~]# fdisk -l Disk /dev/sda: 32.2 GB, 32212254720 bytes 255 heads, 63 sectors/track, 3916 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: 0x00072ca8 Device Boot Start End Blocks Id System /dev/sda1 * 1 3789 30432256 83 Linux /dev/sda2 3789 3917 1024000 82 Linux swap / Solaris Disk /dev/sdb: 75.2 GB, 75161927680 bytes 255 heads, 63 sectors/track, 9137 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: 0xd1b75611 Device Boot Start End Blocks Id System /dev/sdb1 * 1 9138 73398272 83 Linux Disk /dev/sdc: 536.9 GB, 536870912000 bytes 255 heads, 63 sectors/track, 65270 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
开始分区
1：进入分区状态
[root@pacteralinux ~]# fdisk /dev/sdc
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x05df0a32.
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): m
2:m寻求帮
Command (m for help): m 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)
3:p显示磁盘分区情形
Command (m for help): p Disk /dev/sdc: 536.9 GB, 536870912000 bytes 255 heads, 63 sectors/track, 65270 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: 0x05df0a32 Device Boot Start End Blocks Id System
因磁盘还未开始分区，显示为空
4：n增加第一个新的分区
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-65270, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-65270, default 65270): 48000
输入 e 硬盘为[延伸]分割区(extend)。
输入 p 硬盘为[主要]分割区(primary)。
5:p显示分区情形
Command (m for help): p Disk /dev/sdc: 536.9 GB, 536870912000 bytes 255 heads, 63 sectors/track, 65270 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: 0x05df0a32 Device Boot Start End Blocks Id System /dev/sdc1 1 48000 385559968+ 83 Linux
6：增加第二个分区
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
Partition 1 is already defined. Delete it before re-adding it.
Command (m for help): 2
2: unknown command
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)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (48001-65270, default 48001):
Using default value 48001
Last cylinder, +cylinders or +size{K,M,G} (48001-65270, default 65270):
Using default value 65270
Command (m for help): p
Disk /dev/sdc: 536.9 GB, 536870912000 bytes
255 heads, 63 sectors/track, 65270 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: 0x05df0a32
Device Boot Start End Blocks Id System
/dev/sdc1 1 48000 385559968+ 83 Linux
/dev/sdc2 48001 65270 138721275 83 Linux
7:保存退出
Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
8：查看分区情形
Syncing disks. [root@pacteralinux ~]# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda1 29954008 17765068 10667328 63% / tmpfs 794380 0 794380 0% /dev/shm /dev/sdb1 72246600 4005880 64570808 6% /mnt/resource [root@pacteralinux ~]# fdisk -l Disk /dev/sda: 32.2 GB, 32212254720 bytes 255 heads, 63 sectors/track, 3916 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: 0x00072ca8 Device Boot Start End Blocks Id System /dev/sda1 * 1 3789 30432256 83 Linux /dev/sda2 3789 3917 1024000 82 Linux swap / Solaris Disk /dev/sdb: 75.2 GB, 75161927680 bytes 255 heads, 63 sectors/track, 9137 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: 0xd1b75611 Device Boot Start End Blocks Id System /dev/sdb1 * 1 9138 73398272 83 Linux Disk /dev/sdc: 536.9 GB, 536870912000 bytes 255 heads, 63 sectors/track, 65270 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: 0x05df0a32 Device Boot Start End Blocks Id System /dev/sdc1 1 48000 385559968+ 83 Linux /dev/sdc2 48001 65270 138721275 83 Linux
9：格式化第一个分区，约半个小时
[root@pacteralinux ~]# mkfs.ext4 /dev/sdc1
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
24100864 inodes, 9638××× blocks
4819499 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
2942 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 26 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
10：查看分区情形
Disk /dev/sdc: 536.9 GB, 536870912000 bytes 255 heads, 63 sectors/track, 65270 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: 0x05df0a32 Device Boot Start End Blocks Id System /dev/sdc1 1 48000 385559968+ 83 Linux /dev/sdc2 48001 65270 138721275 83 Linux
11：格式化第二个分区
[root@pacteralinux ~]# mkfs.ext3 /dev/sdc2
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
8675328 inodes, 34680318 blocks
1734015 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
1059 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 33 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
12：查看分区
Disk /dev/sdc: 536.9 GB, 536870912000 bytes 255 heads, 63 sectors/track, 65270 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: 0x05df0a32 Device Boot Start End Blocks Id System /dev/sdc1 1 48000 385559968+ 83 Linux /dev/sdc2 48001 65270 138721275 83 Linux
13：挂载分区
[root@pacteralinux resource]# pwd /mnt/resource [root@pacteralinux resource]# mkdir mysqldataper [root@pacteralinux resource]# mkdir sdc3mnt [root@pacteralinux resource]# mount /dev/sdc1 mysqldat mysqldataper/ mysqldate/ [root@pacteralinux resource]# mount /dev/sdc1 mysqldataper/ [root@pacteralinux resource]# mount /dev/sdc2 sdc3mnt/
14：查看挂在情况
[root@pacteralinux resource]# df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 29G 17G 11G 63% / tmpfs 776M 0 776M 0% /dev/shm /dev/sdb1 69G 3.9G 62G 6% /mnt/resource /dev/sdc1 362G 195M 344G 1% /mnt/resource/mysqldataper /dev/sdc2 131G 188M 124G 1% /mnt/resource/sdc3mnt
注意
硬盘总容量=主分区（包括扩展分区）总容量
扩展分区容量=逻辑分区总容量
在扩展分区上建立逻辑分区
参考：http://www.liusuping.com/ubuntu-linux/linux-fdisk-disk.html