Igor Cicimov

Igor Cicimov

DevOps at Encompass

Ansible summary

12 minute read , Jun 27, 2014

Summary of Ansible features.

Configuration file

intro_configuration.html

First one found from of

  • Contents of $ANSIBLE_CONFIG
  • ./ansible.cfg
  • ~/.ansible.cfg
  • /etc/ansible/ansible.cfg

Configuration settings can be overridden by environment variables - see constants.py in the source tree for names.

Patterns

intro_patterns.html

Used on the ansible command line, or in playbooks.

  • all (or *)
  • hostname: foo.example.com
  • groupname: webservers
  • or: webservers:dbserver
  • exclude: webserver:!phoenix
  • intersection: webservers:&staging

Operators can be chained: webservers:dbservers:&staging:!phoenix

Patterns can include variable substitutions: ``, wildcards: *.example.com or 192.168.1.*, and regular expressions: ~(web|db).*\.example\.com

Inventory files

intro_inventory.html, intro_dynamic_inventory.html

‘INI-file’ structure, blocks define groups. Hosts allowed in more than one group. Non-standard SSH port can follow hostname separated by ‘:’ (but see also ansible_ssh_port below).

Hostname ranges: www[01:50].example.com, db-[a:f].example.com

Per-host variables: foo.example.com foo=bar baz=wibble

  • [foo:children]: new group foo containing all members if included groups
  • [foo:vars]: variable definitions for all members of group foo

Inventory file defaults to /etc/ansible/hosts. Veritable with -i or in the configuration file. The ‘file’ can also be a dynamic inventory script. If a directory, all contained files are processed.

Variable files:

intro_inventory.html

YAML; given inventory file at ./hosts:

  • ./group_vars/foo: variable definitions for all members of group foo
  • ./host_vars/foo.example.com: variable definitions for foo.example.com

group_vars and host_vars directories can also exist in the playbook directory. If both paths exist, variables in the playbook directory will be loaded second.

Behavioral inventory parameters:

intro_inventory.html

  • ansible_ssh_host
  • ansible_ssh_port
  • ansible_ssh_user
  • ansible_ssh_pass
  • ansible_sudo_pass
  • ansible_connection
  • ansible_ssh_private_key_file
  • ansible_python_interpreter
  • ansible_*_interpreter

Playbooks

playbooks_intro.html, playbooks_roles.html

Playbooks are a YAML list of one or more plays. Most (all?) keys are optional. Lines can be broken on space with continuation lines indented.

Playbooks consist of a list of one or more ‘plays’ and/or inclusions:

---
- include: playbook.yml
- <play>
- ...

Plays

playbooks_intro.html, playbooks_roles.html, playbooks_variables.html, playbooks_conditionals.html, playbooks_acceleration.html, playbooks_delegation.html, playbooks_prompts.html, playbooks_tags.html Forum posting Forum postinb

Plays consist of play metadata and a sequence of task and handler definitions, and roles.

    - hosts: webservers
      remote_user: root
      sudo: yes
      sudo_user: postgress
      su: yes
      su_user: exim
      gather_facts: no
      accelerate: no
      accelerate_port: 5099
      any_errors_fatal: yes
      max_fail_percentage: 30
      connection: local
      serial: 5
      vars:
        http_port: 80
      vars_files:
        - "vars.yml"
        - [ "try-first.yml", "try-second-.yml" ]
      vars_prompt:
        - name: "my_password2"
          prompt: "Enter password2"
          default: "secret"
          private: yes
          encrypt: "md5_crypt"
          confirm: yes
          salt: 1234
          salt_size: 8
      tags: 
        - stuff
        - nonsence
      pre_tasks:
        - <task>
        - ...
      roles:
        - common
        - { role: common, port: 5000, when: "bar == 'Baz'", tags :[one, two] }
        - { role: common, when: month == 'Jan' }
        - ...
      tasks:
        - include: tasks.yaml
        - include: tasks.yaml foo=bar baz=wibble
        - include: tasks.yaml
          vars:
            foo: aaa 
            baz:
              - z
              - y
        - { include: tasks.yaml, foo: zzz, baz: [a,b]}
        - include: tasks.yaml
          when: day == 'Thursday'
        - <task>
        - ...
      post_tasks:
        - <task>
        - ...
      handlers:
        - include: handlers.yml
        - <task>
        - ...

Using encrypt with vars_prompt requires that Passlib is installed.

In addition the source code implies the availability of the following which don’t seem to be mentioned in the documentation: name, user (deprecated), port, accelerate_ipv6, role_names, and vault_password.

Task definitions

playbooks_intro.html, playbooks_roles.html, playbooks_async.html, playbooks_checkmode.html, playbooks_delegation.html, playbooks_environment.html, playbooks_error_handling.html, playbooks_tags.html ansible-1-5-released Forum posting Ansible examples

Each task definition is a list of items, normally including at least a name and a module invocation:

    - name: task
      remote_user: apache
      sudo: yes
      sudo_user: postgress
      sudo_pass: wibble
      su: yes
      su_user: exim
      ignore_errors: True
      delegate_to: 127.0.0.1
      async: 45
      poll: 5
      always_run: no
      run_once: false
      meta: flush_handlers
      no_log: true
      environment: <hash>
      environment:
        var1: val1
        var2: val2
      tags: 
        - stuff
        - nonsence
      <module>: src=template.j2 dest=/etc/foo.conf
      action: <module>, src=template.j2 dest=/etc/foo.conf
      action: <module>
      args:
          src=template.j2
          dest=/etc/foo.conf
      local_action: <module> /usr/bin/take_out_of_pool 
      when: ansible_os_family == "Debian"
      register: result
      failed_when: "'FAILED' in result.stderr"
      changed_when: result.rc != 2
      notify:
        - restart apache

delegate_to: 127.0.0.1 is implied by local_action:

The forms <module>: <args>, action: <module> <args>, and local_action: <module> <args> are mutually-exclusive.

Additional keys when_*, until, retries and delay are documented below under ‘Loops’.

In addition the source code implies the availability of the following which don’t seem to be mentioned in the documentation: first_available_file (deprecated), transport, connection, any_errors_fatal.

Roles

playbooks_roles.html

Directory structure:

    playbook.yml
    roles/
       common/
         tasks/
           main.yml
         handlers/
           main.yml
         vars/
           main.yml
         meta/
           main.yml
         defaults/
           main.yml
         files/
         templates/
         library/

Modules

modules.htm, modules_by_category.html

List all installed modules with

    ansible-doc --list

Document a particular module with

    ansible-doc <module>

Show playbook snippet for specified module

    ansible-doc -i <module>

Variables

playbooks_roles.html, playbooks_variables.html

Names: letters, digits, underscores; starting with a letter.

Substitution examples:

  • {{ var }}
  • {{ var["key1"]["key2"]}}
  • {{ var.key1.key2 }}
  • {{ list[0] }}

YAML requires an item starting with a variable substitution to be quoted.

Sources:

  • Highest priority:
    • --extra-vars on the command line
  • General:
    • vars component of a playbook
    • From files referenced by vars_file in a playbook
    • From included files (incl. roles)
    • Parameters passed to includes
    • register: in tasks
  • Lower priority:
    • Inventory (set on host or group)
  • Lower priority:
    • Facts (see below)
    • Any /etc/ansible/facts.d/filename.fact on managed machines (sets variables with `ansible_local.filename. prefix)
  • Lowest priority
    • Role defaults (from defaults/main.yml)

Built-in:

  • hostvars (e.g. hostvars[other.example.com][...])
  • group_names (groups containing current host)
  • groups (all groups and hosts in the inventory)
  • inventory_hostname (current host as in inventory)
  • inventory_hostname_short (first component of inventory_hostname)
  • play_hosts (hostnames in scope for current play)
  • inventory_dir (location of the inventory)
  • inventoty_file (name of the inventory)

Facts:

Run ansible hostname -m setup, but in particular:

  • ansible_distribution
  • ansible_distribution_release
  • ansible_distribution_version
  • ansible_fqdn
  • ansible_hostname
  • ansible_os_family
  • ansible_pkg_mgr
  • ansible_default_ipv4.address
  • ansible_default_ipv6.address

Content of ‘registered’ variables:

playbooks_conditionals.html, playbooks_loops.html

Depends on module. Typically includes:

  • .rc
  • .stdout
  • .stdout_lines
  • .changed
  • .msg (following failure)
  • .results (when used in a loop)

See also failed, changed, etc filters.

When used in a loop the result element is a list containing all responses from the module.

Additionally available in templates:

  • ansible_managed: string containing the information below
  • template_host: node name of the template’s machine
  • template_uid: the owner
  • template_path: absolute path of the template
  • template_fullpath: the absolute path of the template
  • template_run_date: the date that the template was rendered

Filters

playbooks_variables.html

  • {{ var | to_nice_json }}
  • {{ var | to_json }}
  • {{ var | from_json }}
  • {{ var | to_nice_yml }}
  • {{ var | to_yml }}
  • {{ var | from_yml }}
  • {{ result | failed }}
  • {{ result | changed }}
  • {{ result | success }}
  • {{ result | skipped }}
  • {{ var | manditory }}
  • {{ var | default(5) }}
  • {{ list1 | unique }}
  • {{ list1 | union(list2) }}
  • {{ list1 | intersect(list2) }}
  • {{ list1 | difference(list2) }}
  • {{ list1 | symmetric_difference(list2) }}
  • {{ ver1 | version_compare(ver2, operator='>=', strict=True }}
  • {{ list | random }}
  • {{ number | random }}
  • {{ number | random(start=1, step=10) }}
  • {{ list | join(" ") }}
  • {{ path | basename }}
  • {{ path | dirname }}
  • {{ path | expanduser }}
  • {{ path | realpath }}
  • {{ var | b64decode }}
  • {{ var | b64encode }}
  • {{ filename | md5 }}
  • {{ var | bool }}
  • {{ var | int }}
  • {{ var | quote }}
  • {{ var | md5 }}
  • {{ var | fileglob }}
  • {{ var | match }}
  • {{ var | search }}
  • {{ var | regex }}
  • {{ var | regexp_replace('from', 'to' )}}

See also default jinja2 filters. In YAML, values starting { must be quoted.

Lookups

playbooks_lookups.html

Lookups are evaluated on the control machine.

  • {{ lookup('file', '/etc/foo.txt') }}
  • {{ lookup('password', '/tmp/passwordfile length=20 chars=ascii_letters,digits') }}
  • {{ lookup('env','HOME') }}
  • {{ lookup('pipe','date') }}
  • {{ lookup('redis_kv', 'redis://localhost:6379,somekey') }}
  • {{ lookup('dnstxt', 'example.com') }}
  • {{ lookup('template', './some_template.j2') }}

Lookups can be assigned to variables and will be evaluated each time the variable is used.

Lookup plugins also support loop iteration (see below).

Conditions

playbooks_conditionals.html

when: <condition>, where condition is:

  • var == "Vaue", var >= 5, etc.
  • var, where var coreces to boolean (yes, true, True, TRUE)
  • var is defined, var is not defined
  • <condition1> and <condition2> (also or?)

Combined with with_items, the when statement is processed for each item.

when can also be applied to includes and roles. Conditional Imports and variable substitution in file and template names can avoid the need for explicit conditionals.

Loops

playbooks_loops.html

In addition the source code implies the availability of the following which don’t seem to be mentioned in the documentation: csvfile, etcd, inventory_hostname.

Standard:

    - user: name= state=present groups=wheel
      with_items:
        - testuser1
        - testuser2
       
    - name: add several users
      user: name= state=present groups=
      with_items:
        - { name: 'testuser1', groups: 'wheel' }
        - { name: 'testuser2', groups: 'root' }

      with_items: somelist

Nested:

    - mysql_user: name= priv=.*:ALL                
                               append_privs=yes password=foo
      with_nested:
        - [ 'alice', 'bob', 'eve' ]
        - [ 'clientdb', 'employeedb', 'providerdb' ]

Over hashes:

Given

    ---
    users:
      alice:
        name: Alice Appleworth
        telephone: 123-456-7890
      bob:
        name: Bob Bananarama
        telephone: 987-654-3210
        
    tasks:
      - name: Print phone records
        debug: msg="User  is  
                         ()"
        with_dict: users

Fileglob:

    - copy: src= dest=/etc/fooapp/ owner=root mode=600
      with_fileglob:
        - /playbooks/files/fooapp/*

In a role, relative paths resolve relative to the roles/<rolename>/files directory.

With content of file:

(see example for authorized_key module)

    - authorized_key: user=deploy key=""
      with_file:
        - public_keys/doe-jane
        - public_keys/doe-john

See also the file lookup when the content of a file is needed.

Parallel sets of data:

Given

    ---
    alpha: [ 'a', 'b', 'c', 'd' ]
    numbers:  [ 1, 2, 3, 4 ]
    
    - debug: msg="{{ item.0 }} and {{ item.1 }}"
      with_together:
        - alpha
        - numbers

Subelements:

Given

    ---
    users:
      - name: alice
        authorized:
          - /tmp/alice/onekey.pub
          - /tmp/alice/twokey.pub
      - name: bob
        authorized:
          - /tmp/bob/id_rsa.pub
    
    - authorized_key: "user={{ item.0.name }} key='{{ lookup('file', item.1) }}'"
      with_subelements:
         - users
         - authorized

Integer sequence:

Decimal, hexadecimal (0x3f8) or octal (0600)

    - user: name= state=present groups=evens
      with_sequence: start=0 end=32 format=testuser%02x
          
      with_sequence: start=4 end=16 stride=2
          
      with_sequence: count=4

Random choice:

    - debug: msg=
      with_random_choice:
         - "go through the door"
         - "drink from the goblet"
         - "press the red button"
         - "do nothing"

Do-Until:

    - action: shell /usr/bin/foo
      register: result
      until: result.stdout.find("all systems go") != -1
      retries: 5
      delay: 10

Results of a local program:

    - name: Example of looping over a command result
      shell: /usr/bin/frobnicate 
      with_lines: /usr/bin/frobnications_per_host 
                           --param

To loop over the results of a remote program, use register: result and then with_items: result.stdout_lines in a subsequent task.

Indexed list:

    - name: indexed loop demo
      debug: msg="at array position {{ item.0 }} there is a value {{ item.1 }}"
      with_indexed_items: some_list

Flattened list:

    ---
    # file: roles/foo/vars/main.yml
    packages_base:
      - [ 'foo-package', 'bar-package' ]
    packages_apps:
      - [ ['one-package', 'two-package' ]]
      - [ ['red-package'], ['blue-package']]
      
    - name: flattened loop demo
      yum: name= state=installed
      with_flattened:
        - packages_base
        - packages_apps

First found:

    - name: template a file
      template: src= dest=/etc/myapp/foo.conf
      with_first_found:
        - files:
            - .conf
            - default.conf
          paths:
             - search_location_one/somedir/
             - /opt/other_location/somedir/

Tags

Both plays and tasks support a tags: attribute.

    - template: src=templates/src.j2 dest=/etc/foo.conf
      tags:
        - configuration

Tags can be applied to roles and includes (effectively tagging all included tasks)

    roles:
        - { role: webserver, port: 5000, tags: [ 'web', 'foo' ] }

    - include: foo.yml tags=web,foo

To select by tag:

    ansible-playbook example.yml --tags "configuration,packages"
    ansible-playbook example.yml --skip-tags "notification"

Command lines

ansible

Usage: ansible <host-pattern> [options]

Options:
  -a MODULE_ARGS, --args=MODULE_ARGS
                        module arguments
  -k, --ask-pass        ask for SSH password
  --ask-su-pass         ask for su password
  -K, --ask-sudo-pass   ask for sudo password
  --ask-vault-pass      ask for vault password
  -B SECONDS, --background=SECONDS
                        run asynchronously, failing after X seconds
                        (default=N/A)
  -C, --check           don't make any changes; instead, try to predict some
                        of the changes that may occur
  -c CONNECTION, --connection=CONNECTION
                        connection type to use (default=smart)
  -f FORKS, --forks=FORKS
                        specify number of parallel processes to use
                        (default=5)
  -h, --help            show this help message and exit
  -i INVENTORY, --inventory-file=INVENTORY
                        specify inventory host file
                        (default=/etc/ansible/hosts)
  -l SUBSET, --limit=SUBSET
                        further limit selected hosts to an additional pattern
  --list-hosts          outputs a list of matching hosts; does not execute
                        anything else
  -m MODULE_NAME, --module-name=MODULE_NAME
                        module name to execute (default=command)
  -M MODULE_PATH, --module-path=MODULE_PATH
                        specify path(s) to module library
                        (default=/usr/share/ansible)
  -o, --one-line        condense output
  -P POLL_INTERVAL, --poll=POLL_INTERVAL
                        set the poll interval if using -B (default=15)
  --private-key=PRIVATE_KEY_FILE
                        use this file to authenticate the connection
  -S, --su              run operations with su
  -R SU_USER, --su-user=SU_USER
                        run operations with su as this user (default=root)
  -s, --sudo            run operations with sudo (nopasswd)
  -U SUDO_USER, --sudo-user=SUDO_USER
                        desired sudo user (default=root)
  -T TIMEOUT, --timeout=TIMEOUT
                        override the SSH timeout in seconds (default=10)
  -t TREE, --tree=TREE  log output to this directory
  -u REMOTE_USER, --user=REMOTE_USER
                        connect as this user (default=jw35)
  --vault-password-file=VAULT_PASSWORD_FILE
                        vault password file
  -v, --verbose         verbose mode (-vvv for more, -vvvv to enable
                        connection debugging)
  --version             show program's version number and exit

ansible-playbook

Usage: ansible-playbook playbook.yml

Options:
  -k, --ask-pass        ask for SSH password
  --ask-su-pass         ask for su password
  -K, --ask-sudo-pass   ask for sudo password
  --ask-vault-pass      ask for vault password
  -C, --check           don't make any changes; instead, try to predict some
                        of the changes that may occur
  -c CONNECTION, --connection=CONNECTION
                        connection type to use (default=smart)
  -D, --diff            when changing (small) files and templates, show the
                        differences in those files; works great with --check
  -e EXTRA_VARS, --extra-vars=EXTRA_VARS
                        set additional variables as key=value or YAML/JSON
  -f FORKS, --forks=FORKS
                        specify number of parallel processes to use
                        (default=5)
  -h, --help            show this help message and exit
  -i INVENTORY, --inventory-file=INVENTORY
                        specify inventory host file
                        (default=/etc/ansible/hosts)
  -l SUBSET, --limit=SUBSET
                        further limit selected hosts to an additional pattern
  --list-hosts          outputs a list of matching hosts; does not execute
                        anything else
  --list-tasks          list all tasks that would be executed
  -M MODULE_PATH, --module-path=MODULE_PATH
                        specify path(s) to module library
                        (default=/usr/share/ansible)
  --private-key=PRIVATE_KEY_FILE
                        use this file to authenticate the connection
  --skip-tags=SKIP_TAGS
                        only run plays and tasks whose tags do not match these
                        values
  --start-at-task=START_AT
                        start the playbook at the task matching this name
  --step                one-step-at-a-time: confirm each task before running
  -S, --su              run operations with su
  -R SU_USER, --su-user=SU_USER
                        run operations with su as this user (default=root)
  -s, --sudo            run operations with sudo (nopasswd)
  -U SUDO_USER, --sudo-user=SUDO_USER
                        desired sudo user (default=root)
  --syntax-check        perform a syntax check on the playbook, but do not
                        execute it
  -t TAGS, --tags=TAGS  only run plays and tasks tagged with these values
  -T TIMEOUT, --timeout=TIMEOUT
                        override the SSH timeout in seconds (default=10)
  -u REMOTE_USER, --user=REMOTE_USER
                        connect as this user (default=jw35)
  --vault-password-file=VAULT_PASSWORD_FILE
                        vault password file
  -v, --verbose         verbose mode (-vvv for more, -vvvv to enable
                        connection debugging)
  --version             show program's version number and exit

ansible-vault

playbooks_vault.html

Usage: ansible-vault [create|decrypt|edit|encrypt|rekey] [--help] [options] file_name

Options:
  -h, --help  show this help message and exit

See 'ansible-vault <command> --help' for more information on a specific command.

ansible-doc

Usage: ansible-doc [options] [module...]

Show Ansible module documentation

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -M MODULE_PATH, --module-path=MODULE_PATH
                             Ansible modules/ directory
  -l, --list            List available modules
  -s, --snippet         Show playbook snippet for specified module(s)
  -v                    Show version number and exit

ansible-galaxy

Usage: ansible-galaxy [init|info|install|list|remove] [--help] [options] ...

Options:
  -h, --help  show this help message and exit

  See 'ansible-galaxy <command> --help' for more information on a
  specific command

ansible-pull

Usage: ansible-pull [options] [playbook.yml]

ansible-pull: error: URL for repository not specified, use -h for help

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