In this step we will list all currently installed kernels:
# rpm -q kernel
Using package-cleanup command which is a part of yum-utils package we can uninstall any number of old kernels automatically. As an example using –oldkernels –count=2 option with package-cleanup command the command will remove all unused kernel while keeping last three most recent kernel versions installed.
Let’s remove all kernels expect the latest currently loaded kernel:
package-cleanup --oldkernels --count=1 Loaded plugins: fastestmirror --> Running transaction check ---> Package kernel.x86_64 0:3.10.0-327.36.3.el7 will be erased ---> Package kernel.x86_64 0:3.10.0-514.2.2.el7 will be erased --> Finished Dependency Resolution Dependencies Resolved ======================================================================================================================================================================================================================= Package Arch Version Repository Size ======================================================================================================================================================================================================================= Removing: kernel x86_64 3.10.0-327.36.3.el7 @anaconda 136 M kernel x86_64 3.10.0-514.2.2.el7 @updates 148 M
Configure yum to auto-remove old kernels
By default CentOS will keep last 5 kernels installed on your system. This behavior is defined by installonly_limit=5 line within /etc/yum.conf file. Update the /etc/yum.conf configuration file appropriately to keep desired number of old kernels on your system after update. The minimum value to be set is 2. Example of /etc/yum.conf configuration file to keep only last two kernel versions:
[main] cachedir=/var/cache/yum/$basearch/$releasever keepcache=0 debuglevel=2 logfile=/var/log/yum.log exactarch=1 obsoletes=1 gpgcheck=1 plugins=1 installonly_limit=2 bugtracker_url=http://bugs.centos.org/set_project.php?project_id=23&ref=http://bugs.centos.org/bug_report_page.php?category=yum distroverpkg=centos-release
./ :https://linuxconfig.org/how-to-remove-old-unused-kernels-on-centos-linux