我的服务器是一家托管公司的 Xen VPS，支持有限，因此我与他们谈论此事时没有取得多大成功。
当我设置服务器时，他们唯一可用的映像是 16.04.02 LTS，因此我使用了它，然后立即将其升级到 20.04.2 LTS，但是它仍然运行内核 4.4.0-75，我相信它是从 2017 年开始的，我担心潜在的安全问题。
已安装的内核包：
# dpkg --list | grep linux-image
ii linux-image-4.4.0-75-generic 4.4.0-75.96 amd64 Linux kernel image for version 4.4.0 on 64 bit x86 SMP
ii linux-image-5.4.0-72-generic 5.4.0-72.80 amd64 Signed kernel image generic
ii linux-image-5.4.0-73-generic 5.4.0-73.82 amd64 Signed kernel image generic
ii linux-image-extra-4.4.0-75-generic 4.4.0-75.96 amd64 Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP
ii linux-image-generic 5.4.0.73.76 amd64 Generic Linux kernel image
ii linux-image-virtual 5.4.0.73.76 amd64 Virtual Linux kernel image
我运行了“update-grub”并重新启动，由于服务器无法启动，停机了几个小时。重新启动时我通过串行控制台连接，但 Grub 计时器太短，我无法与菜单交互，当它尝试启动到 5.4.0-73 时，它失败了，并将我踢出控制台，阻止我重新进入。如果我使用 VPS 管理中的“启动”选项，如果我非常快，我可以回到控制台片刻，然后它再次将我踢出，但正如提到的，Grub 超时太短，无法与其交互。
我向 VPS 公司开具了一张工单，他们恢复了服务器，但他们所做的只是将其设置为重新启动到 4.4.0-75，并说较新的内核“似乎不起作用”
我更改了 Grub 配置以延长超时时间，然后尝试再次重新启动。现在我可以与 Grub 菜单交互，并更清楚地了解正在发生的事情。当我尝试启动 5.4.0-73 或 5.4.0-72（包括恢复模式）时，没有错误消息，VM 只是默默关闭，我必须再次启动它。
启动失败时不会生成任何日志
也许 VPS 系统和较新的内核分支之间存在一些不兼容性，所以我想我可以继续使用 4.4，只是为了安全起见，只需移动一个较新的版本，但我找不到软件包
packages.ubuntu.com 上的大多数链接都已失效
就像我想我可能需要查看 Xenial 包，但链接的页面https://packages.ubuntu.com/xenial-updates/是无效链接
我在运行 update-grub 时也遇到了错误，但我不知道这些错误是否与此有关；在 Google 上搜索了很多，但没有找到解决方案或有用的信息
# update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
Found linux image: /boot/vmlinuz-5.4.0-73-generic
Found initrd image: /boot/initrd.img-5.4.0-73-generic
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
Found linux image: /boot/vmlinuz-5.4.0-72-generic
Found initrd image: /boot/initrd.img-5.4.0-72-generic
Found linux image: /boot/vmlinuz-4.4.0-75-generic
Found initrd image: /boot/initrd.img-4.4.0-75-generic
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
/usr/sbin/grub-probe: warning: disk does not exist, so falling back to partition device /dev/xvda1.
done