Sorry, this is just a little complicated but I need to include this detail to explain the problem.
I'm in the process of recuperating an old Netbook which has two ssd's (4 GB and 16 GB).
I had initially installed Haiku (r42190) on the smaller ssd which, AFAIK, put BootManager into /dev/sda1 rather than the mbr of the first disk.
Nevertheless, it still booted fine.
Then, I installed Ubuntu in two partitions (/ and /home) on the larger ssd. Because the installer was unable to install Grub to the mbr of /dev/sda (some kind of incompatibility with the BFS on this disk), I instead installed it in /dev/sdb1 (the root partition rather than the mbr of the larger disk).
Then I went back to Haiku and used BootManager to create a boot menu.
However, BootManager would not install on the smaller disk's mbr (saying that no space was available -- which I don't understand as nothing should have been in this mbr) so I had to install it in the mbr of the larger disk.
This enabled me to boot to the Haiku bootloader and select either Ubuntu or Haiku. Great.
But, I wanted Grub as my bootloader.
So, back in Ubuntu, I deleted everything on the smaller disk, created a new partition /dev/sda1, installed Grub to the mbr of the smaller disk and then removed the Haiku bootloader from the mbr of the larger disk by running
# dd if=/dev/null of=/dev/sdb bs=446 count=1
I was a bit surprised when the output from this command showed zero input and output but, nevertheless, I proceeded to reboot.
However, I was amazed to find that, on reboot, the BootManager menu showed up again, fully functional, and NOT Grub.
I then, in Ubuntu, ran the boot_info_script which confirmed that Grub2 was installed without any problems in the mbr of /dev/sda.
I'm baffled.
Can anybody suggest how I might get rid of BootManager so that I can get Grub to do the bootloading?