Complementary to this handbook, if you maintain one or more debian servers it is useful to learn and adopt a configuration management tool -- assuming you are not already using another state management technique that gives you even more control.
The time invested to learn and automate repetitive configuration or admin tasks (upgrades, installing dependencies, deploying a new version of your app, etc) through ansible and ansible-playbook pays for itself pretty fast. For common tasks there are often high level modules that provide a simple declarative interface to non-interactively configure the desired state compared to using the underlying command line tools directly. E.g.. installing/upgrading packages with apt: https://docs.ansible.com/ansible/latest/modules/apt_module.h...
The time invested to learn and automate repetitive configuration or admin tasks (upgrades, installing dependencies, deploying a new version of your app, etc) through ansible and ansible-playbook pays for itself pretty fast. For common tasks there are often high level modules that provide a simple declarative interface to non-interactively configure the desired state compared to using the underlying command line tools directly. E.g.. installing/upgrading packages with apt: https://docs.ansible.com/ansible/latest/modules/apt_module.h...