While doing a „yum update“ this message can be displayed:

Disk Requirements: At least 10MB more space needed on the /boot

That means the /boot is running out of space.

To free up there are at least two options:

Remove kernels manually

Check out your current running Kernel using

uname -a

Check the installed kernel versions with

 yum list installed | grep kernel

And remove not used kernel versions.

Use yum-utils

install yum-util

yum install yum-utils

Remove old kernel versions

package-cleanup --oldkernels --count=2

To make it persistent to only hold two versions change the conf file of yum:

vi /etc/yum.conf
installonly_limit=5