Deleting the old kernels lost on your hard drive
Spring Cleaning

© Lead Image © Amy Walters, 123RF.com
When you update the kernel, the old version remains on the disk. If you clean up, the reward is several hundred megabytes of free disk space.
All is flux; nothing stays still. This adage also applies to long-term Linux versions such as Ubuntu LTS and CentOS. The most important reasons for regular updates are security and troubleshooting. And the kernel develops, too. Recent patches for Spectre and Meltdown are good examples of important kernel changes that had to arrive through system updates.
But what happens to the old kernel after an update? First of all, the kernel is a normal software package. It is thus managed through the package management system for your Linux variant. In the case of a Debian or Ubuntu system, this means Apt; in the case of Red Hat-based systems, RPM and its friends Yum and DNF.
If you take a closer look, you'll see that there is no update for the kernel package: The package manager simply adds the new version to the system without deleting the previous version. Often several old versions will remain on the disk (see the box "Turning Back the Clock"), which requires a large amount of disk space.
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