Ansible - Mass Management

October 23, 2021 13:02

Master

Install

sudo apt install ansible

Done.

A word of warning beforehand: Try to use your local Ansible setup and NOT the global files like the one under /etc/ansible/hosts. This is just to prevent you from running everything with root 24/7!

Create an ansible ssh-key

Create the key with ssh-keygen (running from your home directory and therefore set the path to .ssh/ansible). Edit ~/.ansible.cfg and set private_key_file to the path from before.

You install the key by using (NEVER EVER install this key into your root user, for security reasons):

ssh-copy-id -i ~/.ssh/ansible [TARGET_USER]@[TARGET_HOST]

Then test it with:

ssh ~/.ssh/ansible [TARGET_USER]@[TARGET_HOST]

And you can always use the jump-host configuration as shown below:

ssh-copy-id -i ~/.ssh/ansible -o ProxyCommand="ssh -i ~/.ssh/ansible -W %h:%p [JUMP_USER]@[JUMP_HOST]" [TARGET_USER]@[TARGET_HOST]
ssh ~/.ssh/ansible -o ProxyCommand="ssh -i ~/.ssh/ansible -W %h:%p [JUMP_USER]@[JUMP_HOST]" [TARGET_USER]@[TARGET_HOST]

Why not use -J for the JumpHost configuration? This option is new and does not inherit any further parameters from the parent process (like -i). It can be really useful in other scenarios, but not for Ansible (right now).

Setup your users inventory

Add this to your .bashrc (only if you wish to use a local inventory):

export ANSIBLE_INVENTORY=$HOME/ansible/hosts

Now create the hosts file as following…

Register hosts

Edit ~/ansible/hosts (take a note at the excellent documentation in /etc/ansible/hosts and there) and…

  • add some hosts (at the top):
    foo.example.com
    bar.example.com
    
  • define a new group of hosts:
    [servergroupname]
    one.example.com
    two.example.com
    
  • define a ip variable for a specific host:
    three.example.com ansible_host=[HOST_IP]
    
  • define a username & key variable for a specific host:
    four.example.com ansible_user=[USER] ansible_ssh_private_key_file=/some/other/ssh/key
    
  • define a ssh-jump variable for a specific host (the ProxyCommand will be executed as the ansible user -> make sure the ansible user can access his own key, also you may omit the StrictHostKeyChecking later on):
    five.example.com ansible_ssh_common_args='-o StrictHostKeyChecking=no -o ProxyCommand="ssh -i ~/.ssh/ansible -W %h:%p -q [JUMP_HOST_USER]@[JUMP_HOST_URL]"'
    
  • define any variable for a specific host group:
    [servergroupname:vars]
    ansible_user=[USER]
    ansible_ssh_private_key_file=/some/other/ssh/key
    
  • define any variable for any host (this one variable is needed for newer installations, as the classic /bin/python path won’t work anymore!):
    [all:vars]
    ansible_python_interpreter=/usr/bin/python3
    

Test your connections

ansible all -m ping

You’ll may need to use sudo, if the key was created inside the configuration directory. Instead of all you could also use any other configured group name like servergroupname from before.

Running arbitrary commands

ansible all -a "uname -a"

Running arbitrary commands, but not everywhere

ansible 'all:!somegroup' -a "uname -a"

As root with password

ansible all -a "uname -a" --become --ask-become-pass

Define a Playbook

Create a new playbook.yml and fill it (I would recommend to create it under ~/ansible/playbooks):

---
- name: Playbook Demo
  hosts: all
  become: false

  tasks:
  - name: Receive hostnames
    command: hostname
  - name: Show uname
    command: uname -a
    register: out
  - debug: var=out.stdout_lines

The debug task will show the output variable - meaning the output of the module command.

Run it:

ansible-playbook playbook.yaml

Install & remove some SSH keys

---
- name: SSH Key Demo
  hosts: all

  tasks:
  - name: Make sure the ansible key is there
    authorized_key:
      user: "{{ ansible_user }}"
      state: present
      key: "{{ lookup('file', '/etc/ansible/ssh_key.pub') }}"
  - name: Remove an untrusted (old) key
    authorized_key:
      user: "{{ ansible_user }}"
      state: absent
      key: "ssh-rsa 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 [email protected]"

The authorized_key-module - what is that?! When you are unsure what Ansible can do for you - try the documentation.

Install some applications

---
- name: APT Demo
  hosts: all
  become: true

  tasks:
  - name: Install THE BEST console text editor
    apt:
      name: nano
      state: present

Make sure to run this one with --ask-become-pass, as apt can only be used as root!

Replay a stuck playbook

Just run (the .retry file will be automatically created):

ansible-playbook playbook.yml --limit @playbook.retry

The automatic way

import os
import re
import glob
import logging
import argparse
import subprocess

"""
Run this by using crontab - should be silent if everything is unreachable, otherwise it will show outputs!
Example need? Try that:
*/10 * * * * cd $HOME/ansible && python3 ./autoretry.py
...also ensure that crontab is sending you the commands output as e.g. email!
"""

parser = argparse.ArgumentParser()
parser.add_argument('-d', '--debug', action='store_true', help='Show debug msgs')
if parser.parse_args().debug:
    logging.basicConfig(level=logging.DEBUG)
else:
    logging.basicConfig(level=logging.INFO)

logger = logging.getLogger(__name__)
files = glob.glob('./**/*.retry', recursive=True)
for playbookRetry in files:
    # Setup vars
    playbookPath = os.path.split(playbookRetry)
    playbookExt = os.path.splitext(playbookPath[1])
    playbookYml = os.path.join(playbookPath[0], playbookExt[0] + '.yml')
    logger.debug(playbookPath[0])
    logger.debug(playbookYml)
    logger.debug(playbookRetry)

    # Execute the playbook
    if not os.path.isfile(playbookYml):
        logger.warning('Playbook src for retry not found!')
        continue
    try:
        # Yes, subprocess is bad - but the ansible python api is the worst. This works. Even using different versions. The api? Not.
        res = subprocess.run(['ansible-playbook', playbookYml, '--limit', '@' + os.path.join(playbookPath[0], playbookExt[0] + '.retry')],
            capture_output=True, cwd=os.getcwd(), timeout=60*60*2) # Timeout after 2 hours
    except subprocess.TimeoutExpired:
        logger.error('2h timeout on command execution')
        continue

    # Check if anything was successful or if we completed all
    lines = res.stdout.decode().split('\n')
    doneSmth = False
    unreachSmth = False
    for l in lines:
        if re.match(r'.+:.+ok=.+changed=.+unreachable=0.+failed=.+', l):
            doneSmth = True
        if re.match(r'.+:.+ok=.+changed=.+unreachable=1.+failed=.+', l):
            unreachSmth = True

    # Show logs on success or failures
    for l in lines:
        l = l.strip()
        if len(l) == 0:
            continue
        if doneSmth:
            logger.info(l)
        else:
            logger.debug(l)
    # ...else: Done nothing. Try again later...
    logger.debug('doneSmth ' + str(doneSmth))
    logger.debug('unreachSmth ' + str(unreachSmth))

    if not unreachSmth:
        logger.info('All plays finished. Removing retry file!')
        os.remove(playbookRetry)

Enjoy.