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198 lines
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ReStructuredText
198 lines
5.2 KiB
ReStructuredText
.. _patterns:
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Inventory & Patterns
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====================
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Ansible works against multiple systems in your infrastructure at the
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same time. It does this by selecting portions of systems listed in
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Ansible's inventory file, which defaults to /etc/ansible/hosts.
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.. _inventoryformat:
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Hosts and Groups
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++++++++++++++++
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The format for /etc/ansible/hosts is an INI format and looks like this::
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mail.example.com
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[webservers]
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foo.example.com
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bar.example.com
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[dbservers]
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one.example.com
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two.example.com
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three.example.com
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The things in brackets are group names. You don't have to have them,
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but they are useful.
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If you have hosts that run on non-standard SSH ports you can put the port number
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after the hostname with a colon.
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four.example.com:5309
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Selecting Targets
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+++++++++++++++++
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We'll go over how to use the command line in :doc:`examples` section, however, basically it looks like this::
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ansible <pattern_goes_here> -m <module_name> -a <arguments>
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Such as::
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ansible webservers -m service -a "name=httpd state=restarted"
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Within :doc:`playbooks`, these patterns can be used for even greater purposes.
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Anyway, to use Ansible, you'll first need to know how to tell Ansible which hosts in your inventory file to talk to.
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This is done by designating particular host names or groups of hosts.
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The following patterns target all hosts in the inventory file::
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all
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*
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Basically 'all' is an alias for '*'. It is also possible to address a specific host or hosts::
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one.example.com
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one.example.com:two.example.com
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192.168.1.50
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192.168.1.*
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The following patterns address one or more groups, which are denoted
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with the aforementioned bracket headers in the inventory file::
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webservers
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webservers:dbservers
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You can exclude groups as well, for instance, all webservers not in Phoenix::
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webservers:!phoenix
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Individual host names (or IPs), but not groups, can also be referenced using
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wildcards::
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*.example.com
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*.com
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It's also ok to mix wildcard patterns and groups at the same time::
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one*.com:dbservers
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Easy enough. See :doc:`examples` and then :doc:`playbooks` for how to do things to selected hosts.
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Host Variables
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++++++++++++++
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It is easy to assign variables to hosts that will be used later in playbooks::
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[atlanta]
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host1 http_port=80 maxRequestsPerChild=808
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host2 http_port=303 maxRequestsPerChild=909
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Group Variables
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+++++++++++++++
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Variables can also be applied to an entire group at once::
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[atlanta]
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host1
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host2
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[atlanta:vars]
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ntp_server=ntp.atlanta.example.com
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proxy=proxy.atlanta.example.com
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Groups of Groups, and Group Variables
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+++++++++++++++++++++++++++++++++++++
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It is also possible to make groups of groups and assign
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variables to groups. These variables can be used by /usr/bin/ansible-playbook, but not
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/usr/bin/ansible::
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[atlanta]
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host1
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host2
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[raleigh]
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host2
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host3
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[southeast:children]
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atlanta
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raleigh
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[southeast:vars]
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some_server=foo.southeast.example.com
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halon_system_timeout=30
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self_destruct_countdown=60
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escape_pods=2
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[usa:children]
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southeast
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northeast
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southwest
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southeast
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If you need to store lists or hash data, or prefer to keep host and group specific variables
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seperate from the inventory file, see the next section.
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Splitting Out Host and Group Specific Data
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++++++++++++++++++++++++++++++++++++++++++
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In Ansible 0.6 and later, in addition to the storing variables directly in the INI file, host and
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group variables can be stored in individual files relative to the inventory file. These
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variable files are in YAML format.
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Assuming the inventory file path is::
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/etc/ansible/hosts
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If the host is named 'foosball', and in groups 'raleigh' and 'webservers', variables
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in YAML files at the following locations will be made available to the host::
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/etc/ansible/group_vars/raleigh
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/etc/ansible/group_vars/webservers
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/etc/ansible/host_vars/foosball
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For instance, suppose you have hosts grouped by datacenter, and each datacenter
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uses some different servers. The data in the groupfile '/etc/ansible/group_vars/raleigh' for
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the 'raleigh' group might look like::
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---
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ntp_server: acme.example.org
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database_server: storage.example.org
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It is ok if these files do not exist, this is an optional feature.
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Tip: Keeping your inventory file and variables in a git repo (or other version control)
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is an excellent way to track changes to your inventory and host variables.
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Tip: If you ever have two python interpreters on a system, set a variable called 'ansible_python_interpreter' to
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the Python interpreter path you would like to use.
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YAML Inventory
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++++++++++++++
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Ansible's YAML inventory format is deprecated and will be removed in Ansible 0.7. Ansible 0.6 includes
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a `conversion script <https://github.com/ansible/ansible/blob/devel/examples/scripts/yaml_to_ini.py>`_.
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Usage::
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yaml_to_ini.py /etc/ansible/hosts
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.. seealso::
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:doc:`examples`
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Examples of basic commands
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:doc:`playbooks`
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Learning ansible's configuration management language
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`Mailing List <http://groups.google.com/group/ansible-project>`_
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Questions? Help? Ideas? Stop by the list on Google Groups
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`irc.freenode.net <http://irc.freenode.net>`_
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#ansible IRC chat channel
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