Kernel source error during installing DAHDI package

hi everybody
im new user of asterisk im instaling asterisk in a 5.6 centos acording to the orelly ebook
i have successfuly instaled libpri package
in next step i am to install DAHDI , but as it depend on linux kernel source , i have a error:
"You do not appear to have the sources for the 2.6.18-238.el5 kernel installed"
with uname -a this is output : Linux asterisk 2.6.18-238.el5 #1
i try this “sudo yum install kernel-devel-2.6.18-238.el5” but it retern "No package kernel-devel-2.6.18-238.el5 available."
so i try sudo yum install kernel-devel ( whithout version ) and it start to download newer version 2.6.18-308.8.2.el5.i686
but noting off above work give me the result,i have alredy first problem and can`t complet instaling DAHDI
here is a output of rpm -qa | grep ’ kernel ’ :
i did reboot server several time but noting be better
can anybody help me to solve this problem?

Sounds like you need to run “yum update -y; reboot” To install 2.6.18-308.8.2.el5.i686 and then reboot in order to start using the new kernel you just installed.

hi srufell
thank you so mutch
it was best idia
i test: yum update kernel
and it solve the problem