Sorry for reviving this old thread. While searching for an answer by myself, I didn't find much really useful posts on MR, just this question. If anyone is still interested in the topic, here I share some hints.
There are numerous articles around the web about installing Sierra in VirtualBox. Most of them didn't work for me while installing a guest VM macOS Sierra 10.12.6 on VirtualBox 5.2.8 on host macOS Sierra 10.12.6.
All the instructions, making an ISO image of the Sierra Installer App, failed for me at the point of booting Sierra VM in VirtualBox with one of the following symptoms:
1.) Prohibitory Symbol with a lot of scrambled text
2.) hangs on boot sequence around gIOScreenLockState 3, hs 0, bs 0, now 0, sm 0x0
3.) VM was booting into VirtualBox UEFI interactive Shell
I don't know if there is a correct way, making just an ISO image that would install and boot successfully. Some users stated, it was working until macOS Sierra 10.12.3 and macOS Sierra 10.12.4 started to introduce problems.
Finding a different approach seemed logical. That was, trying to write a Virtual Disk Image (VDI) 'directly' of the Sierra Installer App. On GitHub I found these interesting sites:
https://github.com/jonanh/osx-vm-templates
https://github.com/timsutton/osx-vm-templates
I downloaded those two bash scripts:
prepare_vdi.sh
prepare_ovf.sh
I commented out some parts (references to create_firstboot_pkg.sh) of code in prepare_vdi.sh.
Whole part:
- # Import shared code to generate first boot pkgs
First and last section in part:
- # Build our post-installation pkg that will create a user and enable ssh
Additionally I changed the parts of prepare_vdi.sh to my liking so that I wouldn't need to pass any command line switches:
- # Parse the optional command line switches
- # Flags
Finally running prepare_vdi.sh and then prepare_ovf.sh, gave me a macOS Sierra 10.12.6 VM that was working. Sure, there might be easier or better approaches for this task. I hope bumping this old thread can help the OP or at least others that are searching for some solution.