The boot partition is where the kernel information and boot files of the linux operating system are stored. Many Linux installation tutorials suggest that the boot partition should be divided into about 200M. However, some people may not have enough boot partition because they are using the LTS version. Ubuntu system.
LTS means Long Term Support, which means long-term support. Ubuntu will provide three-year updates for such systems, such as Ubuntu kernel updates and so on. In addition, I am using the latest version of Ubuntu20.04, which has been updated two or three times in the past half a month. The problem is that the Ubuntu system will not delete the old version after updating the kernel, resulting in smaller and smaller boot partition capacity, so the old version needs to be manually deleted.
$ df -h /boot View boot partition usage 
$ dpkg --get-selections |grep linux-image View the kernel image currently installed in the system
$ uname -r View the kernel version of the local system
$ sudo apt-get purge linux-image-5.13.0.25-generic Delete the specified image version or header version
Note: The remove command can also be deleted, but the purge command will delete the kernel and its configuration information together, while the remove command only uninstalls the kernel, and the relevant configuration information is still saved in the system.