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90 lines
3.3 KiB
ReStructuredText
90 lines
3.3 KiB
ReStructuredText
Using Lookups
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=============
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Lookup plugins allow access of data in Ansible from outside sources. This can include the filesystem
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but also external datastores. These values are then made available using the standard templating system
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in Ansible, and are typically used to load variables or templates with information from those systems.
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.. note:: This is considered an advanced feature, and many users will probably not rely on these features.
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Intro to Lookups: Getting File Contents
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```````````````````````````````````````
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The file lookup is the most basic lookup type.
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Contents can be read off the filesystem as follows::
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- hosts: all
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vars:
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contents: "{{ lookup('file', '/etc/foo.txt') }}"
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tasks:
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- debug: msg="the value of foo.txt is {{ contents }}"
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The Password Lookup
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```````````````````
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``password`` generates a random plaintext password and store it in
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a file at a given filepath. Support for crypted save modes (as with vars_prompt) is pending. If the
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file exists previously, it will retrieve its contents, behaving just like with_file. Usage of variables like "{{ inventory_hostname }}" in the filepath can be used to set
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up random passwords per host (what simplifies password management in 'host_vars' variables).
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Generated passwords contain a random mix of upper and lowercase ASCII letters, the
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numbers 0-9 and punctuation (". , : - _"). The default length of a generated password is 30 characters.
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This length can be changed by passing an extra parameter::
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---
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- hosts: all
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tasks:
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# create a mysql user with a random password:
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- mysql_user: name={{ client }}
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password="{{ lookup('password', 'credentials/' + client + '/' + tier + '/' + role + '/mysqlpassword length=15') }}"
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priv={{ client }}_{{ tier }}_{{ role }}.*:ALL
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(...)
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More Lookups
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````````````
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.. note:: This feature is very infrequently used in Ansible. You may wish to skip this section.
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.. versionadded:: 0.8
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Various *lookup plugins* allow additional ways to iterate over data. In `playbooks_loops` you will learn
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how to use them to walk over collections of numerous types. However, they can also be used to pull in data
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from remote sources, such as shell commands or even key value stores. This section will cover lookup
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plugins in this capacity.
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Here are some examples::
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---
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- hosts: all
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tasks:
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- debug: msg="{{ lookup('env','HOME') }} is an environment variable"
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- debug: msg="{{ item }} is a line from the result of this command"
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with_lines:
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- cat /etc/motd
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- debug: msg="{{ lookup('pipe','date') }} is the raw result of running this command"
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- debug: msg="{{ lookup('redis_kv', 'redis://localhost:6379,somekey') }} is value in Redis for somekey"
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- debug: msg="{{ lookup('dnstxt', 'example.com') }} is a DNS TXT record for example.com"
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- debug: msg="{{ lookup('template', './some_template.j2') }} is a value from evaluation of this template"
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As an alternative you can also assign lookup plugins to variables or use them
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elsewhere. This macros are evaluated each time they are used in a task (or
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template)::
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vars:
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motd_value: "{{ lookup('file', '/etc/motd') }}"
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tasks:
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- debug: msg="motd value is {{ motd_value }}"
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