If you run "apt-get -y install foo" that means that you want "foo" to be installed. If it's already installed, it just does nothing.

In Ansible, you'd use "apt: name=foo state=present" which does exactly the same thing as the apt-get command, but requires a web search to figure out how to write (assuming you know normal Linux system usage but haven't memorized Ansible).

The only differences seem to be that Ansible tells you whether the command made a change or not, and that you can parse the Ansible configuration with an external tool (assuming there are no loops/variable/etc.), but both of these things don't really seem that useful in practice.

not really. If you do that it means that you want to update foo to the latest version the system knows about.

And other commands fail if the thing they are supposed to to is already done. Like `adducer`. So you could still run it and assume a failure to mean "the user already exists" - but it could of course also mean: "the user didn't exist, but creating it failed".

Then you start to have a look at the exit code which may be different between the two cases.

But every command behaves differently, so you need to learn all of this.

With Ansible (or puppet), the syntax is always the same and the actually needed operations are abstracted away.

You missed more Ansible strengths, like detecting changes and restarting only affected services for example. Show me the idempotent shell script which does apt-get to install some dependency, updates some configuration file, and then starts or restarts a service depending on both the current state of the service (was it already running?) and whether the apt-get or config file change actuallly modified things.

Then scale that up. A lot.

There is even more. If you care to learn it before dismissing it.

I still use Salt instead of shell scripts, but that's mostly to have the authenticated/encrypted channels and only have to push my code to one place to run it globally.