Kernel Cleanup Using YUM

Table of Contents

This document will show you how to set the RHEL7 hostname (Redhat 7 or CentOS 7) based machine. If you have built your new RHEL7 based machine and have now got a bit stuck over how to change the hostname from localhost.localdomain to what ever you want this is the how to for you.

Check Installed Kernels #

The command below will list all kernels that are currently installed on the system

[root@server ~]# rpm -q kernel
kernel-3.10.0-514.el7.x86_64
kernel-3.10.0-514.6.1.el7.x86_64
kernel-3.10.0-693.5.2.el7.x86_64
kernel-3.10.0-693.11.1.el7.x86_64
kernel-3.10.0-693.11.6.el7.x86_64

The uname command will show which kernel is currently Running

[root@server ~]# uname -r
3.10.0-693.11.6.el7.x86_64

Remove Old Kernels #

Next we will install the yum-utils package which contains the tools we need to limit the number of installed kernels.

Install Utilities #

[root@server ~]# yum install yum-utils

Set Kernels to Keep #

Package-cleanup is used to set how many packages will be kept. The command below sets 2 old kernels to be kept.

[root@server ~]# package-cleanup --oldkernels --count=2
Loaded plugins: fastestmirror
--> Running transaction check
---> Package kernel.x86_64 0:3.10.0-514.el7 will be erased
---> Package kernel.x86_64 0:3.10.0-514.6.1.el7 will be erased
---> Package kernel.x86_64 0:3.10.0-693.5.2.el7 will be erased
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package       Arch          Version                     Repository        Size
================================================================================
Removing:
 kernel        x86_64        3.10.0-514.el7              @anaconda        148 M
 kernel        x86_64        3.10.0-514.6.1.el7          @updates         148 M
 kernel        x86_64        3.10.0-693.5.2.el7          @updates          59 M

Transaction Summary
================================================================================
Remove  3 Packages

Installed size: 355 M
Is this ok [y/N]: y
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Erasing    : kernel.x86_64                            1/3
  Erasing    : kernel.x86_64                            2/3
  Erasing    : kernel.x86_64                            3/3
  Verifying  : kernel-3.10.0-693.5.2.el7.x86_64         1/3
  Verifying  : kernel-3.10.0-514.6.1.el7.x86_64         2/3
  Verifying  : kernel-3.10.0-514.el7.x86_64             3/3

Removed:
  kernel.x86_64 0:3.10.0-514.el7 kernel.x86_64 0:3.10.0-514.6.1.el7 kernel.x86_64 0:3.10.0-693.5.2.el7

Complete!

Kernel Count Check #

Next check how many kernels have been left installed, it should be 2

[root@server ~]# rpm -q kernel
kernel-3.10.0-693.11.1.el7.x86_64
kernel-3.10.0-693.11.6.el7.x86_64

Update Installed Kernels Permanently #

Next we need to set the number of kernels to stay at two permanently.

Edit /etc/yum.conf or /etc/dnf/dnf.conf and set installonly_limit:

installonly_limit=2

Thats it, now when ever we update the system, there will only be the last two kernels left on the system.