Ubuntu 20.04 LTS修改内核版本

参考：https://cloud.tencent.com/developer/article/2121264

11. 修改内核版本

11.1 查看自己的grub版本

# grub-install --version
grub-install (GRUB) 2.04-1ubuntu26.16

11.2 查看现有的内核版本（完全版）

# grep 'menuentry' /boot/grub/grub.cfg
 [ x"${feature_menuentry_id}" = xy ]; then
  menuentry_id_option="--id"
  menuentry_id_option=""
export menuentry_id_option
menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-2c4a365d-d766-4ed8-bc34-e66c06859e45' {}
submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45' {}
        menuentry 'Ubuntu, with Linux 5.4.0-144-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.4.0-144-generic-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45' {}
        menuentry 'Ubuntu, with Linux 5.4.0-144-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.4.0-144-generic-recovery-2c4a365d-d766-4ed8-bc34-e66c06859e45' {}
        menuentry 'Ubuntu, with Linux 5.4.0-125-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.4.0-125-generic-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45' {}
        menuentry 'Ubuntu, with Linux 5.4.0-125-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.4.0-125-generic-recovery-2c4a365d-d766-4ed8-bc34-e66c06859e45' {}

11.3 修改grub

# vim /etc/default/grub

将GRUB_DEFAULT=0修改为：

GRUB_DEFAULT="Ubuntu, with Linux 5.4.0-125-generic"

# update-grub
...
...
Warning: Please don't use old title `Ubuntu, with Linux 5.4.0-125-generic' for GRUB_DEFAULT, use 'Advanced options for Ubuntu>Ubuntu, with Linux 5.4.0-125-generic' (for versions before 2.00) or 'gnulinux-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45>gnulinux-5.4.0-125-generic-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45' (for 2.00 or later)
...
...

再将GRUB_DEFAULT修改为：

GRUB_DEFAULT="gnulinux-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45>gnulinux-5.4.0-125-generic-advanced-2c4a365d-d766-4ed8-bc34-e66c06859e45"

再次执行update-grub不应再看到任何警告提示，重启后验证内核版本。

11.4 删除原来的内核

查看当前的所有已安装的内核：

# dpkg --get-selections | grep linux-image
linux-image-5.4.0-125-generic                   install
linux-image-5.4.0-144-generic                   install
linux-image-generic                             install

删除内核：

# apt remove linux-image-5.4.0-144-generic

# apt autoremove

# dpkg -P linux-image-5.4.0-144-generic

11.5 最后别忘记修改/etc/default/grub的GRUB_DEFAULT为0，以及update-grub。