A quick and dirty tips-n-tricks for ansible

A ansible tricks

Variables
==========
predefined variables : 
- inventory_hostname (fqdn) (normally the same as ansible.fqdn)
- inventory_hostname_short 
 
To know the return codes returned by ansible modules, just use plain ansible -vvv to see them : 
ansible -i ~/ansible/arrfab.net/hosts/hosts.cfg -vvv -m copy -a 'src=files/sysinfo dest=/etc/sysinfo' tungstene.arrfab.net
tungstene.arrfab.net | success >> {
    "changed": true, 
    "daisychain_args": "src=files/sysinfo dest=/etc/sysinfo src=/var/tmp/ansible-1351514206.18-224994873189361/sysinfo", 
    "dest": "/etc/sysinfo", 
    "group": "root", 
    "md5sum": "e5e0af8c573543d6beb837ce2ef3e019", 
    "mode": "0644", 
    "owner": "root", 
    "path": "/etc/sysinfo", 
    "secontext": "root:object_r:etc_t", 
    "src": "/var/tmp/ansible-1351514206.18-224994873189361/sysinfo", 
    "state": "file"
}
 so you know you can use ${status.changed} as a variable for logging/mails, etc...
example :
    action: template ... 
    register: mytemplate
 
    action: blablah
    only_if: '${mytemplate.changed}'   #other way of saying only_if: "'${mytemplate.changed}' == 'True'"
 
If your variables is a list containing one iteam on each line , you can use 
register: users
and used ${users.stdout_lines}
 
only_if
=========
 
Test if a variable is defined
only_if: "is_set('${ansible_default_ipv4.gateway}')"
 
String comparison
only_if: "'$declared_user' == 'arrfab'"
 
Misc
only_if: "'$ansible_distribution_version'.startswith('5.')"
 
only_if: "'${blah}' == 'blah' or '${blah}' == 'otherblah'"
only_if: "'${blah}' in ('blah', 'otherblah')"
 
Templates
==========
You can just use variables in jinja2 templates like this : ${my_variable} (attention, variables can't contain . as in my.variable !
Some default variables can be used, like {{ ansible_managed }}, $template_host, $template_uid and $template_path
 
a for loop : 
{% for a in name_of_your_list %} 
  blabla 
{ %endfor %}(name of your list being defined somewhere else in the vars section like name_of_your_list: [one,two,three]
 
{% if 'webserver' in group_names %}
   # some part of a configuration file that only applies to webservers
   
{% endif %}
 
{% for host in groups['app_servers'] %}
   # something that applies to all app servers.
   {{ hostvars[host].ansible_eth0.ipv4.address }}
{% endfor %}
 
# resolv.in by {{ name | upper }}
# for  {{ ansible_eth0.ipv4.address }}
{% if domain is defined -%}
domain {{ domain }}
{% endif -%}
{% for ns in resolvers -%}
nameserver {{ ns }}
{% endfor %}
 
{% if is_cluster_member == True %}
This machine is member of a cluster
{% else %}
{% endif %}
 
Using nesting variables: trying to show ansible_eth0.macaddress, but eth0 itself being a variable defined in the playbook or vars_prompt (user_interface)
user interface: {{ user_interface }}
{% set iface = 'ansible_' + user_interface %}
show: iface = {{ iface }}
show: inventory_hostname = {{ inventory_hostname }}
{% set ifacedata = hostvars[inventory_hostname][iface] %}
mac address of {{ iface }} is {{ ifacedata.macaddress }}