How can I update the base Raspbian operating system?
Is it safe?
Question is closed for new answers.
Marco Buratto Answered question
In order to udpate the Raspian base OS, login via SSH as root, then:
apt update
apt dist-upgrade
The Raspbian operating system moves from older to newer Debian releases without changing repositories: it may happen that a system update (rarely) brakes the digital signage stack.
Marco Buratto Changed status to publish

As the time of writing, in order to update to a new Raspberry Slideshow release, you have to download the whole .img file, this is because sometimes a system update brakes the digital signage stack and I can guarantee only what I test…
So, please drop me an email if you are entitled for updates.
Marco Buratto Changed status to publish
You can do:
apt update
apt upgrade
For updating only packages that are on the system already, to try minimizing the risk of bricking the system.