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244 lines
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ReStructuredText
244 lines
6.8 KiB
ReStructuredText
.. _patterns:
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Inventory & Patterns
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====================
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.. image:: http://ansible.cc/docs/_static/ansible_fest_2013.png
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:alt: ansiblefest 2013
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:target: http://www.eventbrite.com/event/5593981750
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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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.. contents:: `Table of contents`
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:depth: 2
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:backlinks: top
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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. Ports listed in any SSH config file won't be read,
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so it is important that you set them if things are not running on the default port::
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badwolf.example.com:5309
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Suppose you have just static IPs and want to set up some aliases that don't live in your host file, or you are connecting through tunnels. You can do things like this::
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jumper ansible_ssh_port=5555 ansible_ssh_host=192.168.1.50
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In the above example, trying to ansible against the host alias "jumper" (which may not even be a real hostname) will contact 192.168.1.50 on port 5555.
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Adding a lot of hosts? In 0.6 and later, if you have a lot of hosts following similar patterns you can do this rather than listing each hostname::
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[webservers]
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www[01:50].example.com
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In 1.0 and later, you can also do this for alphabetic ranges::
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[databases]
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db-[a:f].example.com
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For numeric patterns, leading zeros can be included or removed, as desired. Ranges are inclusive.
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In 1.1 and later, you can also select the connection type and user on a per host basis::
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[targets]
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localhost ansible_connection=local
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other1.example.com ansible_connection=ssh ansible_ssh_user=mpdehaan
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other2.example.com ansible_connection=ssh ansible_ssh_user=mdehaan
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All of these variables can of course also be set outside of the inventory file, in 'host_vars' if you wish
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to keep your inventory file simple.
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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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You can also specify the intersection of two groups::
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webservers:&staging
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You can do combinations::
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webservers:dbservers:!phoenix:&staging
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You can also use variables::
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webservers:!$excluded:&$required
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Individual host names, IPs and 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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separate 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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.. versionadded:: 0.6
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In addition to the storing variables directly in the INI file, host
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and group variables can be stored in individual files relative to the
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inventory file. These 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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.. versionadded:: 0.5
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If you ever have two python interpreters on a system, or your Python version 2 interpreter is not found
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at /usr/bin/python, set an inventory variable called 'ansible_python_interpreter' to the Python
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interpreter path you would like to use.
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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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