Linux將MySQL數據庫目錄掛載至新數據盤


對於Linux系統來說,掛載磁盤的方法其實都大同小異,所以本文以CentOS系統為例,介紹下Linux系統磁盤掛載方法,前面大部分內容源於天翼雲的論壇。
1.查看磁盤情況
使用命令fdisk -l # 列出全部磁盤信息

[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.創建分區
 fdisk /dev/xvde # 對xvde硬盤進行分區
  n  # 創建一個新分區
  p  # 創建一個主分區(e為擴展分區)
  1  # 1表示第一個主分區
  回車  # 從第1柱面開始分區
  回車  # 表示整個xvde全寫入第1分區(若需要將sdb分為多個分區,此時輸入+分區大小)
  P  # 查看下已創建好的分區
  w  # 保存並退出

[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.創建分區文件系統並格式化磁盤
# mkfs.ext4 /dev/xvde1 # 將xvde1以ext4格式進行格式化

[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目錄下面創建文件夾mysql,並且將設備掛載至/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


假如原來文件夾中有文件掛載之后文件會消失並且出現lost+found文件夾,這時不用擔心,可以用umount命令進行取消掛載。
原因是這樣的。
這個牽扯到linux的VFS(虛擬文件系統)機制。登錄以后,你看到的各個目錄,文件都是內核在加載時候構造在內存中的VFS目錄樹,而不是直接看到硬盤上的實際目錄樹。
按照我對http://www.ibm.com/developerworks/cn/linux/l-vfs/這篇文章所描述的粗淺理解,當你掛載某個設備到一個VFS掛載點上時(比如/home),系統就把VFS中的這個掛載點/home指向你最后所掛載的那個設備上。那么你現在訪問該掛載點時,就會看到你最后掛載在此處的設備。而之前所掛載的設備依然在那里,只不過掛載點/home已經不再指向之前的設備。你可以把原來的設備卸載以后掛載到一個新的掛載點上來訪問。

5.將磁盤UUID寫入fstab

對於Linux系統來說,磁盤xvda和xvde的分區是根據系統啟動時識別的先后順序來排列,這樣就會出現一個當主機重啟后,出現跳盤的情況,為了避免此情況的發生,就需要我們將磁盤的UUID信息寫入fstab文件,將分區與磁盤綁定。
1)通過blkid獲得磁盤分區的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)通過vim /etc/fstab在最后一行添加xvde1的磁盤信息

#
# /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.將/var/lib/mysql/下的內容轉移至/home/mysql/,並且在/var/lib/下創建mysql的鏈接,實際目錄其實為/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.驗證一下,通過df命令查看磁盤的使用情況。然后進入mysql命令,創建數據庫test1...,執行之后會在/home/mysql/文件夾下出現數據庫test1,另外使用df命令查看磁盤使用情況。會發現/dev/xvde1使用量在增長。

[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

 


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