On which partition is my bootloader installed?

Solution 1:

sudo fdisk -l /dev/sda

Where sda is the disk you want to check the partitions, one of them should be listed as boot partition, if you have more then 1 disk there can be other partitions marked as boot, the next logical disk is sdb followed by sdc, etc.

If you have more then a disk and more than 1 partition is marked as boot the booting will be determined by the selected boot device in your BIOS.

Solution 2:

It depends on what you mean by installed. Grub places some files in the /boot directory, which usually is on the same partition as /. It also embeds its core image to the Master Boot Record of the drive, and the following several sectors that are not part of any partition, so in that sense, it is not installed to any partition, but rather to the whole disk.

You can check the output of df to see what partitions you have mounted where. If there is no entry for /boot, then it is part of the root filesystem.