How to bless boot partition for Ubuntu 22.04 on an Intel (2009) MacBookPro

I asked this on the Ubuntu exchange where I personally think it belongs, but they directed me here so please don't close this and tell me to ask there. I'm booting from the Mac OS X Lion installation disk that comes with the laptop and then opening a terminal from inside that. So after trying out different variations, here are the results: bless --device /dev/disk0s1 --setBoot doesn't appear to do anything. Still long timeout on white screen. System still booting afterwards. bless --device /dev/disk0s2 --setBoot same as above. bless --device /dev/disk0s1 --setBoot --legacy still long timeout on white screen. After that system goes to black screen and won't boot into Ubuntu. There are only /dev/disk0s1 and /dev/disk0s2 listed in fdisk for /dev/disk0. I'm assuming /dev/disk0s1 is /boot/efi but I have no idea. I have performed a full-disk install of Ubuntu 22.04 on an old MacBook Pro (MBP 5.2 from 2009, Core 2 Duo) machine completely wiping OSX in the process. I'm now facing the known issue of the 30-second white screen delay on boot. I already figured out I have to use the bless utility to set Ubuntu as the boot partition. My question is what command-line arguments do I have to pass exactly? All examples on the internet make use of the --legacy option and talk about BIOS mode but from what I could figure out my Ubuntu installation is using EFI (the /sys/firmware/efi directory exists ). I assume then that I shouldn't use the --legacy option when blessing the partition. Here's the output of df -h when run in Ubuntu: t30@macbook:~$ df -h tmpfs 770M 1,7M 768M 1% /run /dev/sda2 457G 12G 423G 3% / tmpfs 3,8G 0 3,8G 0% /dev/shm tmpfs 5,0M 4,0K 5,0M 1% /run/lock /dev/sda1 511M 6,1M 505M 2% /boot/efi tmpfs 770M 52K 770M 1% /run/user/1000 I think I should invoke bless like this (replacing /dev/sda1 with whatever it's mounted as under bless). bless --device /dev/sda1 --setBoot Is there a guide or can someone confirm which partition do I have to bless?