My question is, how do I add a (properly-booting) Ubuntu volume to High Sierra's "Startup Disk" Menu?
Running MacOS High Sierra, Windows 10 (Legacy, not EFI), and Ubuntu 18.04 (triple-booting on a 2009 MacPro 4,1 w/ firmware upgrade to 5,1). I installed Ubuntu after Windows using the procedure in this link. I have a second EFI partition for Ubuntu (scroll down for output from diskutil list). I've placed / renamed the boot files so that all three operating systems boot normally using Apple's Startup Manager (holding ALT during bootup) - see this link and this link for guidelines:
However, I cannot select Ubuntu as a bootup option through the "Startup Disk" tool in High Sierra. Initially, the "Startup Disk" menu had no entry for Ubuntu. Then, I followed these steps to create a dummy mach_kernel file and place a SystemVersion.plist from in /System/Library/CoreServices/ my Ubuntu EFI partition. Now, Ubuntu appears in my "Startup Disk" menu, however I cannot select it. "Startup Disk" fails to select Ubuntu, and says, "Running bless to place boot files failed."
Currently, I'm working around this by using the following bless command to boot directly into Ubuntu from High Sierra (only works if csrutil is disabled in Recovery):
sudo bless --device /dev/disk0s5 --setboot --nextonly && sudo reboot
It works for now, but I would appreciate any insights on how to add Ubuntu to High Sierra's "Startup Disk." Thanks!
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
