How to delete redundant kernels in Ubuntu

Step 1: View the current kernel

rew $ uname -a
Linux rew 4.15.0-42-generic #45~16.04.1-Ubuntu SMP Mon Nov 1913:02:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

The currently used version is: 4.15.0-42-generic

Step 2: View all cores

rew $ dpkg --get-selections | grep linux
console-setup-linux           install
libselinux1:amd64            install
libselinux1:i386            install
linux-base               install
linux-firmware             install
linux-generic-hwe-16.04         install
linux-headers-4.15.0-42         install
linux-headers-4.15.0-39         install
linux-headers-4.15.0-39-generic     install
linux-headers-4.15.0-42-generic     install
linux-headers-generic-hwe-16.04     install
linux-image-4.15.0-39-generic      install
linux-image-4.15.0-42-generic      install
linux-image-generic-hwe-16.04      install
linux-libc-dev:amd64          install
linux-libc-dev:i386           install
linux-modules-4.15.0-39-generic     install
linux-modules-4.15.0-42-generic     install
linux-modules-extra-4.15.0-39-generic  install
linux-modules-extra-4.15.0-42-generic  install
linux-sound-base            install
pptp-linux               install
syslinux                install
syslinux-common             install
syslinux-legacy             install
util-linux               install

Step 3: Remove redundant cores

All 39 versions are redundant to me, delete them:

rew $ sudo apt-get remove \
linux-headers-4.15.0-39 \
linux-headers-4.15.0-39-generic \
linux-image-4.15.0-39-generic \
linux-modules-4.15.0-39-generic \
linux-modules-extra-4.15.0-39-generic

Check again after uninstalling:

rew $ dpkg --get-selections | grep linux
console-setup-linux           install
libselinux1:amd64            install
libselinux1:i386            install
linux-base               install
linux-firmware             install
linux-generic-hwe-16.04         install
linux-headers-4.15.0-42         install
linux-headers-4.15.0-42-generic     install
linux-headers-generic-hwe-16.04     install
linux-image-4.15.0-39-generic      deinstall
linux-image-4.15.0-42-generic      install
linux-image-generic-hwe-16.04      install
linux-libc-dev:amd64          install
linux-libc-dev:i386           install
linux-modules-4.15.0-39-generic     deinstall
linux-modules-4.15.0-42-generic     install
linux-modules-extra-4.15.0-39-generic  deinstall
linux-modules-extra-4.15.0-42-generic  install
linux-sound-base            install
pptp-linux               install
syslinux                install
syslinux-common             install
syslinux-legacy             install
util-linux               install

If the status is deinstall, it has been uninstalled. If you feel uncomfortable, you can use purge to delete the configuration file and clean the kernel list.

rew $ sudo apt-get purge \
linux-headers-4.15.0-39 \
linux-headers-4.15.0-39-generic \
linux-image-4.15.0-39-generic \
linux-modules-4.15.0-39-generic \
linux-modules-extra-4.15.0-39-generic

Step 4: Update system boot

After deleting the kernel, grub needs to be updated to remove invalid startup items

rew $ sudo update-grub #Choose grub according to the situation/grub2

The above is the whole content of this article, I hope it will be helpful to everyone's study.