转自：https://kerneltalks.com/disk-management/how-to-rescan-disk-in-linux-after-extending-vmware-disk/

当对linux虚拟机在原磁盘增加空间后，往往需要reboot才发现新的空间，今天找到一个方法，并测试成功：

echo 1>/sys/class/block/sdd/device/rescan
OR
echo 1>/sys/class/scsi_device/X:X:X:X/device/block/device/rescan

很多文档提到使用如下方法：
echo "- - -" > /sys/class/scsi_host/host0/scan

经验证此方法失败，看到有其它文档说明如下：

Note : Sending “– – -” to /sys/class/scsi_host/hostX/scan is scanning SCSI host adapters for new disks on every channel (first -), every target (second -), and every device i.e. disk/lun (third -) i.e. CTD format. This will only help to scan when new devices are attached to the system. It will not help us to re-scan already identified devices.

That’s why we have to send “1” to /sys/class/block/XYZ/device/rescan to respective SCSI block device to refresh device information like the size. So this will be helpful here since our device is already identified by the kernel but we want the kernel to re-read its new size and update itself accordingly.