I‘m trying to install RHEL 6 kernel updates and patches using the yum command and getting the following error:

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.

How do I fix this error and install RHEL kernel without increasing /boot size or reinstalling the operating system?

To update kernel, enter:
# yum update kernel
Sample outputs:

Loaded plugins: priorities, product-id, rhnplugin, subscription-manager
Updating Red Hat repositories.
70 packages excluded due to repository priority protections
Setting up Update Process
Resolving Dependencies
There are unfinished transactions remaining. You might consider running yum-complete-transaction first to finish them.
--> Running transaction check
---> Package kernel.x86_64 0:2.6.32-131.2.1.el6 will be installed
--> Processing Dependency: kernel-firmware >= 2.6.32-131.2.1.el6 for package: kernel-2.6.32-131.2.1.el6.x86_64
--> Running transaction check
---> Package kernel-firmware.noarch 0:2.6.32-131.0.15.el6 will be updated
---> Package kernel-firmware.noarch 0:2.6.32-131.2.1.el6 will be an update
--> Finished Dependency Resolution
--> Running transaction check
---> Package kernel.x86_64 0:2.6.32-71.el6 will be erased
--> Finished Dependency Resolution

Dependencies Resolved

=============================================================================================================================================================================================
 Package                              Arch                        Version                                 Repository                                                                    Size
=============================================================================================================================================================================================
Installing:
 kernel                               x86_64                      2.6.32-131.2.1.el6                      rhel-x86_64-server-6                                                          23 M
Removing:
 kernel                               x86_64                      2.6.32-71.el6                           @anaconda-RedHatEnterpriseLinux-201009221801.x86_64/6.0                      112 M
Updating for dependencies:
 kernel-firmware                      noarch                      2.6.32-131.2.1.el6                      rhel-x86_64-server-6                                                         2.5 M

Transaction Summary
=============================================================================================================================================================================================
Install       1 Package(s)
Upgrade       1 Package(s)
Remove        1 Package(s)

Total size: 26 M
Is this ok [y/N]: y
Downloading Packages:
Running rpm_check_debug
Running Transaction Test


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