Today I was running some yum updates and wanted to verify that everything went through fine by making sure I had a new kernel. To my surprise I noticed that CentOS was still running 2.6.32-431.5.1.el6.x86_64 even though it looked as though 2.6.32-431.23.3.el6 was installed.

Indeed 2.6.32-431.23.3.el6 shows up in /etc/grub.conf but not in the upstart boot options. Any ideas why?

In the update log it says:

---> Package kernel-firmware.noarch 0:2.6.32-431.5.1.el6 will be updated
---> Package kernel-firmware.noarch 0:2.6.32-431.23.3.el6 will be an update

Could this be the reason? What does "will be an update" mean?

My /etc/grub.conf:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/mapper/VolGroup00-root
#          initrd /initrd-[generic-]version.img
#boot=/dev/vda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
password --encrypted $1$auui(i$sODM4ni/Zts9IlMWu.wWF/
title CentOS (2.6.32-431.23.3.el6.x86_64)
    root (hd0,0)
    kernel /vmlinuz-2.6.32-431.23.3.el6.x86_64 ro root=/dev/mapper/VolGroup00-root rd_NO_LUKS LANG=en_US.UTF-8  KEYBOARDTYPE=pc KEYTABLE=sv-latin1 rd_NO_MD rd_LVM_LV=VolGroup00/swap SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=VolGroup00/root rd_NO_DM rhgb quiet rhgb quiet audit=1
    initrd /initramfs-2.6.32-431.23.3.el6.x86_64.img
title CentOS (2.6.32-431.5.1.el6.x86_64)
    root (hd0,0)
    kernel /vmlinuz-2.6.32-431.5.1.el6.x86_64 ro root=/dev/mapper/VolGroup00-root rd_NO_LUKS LANG=en_US.UTF-8  KEYBOARDTYPE=pc KEYTABLE=sv-latin1 rd_NO_MD rd_LVM_LV=VolGroup00/swap SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=VolGroup00/root rd_NO_DM rhgb quiet rhgb quiet audit=1
    initrd /initramfs-2.6.32-431.5.1.el6.x86_64.img
title CentOS (2.6.32-431.el6.x86_64)
    root (hd0,0)
    kernel /vmlinuz-2.6.32-431.el6.x86_64 ro root=/dev/mapper/VolGroup00-root rd_NO_LUKS LANG=en_US.UTF-8  KEYBOARDTYPE=pc KEYTABLE=sv-latin1 rd_NO_MD rd_LVM_LV=VolGroup00/swap SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=VolGroup00/root rd_NO_DM rhgb quiet rhgb quiet audit=1
    initrd /initramfs-2.6.32-431.el6.x86_64.img