Could you make script for autorun bitcoin daemon after start VPS?
You can probably just use cron for this... it has settings that allow you to run commands after startup.
The best is still to make use of the provided
bitcoind.service file for systemd.
Most likely it is already bundled in the ubuntu's bitcoind package.
As root, the following should work:
# cp bitcoind.service /lib/systemd/system/bitcoind.service
# systemctl enable bitcoind
# systemctl start bitcoind
# systemctl status bitcoind
It will register it in systemd & making it as a service to start at boot. There is no need of a third party script.