我刚刚犯了一个大错误，在我的 linode ubuntu 实例上执行了 apt-get update，然后又执行了 apt-get upgrade。根据以前的经验，升级 GRUB 的任何操作都会终止服务器，因为现有文件中有 linode 特有的特殊添加内容，如果覆盖它们，则无法启动服务器。当弹出消息询问我是否要保留现有文件或覆盖它时，我寻找取消和/或中止的选项。没有。所以我做了下一件最好的事情，按下 CTRL-C。然后跳转到下一部分，询问它应该写入 4 个分区中的哪一个。同样，没有取消或退出的选项，ctrl-C 不起作用。
这是我现在面临的信息：
│ The GRUB boot loader was previously installed to a disk that is no longer │
│ present, or whose unique identifier has changed for some reason. It is important │
│ to make sure that the installed GRUB core image stays in sync with GRUB modules │
│ and grub.cfg. Please check again to make sure that GRUB is written to the │
│ appropriate boot devices. │
│ │
│ If you're unsure which drive is designated as boot drive by your BIOS, it is │
│ often a good idea to install GRUB to all of them. │
│ │
│ Note: it is possible to install GRUB to partition boot records as well, and some │
│ appropriate partitions are offered here. However, this forces GRUB to use the │
│ blocklist mechanism, which makes it less reliable, and therefore is not │
│ recommended. │
│ │
│ GRUB install devices: │
│ │
│ [ ] /dev/sda (686926 MB; QEMU_HARDDISK) │
│ [ ] /dev/sdb (268 MB; QEMU_HARDDISK) │
│ [ ] /dev/sdc (322122 MB; Volume) │
│ [ ] /dev/sda (686926 MB; QEMU_HARDDISK) │
│ <Ok>
显然，我不想写入其中任何一个，但没有这个选项。所以我按了 CTRL-Z，然后按了 ps，并杀死了 pid。
我该怎么做才能回去呢？