You need to install yum-utils, which is an assortment of utilities that integrate with yum to make it more powerful and easier to use, by extending its original features in several different ways.
# yum install yum-utils
One of these utilities is package-cleanup which you can use to delete old kernel as shown below, the count flag is used to specify the number of kernels you want to leave on the system.
# package-cleanup --oldkernels --count=2
Loaded plugins: fastestmirror, langpacks, product-id, versionlock --> Running transaction check ---> Package kernel.x86_64 0:3.10.0-229.el7 will be erased ---> Package kernel.x86_64 0:3.10.0-229.14.1.el7 will be erased ---> Package kernel-devel.x86_64 0:3.10.0-229.1.2.el7 will be erased ---> Package kernel-devel.x86_64 0:3.10.0-229.14.1.el7 will be erased --> Finished Dependency Resolution Dependencies Resolved =============================================================================================================================================================================================== Package Arch Version Repository Size =============================================================================================================================================================================================== Removing: kernel x86_64 3.10.0-229.el7 @anaconda 131 M kernel x86_64 3.10.0-229.14.1.el7 @updates 131 M kernel-devel x86_64 3.10.0-229.1.2.el7 @updates 32 M kernel-devel x86_64 3.10.0-229.14.1.el7 @updates 32 M Transaction Summary =============================================================================================================================================================================================== Remove 4 Packages Installed size: 326 M Is this ok [y/N]: y Downloading packages: Running transaction check Running transaction test Transaction test succeeded Running transaction Erasing : kernel-devel.x86_64 1/4 Erasing : kernel.x86_64 2/4 Erasing : kernel-devel.x86_64 3/4 Erasing : kernel.x86_64 4/4 Loading mirror speeds from cached hostfile * base: centos.mirror.snu.edu.in * epel: repo.ugm.ac.id * extras: centos.mirror.snu.edu.in * rpmforge: kartolo.sby.datautama.net.id * updates: centos.mirror.snu.edu.in Verifying : kernel-3.10.0-229.el7.x86_64 1/4 Verifying : kernel-devel-3.10.0-229.14.1.el7.x86_64 2/4 Verifying : kernel-3.10.0-229.14.1.el7.x86_64 3/4 Verifying : kernel-devel-3.10.0-229.1.2.el7.x86_64 4/4 Removed: kernel.x86_64 0:3.10.0-229.el7 kernel.x86_64 0:3.10.0-229.14.1.el7 kernel-devel.x86_64 0:3.10.0-229.1.2.el7 kernel-devel.x86_64 0:3.10.0-229.14.1.el7 Complete!
Important: After running the above command, it will remove all old/unused kernels and keep the current running and old latest kernel as backup.
Removing Old/Unused Kernels on Fedora
Fedora now uses dnf package manager, a new version of yum package manager, so you need to use this command below to remove old kernels on Fedora.
# dnf remove $(dnf repoquery --installonly --latest-limit 2 -q)
Another alternative way to remove old kernels automatically is setting the kernel limit in yum.conf file as shown.
installonly_limit=2 #set kernel count
Save and close the file. The next time you run an update, only two kernels will be left on the system.