Rescanning a Linux SCSI device after it is changed on a VM Host

Sometimes when you change the logical drive of a VM from the Host, the device size is not reflected in the Guest. So attempts to use the extra space with fdisk or the NVM tools will not "see" the extra disc.

This is because the Linux kernel doesn't notice it, because it's not looking. Linux usually only scans this at boot time. But you probably can't reboot a server if it's live, so what do you do?

To tell Linux to have another look now, you just need to poke it:

echo 1 > /sys/bus/scsi/devices/1:0:0:0/rescan

Where "1:0:0:0" is the device ID for the disc. Linux will rescan immediately and then the extra space will appear for you to use.