第一步：查看當前的內核
root@linux:~# uname -a Linux linux 4.15.0-96-generic #97-Ubuntu SMP Wed Apr 1 03:25:46 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
第二步：查看當前系統中所有內核
root@linux:~# dpkg --get-selections |grep linux console-setup-linux install libselinux1:amd64 install linux-base install linux-firmware install linux-generic install linux-headers-4.15.0-72 install linux-headers-4.15.0-72-generic install linux-headers-4.15.0-91 install linux-headers-4.15.0-91-generic install linux-headers-4.15.0-96 install linux-headers-4.15.0-96-generic install linux-headers-4.15.0-97 install linux-headers-4.15.0-97-generic install linux-headers-generic install linux-image-4.15.0-54-generic deinstall linux-image-4.15.0-55-generic deinstall linux-image-4.15.0-58-generic deinstall linux-image-4.15.0-60-generic deinstall linux-image-4.15.0-62-generic deinstall linux-image-4.15.0-64-generic deinstall linux-image-4.15.0-65-generic deinstall linux-image-4.15.0-66-generic deinstall linux-image-4.15.0-70-generic deinstall linux-image-4.15.0-72-generic install linux-image-4.15.0-74-generic deinstall linux-image-4.15.0-76-generic deinstall linux-image-4.15.0-88-generic deinstall linux-image-4.15.0-91-generic install linux-image-4.15.0-96-generic install linux-image-4.15.0-97-generic install linux-image-generic install linux-modules-4.15.0-54-generic deinstall linux-modules-4.15.0-55-generic deinstall linux-modules-4.15.0-58-generic deinstall linux-modules-4.15.0-60-generic deinstall linux-modules-4.15.0-62-generic deinstall linux-modules-4.15.0-64-generic deinstall linux-modules-4.15.0-65-generic deinstall linux-modules-4.15.0-66-generic deinstall linux-modules-4.15.0-70-generic deinstall linux-modules-4.15.0-72-generic install linux-modules-4.15.0-74-generic deinstall linux-modules-4.15.0-76-generic deinstall linux-modules-4.15.0-88-generic deinstall linux-modules-4.15.0-91-generic install linux-modules-4.15.0-96-generic install linux-modules-4.15.0-97-generic install linux-modules-extra-4.15.0-54-generic deinstall linux-modules-extra-4.15.0-55-generic deinstall linux-modules-extra-4.15.0-58-generic deinstall linux-modules-extra-4.15.0-60-generic deinstall linux-modules-extra-4.15.0-62-generic deinstall linux-modules-extra-4.15.0-64-generic deinstall linux-modules-extra-4.15.0-65-generic deinstall linux-modules-extra-4.15.0-66-generic deinstall linux-modules-extra-4.15.0-70-generic deinstall linux-modules-extra-4.15.0-72-generic install linux-modules-extra-4.15.0-74-generic deinstall linux-modules-extra-4.15.0-76-generic deinstall linux-modules-extra-4.15.0-88-generic deinstall linux-modules-extra-4.15.0-91-generic install linux-modules-extra-4.15.0-96-generic install linux-modules-extra-4.15.0-97-generic install selinux-utils install util-linux install
第三步：移除多余的內核
對於當前沒有用的內核都是多余的，進行刪除
root@linux:~# sudo apt-get remove linux-headers-4.15.0-70 linux-headers-4.15.0-70-generic linux-image-4.15.0-70-generic linux-modules-4.15.0-70-generic linux-modules-extra-4.15.0-70-generic
這樣刪除后會還會在列表中顯示存在，不過是狀態顯示為已經卸載，如果想不顯示徹底清除的話：
root@linux:~# sudo apt-get purge linux-headers-4.15.0-74 linux-headers-4.15.0-74-generic linux-image-4.15.0-74-generic linux-modules-4.15.0-74-generic linux-modules-extra-4.15.0-74-generic
卸載后進行檢查：
root@linux:~# dpkg --get-selections |grep linux console-setup-linux install libselinux1:amd64 install linux-base install linux-firmware install linux-headers-4.15.0-96 install linux-headers-4.15.0-96-generic install linux-image-4.15.0-54-generic deinstall linux-image-4.15.0-55-generic deinstall linux-image-4.15.0-58-generic deinstall linux-image-4.15.0-60-generic deinstall linux-image-4.15.0-62-generic deinstall linux-image-4.15.0-64-generic deinstall linux-image-4.15.0-65-generic deinstall linux-image-4.15.0-66-generic deinstall linux-image-4.15.0-70-generic deinstall linux-image-4.15.0-72-generic deinstall linux-image-4.15.0-74-generic deinstall linux-image-4.15.0-76-generic deinstall linux-image-4.15.0-88-generic deinstall linux-image-4.15.0-91-generic deinstall linux-image-4.15.0-96-generic install linux-image-4.15.0-97-generic deinstall linux-modules-4.15.0-54-generic deinstall linux-modules-4.15.0-55-generic deinstall linux-modules-4.15.0-58-generic deinstall linux-modules-4.15.0-60-generic deinstall linux-modules-4.15.0-62-generic deinstall linux-modules-4.15.0-64-generic deinstall linux-modules-4.15.0-65-generic deinstall linux-modules-4.15.0-66-generic deinstall linux-modules-4.15.0-70-generic deinstall linux-modules-4.15.0-72-generic deinstall linux-modules-4.15.0-74-generic deinstall linux-modules-4.15.0-76-generic deinstall linux-modules-4.15.0-88-generic deinstall linux-modules-4.15.0-91-generic deinstall linux-modules-4.15.0-96-generic install linux-modules-4.15.0-97-generic deinstall linux-modules-extra-4.15.0-54-generic deinstall linux-modules-extra-4.15.0-55-generic deinstall linux-modules-extra-4.15.0-58-generic deinstall linux-modules-extra-4.15.0-60-generic deinstall linux-modules-extra-4.15.0-62-generic deinstall linux-modules-extra-4.15.0-64-generic deinstall linux-modules-extra-4.15.0-65-generic deinstall linux-modules-extra-4.15.0-66-generic deinstall linux-modules-extra-4.15.0-70-generic deinstall linux-modules-extra-4.15.0-72-generic deinstall linux-modules-extra-4.15.0-74-generic deinstall linux-modules-extra-4.15.0-76-generic deinstall linux-modules-extra-4.15.0-88-generic deinstall linux-modules-extra-4.15.0-91-generic deinstall linux-modules-extra-4.15.0-96-generic install linux-modules-extra-4.15.0-97-generic deinstall selinux-utils install util-linux install
狀態為deinstall即為已經卸載
第四步：更新系統引導
刪除內核后需要更新grup移除失效的啟動項
root@linux:~# sudo update-grub #根據情況選擇grub/grub2
======================================================
為什么要刪除多余的內核，ubuntu默認自動更新內核，多余生產環境來說存在不穩定因素，有時候重啟后進入不到系統提示：not syncing : VFS: Unable to mount root
解決辦法就是開機的時候選擇高級模式，選擇之前的低版本的內核，試試那個可以進入到系統中。然后把那個高版本的內核刪除掉，就能解決這個問題。
刪除內核后雖然可以正常就如到系統中，但是系統默認自動更新內核的，為了避免這個情況，我們要關閉內核自動更新，