Fix grub v2 bootloader configuration on running debian

We have a server running Debian Wheezy. It is connected to a UPS, that's why it basically never went down for years and we never noticed that the grub v2 bootloader could not load the correct kernel anymore (probably since the wheezy update).

Anyway, last week we accidentally shut it down manually and when we started it up again we noticed that the GRUB loader could not find the correct Linux image. Booting up was impossible. I still start sweating thinking about that moment when I realized it will not boot up.

With the help of a live CD called Super Grub2 Disk we could luckily select the correct Debian kernel by hand and boot the system up.

Now we still have an issue, I would like to fix the grub bootloader on the running Debian system now, so the next time one of us accidentally powers off the server, we can just put it back on and GRUB will boot correctly.

• What and where and how can I fix the GRUB bootloader now?


• Maybe just reinstall?


• Change the configuration by hand?

Thanks in advance for any help or pointing me into the correct direction on this.