选择要下载的内核版本，https://kernel.ubuntu.com/~kernel-ppa/mainline/

cd /tmp
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.10.4/amd64/linux-headers-5.10.4-051004-generic_5.10.4-051004.202012301142_amd64.deb
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.10.4/amd64/linux-headers-5.10.4-051004_5.10.4-051004.202012301142_all.deb
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.10.4/amd64/linux-image-unsigned-5.10.4-051004-generic_5.10.4-051004.202012301142_amd64.deb
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.10.4/amd64/linux-modules-5.10.4-051004-generic_5.10.4-051004.202012301142_amd64.deb
apt install ./linux-*.deb
rm -rf ./linux-*.deb

查看内核顺序，从0开始，如果包含在submenu内，则写上级次序加下级次序，如1>5。

grep  menuentry /boot/grub/grub.cfg

修改默认启动内核，/etc/default/grub：

GRUB_DEFAULT="1>5"

更新grub：

update-grub