Windows – hfs-bless / Booting into MacOS / Windows directly from Ubuntu (triple boot, MacPro 4,1 -> 5,1)

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Currently I have MacOS High Sierra, Windows 10 (Legacy, not EFI), and Ubuntu 18.04 triple-booting on a 2009 MacPro 4,1 (firmware upgraded to 5,1). I installed Ubuntu after Windows using the procedure described here. All three operating systems boot normally using Apple's Startup Manager (holding ALT during bootup). My question is, how do I boot directly into Ubuntu, Windows 10, and MacOS HS from each of the other partitions?

I can use the terminal to boot directly into Windows 10 or Ubuntu from MacOS using the following commands (output of diskutil list at bottom of post for reference). For Windows 10:

sudo bless --legacy --device /dev/disk0s4 --setboot --nextonly && sudo reboot

and for Ubuntu EFI:

sudo bless --device /dev/disk0s5 --setboot --nextonly && sudo reboot

But is there an equivalent terminal command to "bless" my MacOS or windows partition from Ubuntu 18.04? I'm aware of 'hfs-bless' in mactel-utils, but this does not appear to support Ubuntu 18.04 (only previous Ubuntu versions). Is it possible to install mactel-utils in Ubuntu 18.04? If not, is there an Ubuntu equivalent of MacOs' "Startup Disk" or bless so that Ubuntu will restart into my Windows 10 or Mac partition?

Output of diskutil list:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            1.5 TB     disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data BOOTCAMP                290.3 GB   disk0s4
   5:                  Apple_HFS Ubuntu                  200.3 MB   disk0s5
   6:                 Linux Swap                         8.0 GB     disk0s6
   7:           Linux Filesystem                         201.5 GB   disk0s7

Apple's Startup Manager

Best Answer

I know it's an old thread but for your information: you can still download mactel-boot .deb package from this link http://ppa.launchpad.net/detly/mactel-utils/ubuntu/pool/main/m/mactel-boot/mactel-boot_0.9-1~xenial_amd64.deb (Xenial version). It's install smoothly in Ubuntu 2018.04.3 LTS correctly and, apparently, works.