How to: Linux delete or remove kernel

Q. I have multiple versions installed and I need to save disk space. I am using Cent OS Linux. How can I delete or remove a Linux kernel from my Linux distribution ?

A. Linux Kernel and related files are stored in following locations:
=> /boot – Stores actual kernel and related file such system man and initrd images,

=> /etc or /boot/grub – Stores grub.conf file (most distro use /boot/grub these days).

=> /iib/modules/KERNEL-VERSION/* – Linux device drivers (modules)

If kernel is installed using binary package system such as rpm, yum, up2date, apt-get etc you can remove with following commands:

Rpm based distro – Red Hat/CentOS/Fedora Core/Suse Linux

First find out all installed kernel version with following command:
# rpm -qa | grep kernel-smp
or
# rpm -qa | grep kernel
Output:

kernel-smp-2.6.9-42.EL
kernel-smp-2.6.9-42.0.3.EL
kernel-smp-2.6.9-42.0.8.EL

I’ve total 3 different kernel installed. To remove kernel-smp-2.6.9-42.EL type command:
# rpm -e kernel-smp-2.6.9-42.EL
OR
# rpm -vv -e kernel-smp-2.6.9-42.EL

.deb based distro – Debian or Ubuntu Linux

Again find out all installed kernel version:
$ dpkg --list | grep kernel-image
Output:

ii  kernel-image-2.4.27-2-386   2.4.27-10sarge1             Linux kernel image for version 2.4.27 on 386
ii  kernel-image-2.6.8-2-686    2.6.8-16sarge1              Linux kernel image for version 2.6.8 on PPro

Now remove kernel-image-2.4.27-2-386 with apt-get command itself:
# apt-get remove kernel-image-2.4.27-2-386
OR
$ sudo apt-get remove kernel-image-2.4.27-2-386

If you have custom compiled kernel you need to remove following files/dirs:

• /boot/vmlinuz*KERNEL-VERSION*
• /boot/initrd*KERNEL-VERSION*
• /boot/System-map*KERNEL-VERSION*
• /boot/config-*KERNEL-VERSION*
• /lib/modules/*KERNEL-VERSION*/
• Update grub configuration file /etc/grub.conf or /boot/grub/menu.lst to point to correct kernel version.

Caution: Removing working kernel may result into unstable / non- bootable Linux server system.