I've done some searching online without luck, hoping that one of you mac virtuosos might know the answer. Is there a command that will reboot a Mac into recovery mode? (I know I can do Command + R but Im looking for a terminal command to do this.)
You can do that using the following command:
sudo nvram "recovery-boot-mode=unused" sudo reboot
This sets a firmware variable in nvram indicating that you want to start Recovery on the next boot, and then reboots the machine.
When done in Recovery mode, run the following from the Terminal in Recovery mode:
sudo nvram -d recovery-boot-mode
This deletes the firmware variable so that the next boot is a normal boot.
If Recovery boot fails and you cannot progress, you could also remove the firmware variable by holding down the keys Command, Option, P and R during boot. This resets the nvram and thus the firmware variable.