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Michele Cereda 074baa33c7 Fixed templating examples in ansible's notes

2022-05-02 20:29:19 +02:00

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Ansible

# Install.
pip3 install --user ansible && port install sshpass   # darwin
sudo pamac install ansible sshpass                    # manjaro linux

# Show hosts' ansible facts.
ansible -i hostfile -m setup all
ansible -i host1,hostn, -m setup host1 -u remote-user
ansible -i localhost, -c local -km setup localhost

# Check the syntax of a playbook.
# This will *not* execute the plays inside it.
ansible-playbook path/to/playbook.yml --syntax-check

# Execute a playbook.
ansible-playbook path/to/playbook.yml -i hosts.list
ansible-playbook path/to/playbook.yml -i host1,host2,hostn, -l hosts,list
ansible-playbook path/to/playbook.yml -i host1,host2,other, -l hosts-pattern

# Show what changes (with details) a play whould apply to the local machine.
ansible-playbook path/to/playbook.yml -i localhost, -c local -vvC

# Only execute tasks with specific tags.
ansible-playbook path/to/playbook.yml --tags "configuration,packages"

# Avoid executing tasks with specific tags.
ansible-playbook path/to/playbook.yml --skip-tags "system,user"

# Check what tasks will be executed.
ansible-playbook example.yml --list-tasks
ansible-playbook example.yml --list-tasks --tags "configuration,packages"
ansible-playbook example.yml --list-tasks --skip-tags "system,user"

# List roles installed from Galaxy.
ansible-galaxy list

# Install roles from Galaxy.
ansible-galaxy install namespace.role
ansible-galaxy install --roles-path ~/ansible-roles namespace.role
ansible-galaxy install namespace.role,v1.0.0
ansible-galaxy install git+https://github.com/namespace/role.git,commit-hash
ansible-galaxy install -r requirements.yml

# Remove roles installed from Galaxy.
ansible-galaxy remove namespace.role

Templating

- name: >-
    Remove empty or false values from a list piping it to 'select()'.
    Returns ["string"] from ["", "string", 0, false].
  vars:
    list: ["", "string", 0, false]
  debug:
    var: list | select

- name: >-
    Remove only empty strings from a list 'reject()'ing them.
    Returns ["string", 0, false] from ["", "string", 0, false].
  vars:
    list: ["", "string", 0, false]
  debug:
    var: list | reject('match', '^$')

- name: >-
    Merge two lists.
    Returns ["a", "b", "c", "d"] from ["a", "b"] and ["c", "d"].
  vars:
    list1: ["a", "b"]
    list2: ["c", "d"]
  debug:
    var: list1 + list2

- name: >-
    Dedupe elements in a list.
    Returns ["a", "b"] from ["a", "b", "b", "a"].
  vars:
    list: ["a", "b", "b", "a"]
  debug:
    var: list | unique

- name: >-
    Sort list by version number (not lexicographically).
    Returns ['2.7.0', '2.8.0', '2.9.0',, '2.10.0' '2.11.0'] from ['2.8.0', '2.11.0', '2.7.0', '2.10.0', '2.9.0']
  vars:
    list: ['2.8.0', '2.11.0', '2.7.0', '2.10.0', '2.9.0']
  debug:
    var: list | community.general.version_sort

- name: >-
    Compare a semver version number.
    Returns a boolean result.
  debug:
    var: "'2.0.0-rc.1+build.123' is version('2.1.0-rc.2+build.423', 'ge', version_type='semver')"

- name: >-
    Generate a random password.
    Returns a random string following the specifications.
  vars:
    password: "{{ lookup('password', '/dev/null length=32 chars=ascii_letters,digits,punctuation') }}"
  debug:
    var: password

- name: >-
    Hash a password.
    Returns a hash of the requested type.
  vars:
    password: abcd
    salt: "{{ lookup('community.general.random_string', special=false) }}"
  debug:
    var: password | password_hash('sha512', salt)

Roles

Get roles

Roles can be either created:

ansible-galaxy init role-name

or installed from Ansible Galaxy:

---
# requirements.yml
collections:
  - community.docker

ansible-galaxy install mcereda.boinc_client
ansible-galaxy install --roles-path ~/ansible-roles namespace.role
ansible-galaxy install namespace.role,v1.0.0
ansible-galaxy install git+https://github.com/namespace/role.git,0b7cd353c0250e87a26e0499e59e7fd265cc2f25
ansible-galaxy install -r requirements.yml

Role dependencies

---
# role/meta/main.yml
dependencies:
  - role: common
    vars:
      some_parameter: 3
  - role: postgres
    vars:
      dbname: blarg
      other_parameter: 12

Output formatting

Introduced in Ansible 2.5

Change Ansible's output setting the stdout callback to json or yaml:

ANSIBLE_STDOUT_CALLBACK=yaml

# ansible.cfg
[defaults]
stdout_callback = json

yaml will set tasks output only to be in the defined format:

$ ANSIBLE_STDOUT_CALLBACK=yaml ansible-playbook --inventory=localhost.localdomain, ansible/localhost.configure.yml -vv --check
PLAY [Configure localhost] *******************************************************************

TASK [Upgrade system packages] ***************************************************************
task path: /home/user/localhost.configure.yml:7
ok: [localhost.localdomain] => changed=false
  cmd:
  - /usr/bin/zypper
  - --quiet
  - --non-interactive
  …
  update_cache: false

The json output format will be a single, long JSON file:

$ ANSIBLE_STDOUT_CALLBACK=yaml ansible-playbook --inventory=localhost.localdomain, ansible/localhost.configure.yml -vv --check
{
    "custom_stats": {},
    "global_custom_stats": {},
    "plays": [
        {
            "play": {
                …
                "name": "Configure localhost"
            },
            "tasks": [
                {
                    "hosts": {
                        "localhost.localdomain": {
                            …
                            "action": "community.general.zypper",
                            "changed": false,
                            …
                            "update_cache": false
                        }
                    }
                    …
…
}

Troubleshooting

Print all known variables

Print the special variable vars as a task:

- name: Debug all variables
  debug: var=vars

Force notified handlers to run at a specific point

Use the meta plugin with the flush_handlers option:

- name: Force all notified handlers to run at this point, not waiting for normal sync points
  meta: flush_handlers

Run specific tasks even in check mode

Add the check_mode: false pair to the task:

- name: this task will make changes to the system even in check mode
  check_mode: false
  command: /something/to/run --even-in-check-mode

Dry-run only specific tasks

Add the check_mode: true pair to the task:

- name: This task will always run under checkmode and not change the system
  check_mode: true
  lineinfile:
    line: "important file"
    dest: /path/to/file.conf
    state: present

Set up recursive permissions on a directory so that directories are set to 755 and files to 644

Use the special X mode setting in the file plugin:

- name: Fix files and directories' permissions
  file:
    dest: /path/to/some/dir
    mode: u=rwX,g=rX,o=rX
    recurse: yes

Only run a task when another changed or failed

When a task executes, it also stores the two special values changed and failed in its results. You can use those as conditions to execute the next ones:

- name: Trigger task
  ansible.builtin.command: any
  register: trigger_result
  ignore_errors: true

- name: Run if changed
  when: trigger_result.changed
  debug: msg="The trigger task changed"

- name: Run if failed
  when: trigger_result.failed
  debug: msg="The trigger task failed"

Define when a task changed or failed

This lets you avoid using ignore_errors.

Use the changed_when and failed_when attributes to define your own conditions:

- name: Task with custom results
  ansible.builtin.command: any
  register: result
  changed_when:
    - result.rc == 2
    - result.stderr | regex_search('things changed')
  failed_when:
    - result.rc != 0
    - not (result.stderr | regex_search('all good'))

Set environment variables for a play, role or task

Environment variables can be set at a play, block, or task level using the environment keyword:

- name: Use environment variables for a task
  environment:
    HTTP_PROXY: http://example.proxy
  ansible.builtin.command: curl ifconfig.io

The environment keyword does not affect Ansible itself or its configuration settings, the environment for other users, or the execution of other plugins like lookups and filters; variables set with environment do not automatically become Ansible facts, even when set at the play level.

Set variables to the value of environment variables

Use the lookup() plugin with the env option:

- name: Use a local environment variable
  debug: msg="HOME={{ lookup('env', 'HOME') }}"

Check if a list contains an item and fail otherwise

- name: Check if a list contains an item and fail otherwise
  when: item not in list
  fail: msg="item not in list"

11 KiB

Raw Blame History

Ansible

Templating

Roles

Get roles

Role dependencies

Output formatting

Troubleshooting

Print all known variables

Force notified handlers to run at a specific point

Run specific tasks even in check mode

Dry-run only specific tasks

Set up recursive permissions on a directory so that directories are set to 755 and files to 644

Only run a task when another changed or failed

Define when a task changed or failed

Set environment variables for a play, role or task

Set variables to the value of environment variables

Check if a list contains an item and fail otherwise

Further readings

Sources

11 KiB Raw Blame History

Ansible

Templating

Roles

Get roles

Role dependencies

Output formatting

Troubleshooting

Print all known variables

Force notified handlers to run at a specific point

Run specific tasks even in check mode

Dry-run only specific tasks

Set up recursive permissions on a directory so that directories are set to 755 and files to 644

Only run a task when another changed or failed

Define when a task changed or failed

Set environment variables for a play, role or task

Set variables to the value of environment variables

Check if a list contains an item and fail otherwise

Further readings

Sources

11 KiB

Raw Blame History