Turns out it is possible to enter a host name directly into the playbook, so running the playbook with hosts: imac-2.local will work fine. But it's kind of clunky.
A better solution might be defining the playbook's hosts using a variable, then passing in a specific host address via --extra-vars:
# file: user.yml (playbook)
---
- hosts: '{{ target }}'
user: ...
Running the playbook:
ansible-playbook user.yml --extra-vars "target=imac-2.local"
If {{ target }} isn't defined, the playbook does nothing. A group from the hosts file can also be passed through if need be. Overall, this seems like a much safer way to construct a potentially destructive playbook.
Playbook targeting a single host:
$ ansible-playbook user.yml --extra-vars "target=imac-2.local" --list-hosts
playbook: user.yml
play #1 (imac-2.local): host count=1
imac-2.local
Playbook with a group of hosts:
$ ansible-playbook user.yml --extra-vars "target=office" --list-hosts
playbook: user.yml
play #1 (office): host count=3
imac-1.local
imac-2.local
imac-3.local
Forgetting to define hosts is safe!
$ ansible-playbook user.yml --list-hosts
playbook: user.yml
play #1 ({{target}}): host count=0
If you pass the -v flag to ansible-playbook on the command line, you'll see the stdout and stderr for each task executed:
$ ansible-playbook -v playbook.yaml
Ansible also has built-in support for logging. Add the following lines to your ansible configuration file:
[defaults]
log_path=/path/to/logfile
Ansible will look in several places for the config file:
ansible.cfg in the current directory where you ran ansible-playbook~/.ansible.cfg/etc/ansible/ansible.cfg
Best Answer
Have a closer look at Rolling Updates:
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