In my memory, the Linux kernel only reads partition table information at system initialization. So it needs reboot to get the new partition table info after re-partitioning. Until I see partprobe recently, I change my mind.

partprobe is a program that informs the operating system kernel of partition table changes, by requesting that the operating system re-read the partition table. That means, disk re-partitioning now can be handled "on-the-fly".

After re-partitioning you disk with fdisk/parted, just type:

# partprobe

# partprobe [device_node]

PS: if no partition of the disk is mounted, use:

# blockdev --rereadpt [device_node]

Reference

1. GNU Parted official web.
2. Man page of partprobe.
3. Man page of blockdev.