Linux /boot: Out of Disk Space While Installing Package kernel

Transaction Check Error:
  installing package kernel-2.6.32-131.2.1.el6.x86_64 needs 8MB on the /boot filesystem

Error Summary
-------------
Disk Requirements:
  At least 8MB more space needed on the /boot filesystem.

It means /boot partition is out of disk space. You can verify this with the df command itself, enter:
# df -H /boot
To fix this problem deleted all old kernel. To list all installed kernel, enter:
# rpm -qa | grep kernel
Sample outputs:

  kernel-2.6.32-71.el6.x86_64
  kernel-2.6.32-71.29.1.el6.x86_64
  kernel-2.6.32-131.0.15.el6.x86_64

Erase older version, enter:
# rpm -e kernel-2.6.32-71.el6.x86_64 kernel-2.6.32-71.29.1.el6.x86_64
# df -H /boot
Now, try installing the new updated kernel:
# yum -y update kernel
Also apply other updates from RHN, enter:
# yum -y update
Finally, reboot the system, enter:
# reboot