I recently added a hard disk to a linux system in my VMware environment and was waiting to reboot to allow the OS to see the new disk. I then realized that the disks are added as SCSI devices, which should enable hot-swap capabilities.
A little googling and I found the command
echo “- – -” > /sys/class/scsi_host/host*/scan
This rescans the bus and immediately recognised the new disks. Fdisk and mkfs and it was ready to mount