Linux将MySQL数据库目录挂载至新数据盘

对于Linux系统来说，挂载磁盘的方法其实都大同小异，所以本文以CentOS系统为例，介绍下Linux系统磁盘挂载方法，前面大部分内容源于天翼云的论坛。
1.查看磁盘情况
使用命令fdisk -l # 列出全部磁盘信息

[root@qxyw ~]# fdisk -l

Disk /dev/xvda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 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: 0x0008a9a5

Device Boot          Start         End      Blocks   Id  System
/dev/xvda1               1         523     4194304   82  Linux swap / Solaris
Partition 1 does not end on cylinder boundary.
/dev/xvda2   *         523        5222    37747712   83  Linux

Disk /dev/xvde: 322.1 GB, 322122547200 bytes
255 heads, 63 sectors/track, 39162 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

2.创建分区
 fdisk /dev/xvde # 对xvde硬盘进行分区
  n  # 创建一个新分区
  p  # 创建一个主分区（e为扩展分区）
  1  # 1表示第一个主分区
  回车  # 从第1柱面开始分区
  回车  # 表示整个xvde全写入第1分区（若需要将sdb分为多个分区，此时输入+分区大小）
  P  # 查看下已创建好的分区
  w  # 保存并退出

[root@qxyw ~]# fdisk /dev/xvde
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x590ca8b1.
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): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-39162, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-39162, default 39162):
Using default value 39162

Command (m for help): p

Disk /dev/xvde: 322.1 GB, 322122547200 bytes
255 heads, 63 sectors/track, 39162 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: 0x590ca8b1

    Device Boot      Start         End      Blocks   Id  System
/dev/xvde1               1       39162   314568733+  83  Linux

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

Calling ioctl() to re-read partition table.
Syncing disks.

3.创建分区文件系统并格式化磁盘
# mkfs.ext4 /dev/xvde1 # 将xvde1以ext4格式进行格式化

[root@qxyw ~]# mkfs.ext4 xvde1
mke2fs 1.41.12 (17-May-2010)
Could not stat xvde1 --- No such file or directory

The device apparently does not exist; did you specify it correctly?
[root@qxyw ~]# mkfs.ext4 /dev/xvde1
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
19660800 inodes, 78642183 blocks
3932109 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
2400 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

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 25 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

4.在home目录下面创建文件夹mysql，并且将设备挂载至/home/mysql。

[root@qxyw home]# mount /dev/xvde1 /home/mysql
[root@qxyw home]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/xvda2             36G  2.4G   32G   7% /
tmpfs                 3.9G     0  3.9G   0% /dev/shm
/dev/xvde1            296G  191M  281G   1% /home/mysql

假如原来文件夹中有文件挂载之后文件会消失并且出现lost+found文件夹，这时不用担心，可以用umount命令进行取消挂载。
原因是这样的。
这个牵扯到linux的VFS（虚拟文件系统）机制。登录以后，你看到的各个目录，文件都是内核在加载时候构造在内存中的VFS目录树，而不是直接看到硬盘上的实际目录树。
按照我对http://www.ibm.com/developerworks/cn/linux/l-vfs/这篇文章所描述的粗浅理解，当你挂载某个设备到一个VFS挂载点上时(比如/home），系统就把VFS中的这个挂载点/home指向你最后所挂载的那个设备上。那么你现在访问该挂载点时，就会看到你最后挂载在此处的设备。而之前所挂载的设备依然在那里，只不过挂载点/home已经不再指向之前的设备。你可以把原来的设备卸载以后挂载到一个新的挂载点上来访问。

5.将磁盘UUID写入fstab

对于Linux系统来说，磁盘xvda和xvde的分区是根据系统启动时识别的先后顺序来排列，这样就会出现一个当主机重启后，出现跳盘的情况，为了避免此情况的发生，就需要我们将磁盘的UUID信息写入fstab文件，将分区与磁盘绑定。
1）通过blkid获得磁盘分区的UUID

[root@qxyw ~]# blkid
/dev/xvda1: UUID="5546dd0c-ef40-451b-b266-df8ef3a49967" TYPE="swap"
/dev/xvda2: UUID="77fc0962-b3cf-400a-8903-0632e077fa09" TYPE="ext3"
/dev/xvde1: UUID="1d17945b-c369-42de-85a8-47217d24d3e5" TYPE="ext4"

2）通过vim /etc/fstab在最后一行添加xvde1的磁盘信息

#
# /etc/fstab
# Created by anaconda on Thu Jan 12 02:47:21 2017
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=77fc0962-b3cf-400a-8903-0632e077fa09 /                       ext3    defaults        1 1
UUID=5546dd0c-ef40-451b-b266-df8ef3a49967 swap                    swap    defaults        0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
UUID=d17945b-c369-42de-85a8-47217d24d3e5 /home/mysql ext4 defaults      0 0

6.将/var/lib/mysql/下的内容转移至/home/mysql/，并且在/var/lib/下创建mysql的链接，实际目录其实为/home/mysql

[root@qxyw /]# cd home
[root@qxyw home]# mkdir mysql
[root@qxyw home]# mv /var/lib/mysql/* /home/mysql
[root@qxyw home]# ln /home/mysql /var/lib/mysql

7.验证一下，通过df命令查看磁盘的使用情况。然后进入mysql命令，创建数据库test1...，执行之后会在/home/mysql/文件夹下出现数据库test1，另外使用df命令查看磁盘使用情况。会发现/dev/xvde1使用量在增长。

[root@qxyw mysql]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/xvda2            37155392   2417608  32850400   7% /
tmpfs                  4018012         0   4018012   0% /dev/shm
/dev/xvde1           309633052    217092 293687524   1% /home/mysql