LINUX kernels and their removal

Apparently, McAfee “looks” not just for the running but all LINUX kernels present on a host. So even if I did yum -y upgrade and immediately followed it with another scanner run the process will flag this host as a “failure” because of the presence of the older kernels. It comes back to me now. Years ago, when I worked with the Interactive UNIX (the origin of SUN and AIX) I had to deal with multiple kernels – once or twice I had to remove some to gain back storage capacity on a host.

You may already know the question of today but if you don’t do not worry too much – here it comes: “how to list the kernels and how to remove them from a RedHat machine?”

To list kernels on a RedHat host, execute:

# rpm -qa kernel
kernel-2.6.32-279.19.1.el6.x86_64
kernel-2.6.32-279.14.1.el6.x86_64
kernel-2.6.32-279.11.1.el6.x86_64

To list your current kernel (the short version):

# uname -r
2.6.32-279.19.1.el6.x86_64

To list your current kernel (the long version):

# uname -mrs
Linux 2.6.32-279.19.1.el6.x86_64 x86_64

The last two entries tell us that the running 2.6.32-279.19.1.el6.x86_64 kernel (active) is the most up to date one. So to remove the other (non active) kernels, I have to execute these two steps:

# rpm -e kernel-2.6.32-279.11.1.el6.x86_64
# rpm -e kernel-2.6.32-279.14.1.el6.x86_64

To verify that there is just one kernel left – the one I wanted to keep:

# # rpm -qa kernel
kernel-2.6.32-279.19.1.el6.x86_64

Is there a way to switch kernels on a live RedHat hosts so when it boots next time it uses a different kernel? I know that a kernel selection can be made at boot time. Do you know about any other way? If so please let us all know too, thanks!

I feel, this post would not be complete without this message:

To install kernel packages manually, use "rpm -ivh [package]". Do not use "rpm -Uvh" as that will remove the running kernel binaries from your system. You may use "rpm -e" to remove old kernels after determining that the new kernel functions properly on your system.