Create snapshot(backup) from ec2 instance
Please read these links(thanks to them!):
https://n2ws.com/how-to-guides/automate-amazon-ec2-instance-backup.html
https://gregrickaby.com/2013/05/safely-update-an-ubuntu-ec2-instance-on-amazon-aws/
Then upgrade packages:
sudo apt-get update sudo apt-get upgrade
Or upgrade to newer version:
sudo do-release-upgrade