ansible/docsite/rst/intro_inventory.rst

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.. _inventory:
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Inventory
=========
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.. contents:: Topics
Ansible works against multiple systems in your infrastructure at the
same time. It does this by selecting portions of systems listed in
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Ansible's inventory file, which defaults to being saved in
the location /etc/ansible/hosts.
Not only is this inventory configurable, but you can also use
multiple inventory files at the same time (explained below) and also
pull inventory from dynamic or cloud sources, as described in :doc:`intro_dynamic_inventory`.
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.. _inventoryformat:
Hosts and Groups
++++++++++++++++
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The format for /etc/ansible/hosts is an INI-like format and looks like this::
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mail.example.com
[webservers]
foo.example.com
bar.example.com
[dbservers]
one.example.com
two.example.com
three.example.com
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The things in brackets are group names, which are used in classifying systems
and deciding what systems you are controlling at what times and for what purpose.
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It is ok to put systems in more than one group, for instance a server could be both a webserver and a dbserver.
If you do, note that variables will come from all of the groups they are a member of, and variable precedence is detailed in a later chapter.
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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 your SSH config file won't be used with the paramiko
connection but will be used with the openssh connection.
To make things explicit, it is suggested 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 live in your host file, or you are connecting through tunnels. You can also describe hosts like this::
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jumper ansible_port=5555 ansible_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. Note that this is using a feature of the inventory file to define some special variables. Generally speaking this is not the best
way to define variables that describe your system policy, but we'll share suggestions on doing this later. We're just getting started.
Adding a lot of hosts? 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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For numeric patterns, leading zeros can be included or removed, as desired. Ranges are inclusive. You can also define alphabetic ranges::
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[databases]
db-[a:f].example.com
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You can also select the connection type and user on a per host basis::
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[targets]
localhost ansible_connection=local
other1.example.com ansible_connection=ssh ansible_user=mpdehaan
other2.example.com ansible_connection=ssh ansible_user=mdehaan
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As mentioned above, setting these in the inventory file is only a shorthand, and we'll discuss how to store them in individual files
in the 'host_vars' directory a bit later on.
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.. _host_variables:
Host Variables
++++++++++++++
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As alluded to above, it is easy to assign variables to hosts that will be used later in playbooks::
[atlanta]
host1 http_port=80 maxRequestsPerChild=808
host2 http_port=303 maxRequestsPerChild=909
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.. _group_variables:
Group Variables
+++++++++++++++
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Variables can also be applied to an entire group at once::
[atlanta]
host1
host2
[atlanta:vars]
ntp_server=ntp.atlanta.example.com
proxy=proxy.atlanta.example.com
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.. _subgroups:
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Groups of Groups, and Group Variables
+++++++++++++++++++++++++++++++++++++
It is also possible to make groups of groups using the ``:children`` suffix. Just like above, you can apply variables using ``:vars``::
[atlanta]
host1
host2
[raleigh]
host2
host3
[southeast:children]
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atlanta
raleigh
[southeast:vars]
some_server=foo.southeast.example.com
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halon_system_timeout=30
self_destruct_countdown=60
escape_pods=2
[usa:children]
southeast
northeast
southwest
northwest
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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_vars:
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Splitting Out Host and Group Specific Data
++++++++++++++++++++++++++++++++++++++++++
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The preferred practice in Ansible is actually not to store variables in the main inventory file.
In addition to storing variables directly in the INI file, host
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. Valid file extensions include '.yml', '.yaml', '.json',
or no file extension. See :doc:`YAMLSyntax` if you are new to YAML.
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Assuming the inventory file path is::
/etc/ansible/hosts
If the host is named 'foosball', and in groups 'raleigh' and 'webservers', variables
in YAML files at the following locations will be made available to the host::
/etc/ansible/group_vars/raleigh # can optionally end in '.yml', '.yaml', or '.json'
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/etc/ansible/group_vars/webservers
/etc/ansible/host_vars/foosball
For instance, suppose you have hosts grouped by datacenter, and each datacenter
uses some different servers. The data in the groupfile '/etc/ansible/group_vars/raleigh' for
the 'raleigh' group might look like::
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---
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ntp_server: acme.example.org
database_server: storage.example.org
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It is ok if these files do not exist, as this is an optional feature.
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As an advanced use-case, you can create *directories* named after your groups or hosts, and
Ansible will read all the files in these directories. An example with the 'raleigh' group::
/etc/ansible/group_vars/raleigh/db_settings
/etc/ansible/group_vars/raleigh/cluster_settings
All hosts that are in the 'raleigh' group will have the variables defined in these files
available to them. This can be very useful to keep your variables organized when a single
file starts to be too big, or when you want to use :doc:`Ansible Vault<playbooks_vault>` on a part of a group's
variables. Note that this only works on Ansible 1.4 or later.
Tip: In Ansible 1.2 or later the group_vars/ and host_vars/ directories can exist in either
the playbook directory OR the inventory directory. If both paths exist, variables in the playbook
directory will override variables set in the inventory directory.
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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.. _behavioral_parameters:
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List of Behavioral Inventory Parameters
+++++++++++++++++++++++++++++++++++++++
As alluded to above, setting the following variables controls how ansible interacts with remote hosts.
Host connection::
ansible_connection
Connection type to the host. Candidates are local, smart, ssh or paramiko. The default is smart.
SSH connection::
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ansible_host
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The name of the host to connect to, if different from the alias you wish to give to it.
ansible_port
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The ssh port number, if not 22
ansible_user
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The default ssh user name to use.
ansible_ssh_pass
The ssh password to use (this is insecure, we strongly recommend using --ask-pass or SSH keys)
ansible_ssh_private_key_file
Private key file used by ssh. Useful if using multiple keys and you don't want to use SSH agent.
Squashed commit of the following: commit 9921bb9d2002e136c030ff337c14f8b7eab0fc72 Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Mon Aug 10 20:19:44 2015 +0530 Document --ssh-extra-args command-line option commit 8b25595e7b1cc3658803d0821fbf498c18ee608a Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Thu Aug 13 13:24:57 2015 +0530 Don't disable GSSAPI/Pubkey authentication when using --ask-pass This commit is based on a bug report and PR by kolbyjack (#6846) which was subsequently closed and rebased as #11690. The original problem was: «The password on the delegated host is different from the one I provided on the command line, so it had to use the pubkey, and the main host doesn't have a pubkey on it yet, so it had to use the password.» (This commit is revised and included here because #11690 would conflict with the changes in #11908 otherwise.) Closes #11690 commit 119d0323892c65e8169ae57e42bbe8e3517551a3 Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Thu Aug 13 11:16:42 2015 +0530 Be more explicit about why SSH arguments are added This adds vvvvv log messages that spell out in detail where each SSH command-line argument is obtained from. Unfortunately, we can't be sure if, say, self._play_context.remote_user is obtained from ANSIBLE_REMOTE_USER in the environment, remote_user in ansible.cfg, -u on the command line, or an ansible_ssh_user setting in the inventory or on a task or play. In some cases, e.g. timeout, we can't even be sure if it was set by the user or just a default. Nevertheless, on the theory that at five v's you can use all the hints available, I've mentioned the possible sources in the log messages. Note that this caveat applies only to the arguments that ssh.py adds by itself. In the case of ssh_args and ssh_extra_args, we know where they are from, and say so, though we can't say WHERE in the inventory they may be set (e.g. in host_vars or group_vars etc.). commit b605c285baf505f75f0b7d73cb76b00d4723d02e Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Tue Aug 11 15:19:43 2015 +0530 Add a FAQ entry about ansible_ssh_extra_args commit 49f8edd035cd28dd1cf8945f44ec3d55212910bd Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Mon Aug 10 20:48:50 2015 +0530 Allow ansible_ssh_args to be set as an inventory variable Before this change, ssh_args could be set only in the [ssh_connection] section of ansible.cfg, and was applied to all hosts. Now it's possible to set ansible_ssh_args as an inventory variable (directly, or through group_vars or host_vars) to selectively override the global setting. Note that the default ControlPath settings are applied only if ssh_args is not set, and this is true of ansible_ssh_args as well. So if you want to override ssh_args but continue to set ControlPath, you'll need to repeat the appropriate options when setting ansible_ssh_args. (If you only need to add options to the default ssh_args, you may be able to use the ansible_ssh_extra_args inventory variable instead.) commit 37c1a5b6794cee29a7809ad056a86365a2c0f886 Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Mon Aug 10 19:42:30 2015 +0530 Allow overriding ansible_ssh_extra_args on the command-line This patch makes it possible to do: ansible somehost -m setup \ --ssh-extra-args '-o ProxyCommand="ssh -W %h:%p -q user@bouncer.example.com"' This overrides the inventory setting, if any, of ansible_ssh_extra_args. Based on a patch originally by @Richard2ndQuadrant. commit b023ace8a8a7ce6800e29129a27ebe8bf6bd38e0 Author: Abhijit Menon-Sen <ams@2ndQuadrant.com> Date: Mon Aug 10 19:06:19 2015 +0530 Add an ansible_ssh_extra_args inventory variable This can be used to configure a per-host or per-group ProxyCommand to connect to hosts through a jumphost, e.g.: inventory: [gatewayed] foo ansible_ssh_host=192.0.2.1 group_vars/gatewayed.yml: ansible_ssh_extra_args: '-o ProxyCommand="ssh -W %h:%p -q bounceuser@gateway.example.com"' Note that this variable is used in addition to any ssh_args configured in the [ssh_connection] section of ansible.cfg (so you don't need to repeat the ControlPath settings in ansible_ssh_extra_args).
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ansible_ssh_args
This setting overrides any ``ssh_args`` configured in ``ansible.cfg``.
ansible_ssh_extra_args
Additional arguments for ssh. Useful to configure a ``ProxyCommand`` for a certain host (or group).
This is used in addition to any ``ssh_args`` configured in ``ansible.cfg`` or the inventory.
ansible_ssh_pipelining
Determines whether or not to use SSH pipelining. This can override the
``pipelining`` setting in ``ansible.cfg``.
Privilege escalation (see :doc:`Ansible Privilege Escalation<become>` for further details)::
ansible_become
Equivalent to ansible_sudo or ansible_su, allows to force privilege escalation
ansible_become_method
Allows to set privilege escalation method
ansible_become_user
Equivalent to ansible_sudo_user or ansible_su_user, allows to set the user you become through privilege escalation
ansible_become_pass
Equivalent to ansible_sudo_pass or ansible_su_pass, allows you to set the privilege escalation password
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Remote host environment parameters::
ansible_shell_type
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The shell type of the target system. Commands are formatted using 'sh'-style syntax by default. Setting this to 'csh' or 'fish' will cause commands executed on target systems to follow those shell's syntax instead.
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ansible_python_interpreter
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The target host python path. This is useful for systems with more
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than one Python or not located at "/usr/bin/python" such as \*BSD, or where /usr/bin/python
is not a 2.X series Python. We do not use the "/usr/bin/env" mechanism as that requires the remote user's
path to be set right and also assumes the "python" executable is named python, where the executable might
be named something like "python26".
ansible\_\*\_interpreter
Works for anything such as ruby or perl and works just like ansible_python_interpreter.
This replaces shebang of modules which will run on that host.
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Examples from a host file::
some_host ansible_port=2222 ansible_user=manager
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aws_host ansible_ssh_private_key_file=/home/example/.ssh/aws.pem
freebsd_host ansible_python_interpreter=/usr/local/bin/python
ruby_module_host ansible_ruby_interpreter=/usr/bin/ruby.1.9.3
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.. seealso::
:doc:`intro_dynamic_inventory`
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Pulling inventory from dynamic sources, such as cloud providers
:doc:`intro_adhoc`
Examples of basic commands
:doc:`playbooks`
Learning Ansibles configuration, deployment, and orchestration language.
`Mailing List <http://groups.google.com/group/ansible-project>`_
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