Make sure Parallels Desktop is not running. If it is running, the commands below will still create a console window.
From Terminal.app, use the Parallels command line: prlctl
# List available VMs
prlctl list --all
# Start a VM using its name
prlctl start UbuntuServer
# Stop the VM
prlctl stop UbuntuServer
# Pause and Resume
prlctl pause UbuntuServer
prlctl resume UbuntuServer
# Reset and Restart
prlctl reset UbuntuServer
prlctl restart UbuntuServer