I had initially tried changing the value of GRUB_DISTRIBUTOR, however grub-update does not take this value as the bootloader id.
If you notice the default GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` produces "Ubuntu", however the default bootloader id is "ubuntu".
I had initially tried changing the value of GRUB_DISTRIBUTOR, however grub-update does not take this value as the bootloader id.
If you notice the default GRUB_DISTRIBUTO R=`lsb_ release -i -s 2> /dev/null || echo Debian` produces "Ubuntu", however the default bootloader id is "ubuntu".