Re-read The Partition Table Without Rebooting Linux System
If you are using hot swappable hard disk and created new partition using fdisk then you need to reboot Linux based system to get partition recognized. Without reboot you will NOT able to create filesystem on your newly created or modified partitions with the mke2fs command.
However with partprobe command you should able to
create a new file system without rebooting the box. It
is a program that informs the operating system kernel of
partition table changes, by requesting that the
operating system re-read the partition table.
After the fdisk command session (which makes changes to partition table) just type the following command:
# partprobe /dev/sdX
Replace /dev/sdX or /dev/hdX with actual device name. Now you will able to create filesystem on new partition with the mke2fs command.