Issue

• How to create a new partition in RHEL 7 without reboot ?
• Disk /dev/sdX is being used for system partition, for example for /boot and / (root). How to create a new partion on it without rebooting the system.
• While creating a new partition with fdisk command, following error is seen. However, partition gets created and could be used.

[root@hostname ~]# fdisk /dev/sda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): p

Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0004886a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    23570431    11272192   8e  Linux LVM

Command (m for help): n
Partition type:
   p   primary (2 primary, 0 extended, 2 free)
   e   extended
Select (default p): p
Partition number (3,4, default 3): 3
First sector (23570432-41943039, default 23570432): 
Using default value 23570432
Last sector, +sectors or +size{K,M,G} (23570432-41943039, default 41943039): +2G
Partition 3 of type Linux and of size 2 GiB is set

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy. <--------
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
[root@hostname ~]# partprobe 
[root@hostname ~]# fdisk -l

Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0004886a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    23570431    11272192   8e  Linux LVM
/dev/sda3        23570432    27764735     2097152   83  Linux

[root@hostname ~]# pvcreate /dev/sda3
  Physical volume "/dev/sda3" successfully created
[root@hostname ~]# pvs
  PV         VG               Fmt  Attr PSize  PFree
  /dev/sda2  rhel_hostname    lvm2 a--  10.75g 4.00m
  /dev/sda3                   lvm2 a--   2.00g 2.00g

• For RHEL 6, when the above mentioned error is seen, the partition table was not read by partprobe.