不用重启在CentOS / RHEL 虚拟机中添加一块新硬盘

有时候我们在服务器或者虚拟机中添加了一块新硬盘，但是用fdisk -l 却看不到新添加的硬盘，这时候就需要重启服务器来识别新添加的硬盘
但是大家知道服务器是不能随便重启的，那么有什么好的方法可以不用重启就能识别新的硬盘吗？
答案是有的

步骤
在线添加一块磁盘

至于详细的虚拟机添加磁盘细节这里就不说了，都很简单，New Hard Disk就是新添加的磁盘



这时我们用fdisk -l 是看不到新添加的磁盘的

[root@steven ~]# fdisk -l

Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 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: 0x0009a3b5

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1 * 1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        2611    20458496   8e  Linux LVM

Disk /dev/sdb: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 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: 0xf27bd8ef

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2               1          65      522081    5  Extended
/dev/sdb5               1          26      208782   8e  Linux LVM

Disk /dev/mapper/VolGroup-lv_root: 19.0 GB, 19042140160 bytes
255 heads, 63 sectors/track, 2315 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


Disk /dev/mapper/VolGroup-lv_swap: 2113 MB, 2113929216 bytes
255 heads, 63 sectors/track, 257 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

确定主机总线号，磁盘是有总线连接着的

[root@steven ~]# ls /sys/class/scsi_host/
host0  host1  host2

重新扫描SCSI总线来添加设备，因为添加的是SCSI磁盘，所以扫描的是SCSI总线

[root@steven ~]# echo "- - -" > /sys/class/scsi_host/host0/scan
[root@steven ~]# echo "- - -" > /sys/class/scsi_host/host1/scan
[root@steven ~]# echo "- - -" > /sys/class/scsi_host/host2/scan

验证

[root@steven ~]# fdisk -l

Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 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: 0x0009a3b5

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1 * 1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        2611    20458496   8e  Linux LVM

Disk /dev/sdb: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 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: 0xf27bd8ef

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb2               1          65      522081    5  Extended
/dev/sdb5               1          26      208782   8e  Linux LVM

Disk /dev/mapper/VolGroup-lv_root: 19.0 GB, 19042140160 bytes
255 heads, 63 sectors/track, 2315 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


Disk /dev/mapper/VolGroup-lv_swap: 2113 MB, 2113929216 bytes
255 heads, 63 sectors/track, 257 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


Disk /dev/sdc: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 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

可以看到，Disk /dev/sdc就是新添加的磁盘 ，这样就实现了不重启在CentOS / RHEL 虚拟机中添加一块新硬盘