In ansible, how do I specify an exclusion set of hosts in a playbook?

Question

With command line patterns, you can specify patterns like "all,!ntpservers" but I can't figure out how to specify this in a playbook. I'm regularly running into cases where I have to install a client on all machines except the server.

Answer 1

You specify the hosts for a playbook on the line that begins with hosts:.

From the documentation:

The hosts line is a list of one or more groups or host patterns, separated by colons, as described in the Working with Patterns documentation.

For example:

---
- hosts: all,!ntpservers
  tasks:
    # ... your tasks here
  roles:
    # ... etc etc etc

These roles and tasks will be appled to all hosts except ntpservers.