Not for the faint of heart - a detailed explanation of the usage of roles in ansible-playbook (II)

preamble

In this article, we'll continue to cover the various uses of roles in ansible-playbook.

environmental preparation

assemblies	releases
operating system	Ubuntu 22.04.4 LTS
ansible	2.17.6

basic usage

file structure

.
├── 
├── 
└── roles
    └── base
        └── tasks
            └── 

Defining global public variables

Add a new group_vars directory and add new files

.
├── 
├── 
├── group_vars
│   └── 
└── roles
    └── base
        └── tasks
            └── 

▶ cat group_vars/
info: IT paiqiu

▶ cat roles/base/tasks/
- name: first
  debug:
    msg: "hello world {{ info }}"

Running:

▶ ansible-playbook -i  

...
TASK [base : first] **********************************************************************************************
ok: [10.22.11.166] => {
    "msg": "hello world IT paiqiu"
}
...

Defining role-level variables

Can override global variables

In the rolebase The following is a new vars directory and a new file

.
├── 
├── 
├── group_vars
│   └── 
└── roles
    └── base
        ├── tasks
        │   └── 
        └── vars
            └── 

▶ cat roles/base/tasks/
- name: first
  debug:
    msg: "hello world {{ info }}"

▶ cat roles/base/vars/
info:
  name: wilson
  addr: cd

Running:

▶ ansible-playbook -i  

...
TASK [base : first] **********************************************************************************************
ok: [10.22.11.166] => {
    "msg": "hello world {'name': 'wilson', 'addr': 'cd'}"
}
...

Define the static file directory

This is equivalent to defining the root directory at the role level to better manage files that need to be transferred in the rolebaseCreate a directory belowfilesand in thefilesBelow is the file to be transferred

.
├── 
├── 
├── group_vars
│   └── 
└── roles
    └── base
        ├── files
        │   └── 
        ├── tasks
        │   └── 
        └── vars
            └── 

transportTo target machine

- name: first
  copy: src= dest=/tmp/

The default is to go back to roles/base/files, so you don't need to add a path in front of it.

The copy module automatically checks the md5 of the file to be transferred, and if it hasn't changed, then it won't be transferred anymore

Defining a template

Each time a file is transferred it is re-rendered through the input variables before transferring it, in the rolebaseCreate a directory belowtemplatesand create a file

.
├── 
├── 
├── group_vars
│   └── 
└── roles
    └── base
        ├── files
        │   └── 
        ├── tasks
        │   └── 
        ├── templates
        │   └── 
        └── vars
            └── 

There are two variables defined in the template file, a manually set variable called version and the ansible built-in variable called inventory_hostname.

▶ cat roles/base/templates/
{{ version }}
{{ inventory_hostname }}

▶ cat roles/base/tasks/
- name: first
  template: src= dest=/tmp/ mode=0644

Running:

▶ ansible-playbook -i  -e version=2 

PLAY [deploy] ****************************************************************************************************

TASK [base : first] **********************************************************************************************
changed: [10.22.11.166]

PLAY RECAP *******************************************************************************************************
10.22.11.166               : ok=1    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Log in to the target machine to view it:

▶ cat 
2
10.22.11.166

2is the variable passed in for this task.10.22.11.166is the ip address of the target machine

Defining event-driven

Usually used for actions that need to be triggered after certain tasks have been completed, e.g., restarting a service after publishing a configuration file. In the rolebaseCreate a directory underhandlersand create a file

.
├── 
├── 
├── group_vars
│   └── 
└── roles
    └── base
        ├── files
        │   └── 
        ├── handlers
        │   └── 
        ├── tasks
        │   └── 
        ├── templates
        │   └── 
        └── vars
            └── 

Creating Eventsfirst handler

▶ cat roles/base/handlers/
- name: first handler
  debug:
    msg: echo 'hello world'

▶ cat roles/base/tasks/
- name: first
  template: src= dest=/tmp/ mode=0644
  notify: first handler

Running:

▶ ansible-playbook -i  -e version=2 

PLAY [deploy] ****************************************************************************************************

TASK [base : first] **********************************************************************************************
changed: [10.22.11.166]

RUNNING HANDLER [base : first handler] ***************************************************************************
ok: [10.22.11.166] => {
    "msg": "echo 'hello world'"
}

PLAY RECAP *******************************************************************************************************
10.22.11.166               : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Similarly, if the event precursor doesn't happen, then the event notification won't happen, for example, if the event precursor is the transfer of a file, and if the file doesn't change, it won't be transferred again, then the event won't happen again either

Add more tasks

Currently onlyIn addition, a task dedicated to the transfer of files is being added.

▶ cat roles/base/tasks/
- name: main
  include_tasks: 
  vars:
    app_version: 0.2

▶ cat roles/base/tasks/
- name: first
  debug:
    msg: "version: {{ app_version }}"

Running:

▶ ansible-playbook -i  

PLAY [deploy] ****************************************************************************************************

TASK [base : main] ***********************************************************************************************
included: /home/wilson/workspace/ansible/roles/base/tasks/ for 10.22.11.166

TASK [base : first] **********************************************************************************************
ok: [10.22.11.166] => {
    "msg": "version: 0.2"
}

PLAY RECAP *******************************************************************************************************
10.22.11.166               : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

If there are too many files, they can be handled by looping:

- name: main
  include_tasks: "{{ yaml_items }}"
  loop:
    - 
    - 
  loop_control:
    loop_var: yaml_items
  vars:
    app_version: 0.2

To add a few common commands

execute a commandshell

- name: display
  shell: echo 'hello world'

Transmission of documentscopy

The copy module automatically checks the md5 of the file to be transferred, and if it hasn't changed, then it won't be transferred anymore

- name: copy file
  copy: src= dest=/tmp/

Modify the contents of the document (one line)lineinfile

• path: Specify the path of the file to be operated (required)
• line: defines the complete line to be inserted or replaced (optional)
• regexp: Regular expression to match existing lines. Used in conjunction with line, matching lines will be replaced with
• state:
  • present (default): Ensures that the specified line exists.
  • absent: remove matching rows
• create: Whether to create the file if it does not exist (default yes)
• insertafter: specifies the location of the insertion line (default EOF)
  • EOF: End of File
  • BOF: Beginning of File
  • Regular expression: inserts after matching line
    insertbefore: similar to insertafter, but inserted before the matching line

Modify the current line after matching the line with a regular

- name: modify
  lineinfile: dest=/tmp/ regexp='^DC' line="DC=hello" state=present

Modify file contents (multiple lines/blocks)blockinfile

• path: Specify the path of the file to be manipulated (required)
• block: defines the content of the text to be inserted (required)
• marker: Specify the start and end strings of the marker block, default is # {mark} ANSIBLE MANAGED BLOCK
• state:
  • present (default): ensures that the block exists
  • absent: remove block
• create: Whether to create the file if it does not exist (default yes)
• insertafter: specifies the location of the insertion block (default EOF)
  • Available values:
    • EOF: End of File
    • BOF: Beginning of File
    • Regular expression: insert after matching line
• insertbefore: Similar to insertafter, but inserts before the matching line.

1) Add new content below a line and mark the added content

- name: add new content with markers
  blockinfile:
    path: /tmp/
    marker: "# {mark} by wilson"
    insertafter: '^DC'
    block: |
      name: wilson
      city: cd

View the results after running

▶ cat /tmp/
DC=hello
# BEGIN by wilson
name: wilson
city: cd
# END by wilson

2) Delete marked content

- name: Remove the managed block
  blockinfile:
    marker: "# {mark} by wilson"
    path: /tmp/
    state: absent

Adding blocks of content and marking them up makes it easy to modify and delete them.

Using templates

- name: hostname config
  template: src=etc/hostname dest=/etc/hostname

Setting File Permissionsfile

- name: change file 755
  file:
    path: /tmp/
    owner: wilson
    group: wilson
    state: file
    mode: 755

Using loopswith_items

with_items

Modify permissions for multiple directories

- name: change directory 755
  file:
    path: '{{  }}'
    owner: wilson
    group: wilson
    state: directory
    mode: '{{  }}'
  with_items:
    - { dir: '/tmp/1', mode: '0755'}
    - { dir: '/tmp/2', mode: '0755'}

loop

surelywith_items replace withloopIt's possible.

- name: change directory 755
  file:
    path: '{{  }}'
    owner: wilson
    group: wilson
    state: directory
    mode: '{{  }}'
  with_items:
    - { dir: '/tmp/1', mode: '0755'}
    - { dir: '/tmp/2', mode: '0755'}

nested loopwith_nested

Output each combination, equivalent to the Cartesian product

- name: nested loop
  debug:
    msg: "{{ item[0] }} {{ item[1] }}"
  with_nested:
    - [ "hello1", "hello2"]
    - [ "world1", "world2"]

Output results:

TASK [base : nested loop] ****************************************************************************************
ok: [127.0.0.1] => (item=['hello1', 'world1']) => {
    "msg": "hello1 world1"
}
ok: [127.0.0.1] => (item=['hello1', 'world2']) => {
    "msg": "hello1 world2"
}
ok: [127.0.0.1] => (item=['hello2', 'world1']) => {
    "msg": "hello2 world1"
}
ok: [127.0.0.1] => (item=['hello2', 'world2']) => {
    "msg": "hello2 world2"
}

File Content Loopwith_file

Printing the contents of a file line by line

- name: display file content
  debug:
    msg: "{{ item }}"
  with_file:
    - /tmp/

idempotence (math.)

When using roles to manage multiple devices, scripts should always be written with idempotency in mind, i.e., each execution should be guaranteed to produce the same result.

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