CentOS在不重启的情况下为其虚拟机添加新硬盘的教程

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                 　　通常在你在虚拟机中添加一块新硬盘时，你可能会看到新硬盘没有自动加载。这是因为连接到硬盘的SCSI总线需要重新扫描来使得新硬盘可见。这里有一个简单的命令来重新扫描SCSI总线和SCSI设备。下面这几步在CentOS  7 和RHEL 7 中测试过。
　　在ESXi或者vCenter中添加一块新的20G硬盘：
　　显示当前磁盘分区：
　　代码如下:
　　[root@centos7 ~]# fdisk -l
Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes
　　Disk label type: dos
　　Disk identifier: 0x0006b96a
　　Device Boot Start End Blocks Id System
　　/dev/sda1 * 2048 1026047 512000 83 Linux
　　/dev/sda2 1026048 62914559 30944256 8e Linux LVM
　　Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304  sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes
　　Disk /dev/mapper/centos-root: 29.5 GB, 29536288768 bytes, 57688064  sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes
　　确定主机总线号
　　代码如下:
　　[root@centos7 ~]# ls /sys/class/scsi_host/
　　host0 host1 host2
　　重新扫描SCSI总线来添加设备
　　代码如下:
　　[root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host0/scan
　　[root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host1/scan
　　[root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host2/scan
　　验证磁盘和分区并确保20GB硬盘已经添加了。在本例中，出现了下面这行 “Disk /dev/sdb: 21.5 GB, 21474836480  bytes, 41943040 sectors” 并且可以确认没有重启服务器就添加了新盘：
　　代码如下:
　　[root@centos7 ~]# fdisk -l
　　Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes
　　Disk label type: dos
　　Disk identifier: 0x0006b96a
　　Device Boot Start End Blocks Id System
　　/dev/sda1 * 2048 1026047 512000 83 Linux
　　/dev/sda2 1026048 62914559 30944256 8e Linux LVM
　　Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304  sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes
　　Disk /dev/mapper/centos-root: 29.5 GB, 29536288768 bytes, 57688064  sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes
　　Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
　　Units = sectors of 1 * 512 = 512 bytes
　　Sector size (logical/physical): 512 bytes / 512 bytes
　　I/O size (minimum/optimal): 512 bytes / 512 bytes