I have an Amazon AWS EC2 Instance running Ubuntu 16.04 LTS. I found that when I used systemctl reboot
or shutdown -r now
from the command line, I wasn't able to reconnect, but when I did a reboot from the Amazon EC2 console, it came back up without any issues.
I then uncovered this in their documentation:
We recommend that you use Amazon EC2 to reboot your instance instead of running the operating system reboot command from your instance.
I've been unsuccessful in finding the "why".