partprobe is a program that tells the operating system kernel about the partition table changes by requesting the operating system to re-read the partition table again so that you do not have to reboot for the changes to appear on the partition table. A reboot is what the system administrators just cannot do on the system running web server's so for them this command is of utmost importance.
The command and its option
partprobe [-d] [-s] [-h] [device]
-d : Don't update the partition table, it is what you normally don't intend to do when you change the partition tables
-s : for showing summary of the devices and their partitions
-h: To show summary of options
device: The hardware device /dev/hda , /dev/hdb etc