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# Ansible-Boilerplate |
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[Ansible](https://www.ansible.com/) is a configuration management tool, similar to [Chef](https://www.chef.io/) and [Puppet](https://puppet.com/). It allows for performing logical configuration of infrastructure components, such as servers and network switches. The configuration files in this repository can act as a template for your own Ansible projects, in order to get you started quickly. Once you've customized the configuration files then new servers can be configured quickly — excluding their network configuration. This means that adding new servers is as simple as: |
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- Base OS installation of new server |
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- Network configuration of new server (including bond, bridge, DNS and routing) |
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- Configuration of password-less (public key) SSH authentication from the Ansible host (your laptop) to the new server |
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The remaining configuration (installing packages, configuring services, etc.) can then be achieved using Ansible. In addition, Ansible ensures that configuration of all servers is and remains consistent. |
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## Using this repository |
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Simply download (clone) the repository and start modifying files according to your needs. |
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``` |
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git clone https://github.com/acch/ansible-boilerplate.git myAnsibleProject/ |
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``` |
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Ideally, you'll want to use [Git](https://git-scm.com/) to manage your Ansible configuration files. For that purpose simply [fork](https://help.github.com/articles/fork-a-repo/) this repository into your own Git repository before cloning and customizing it. Git will allow you to version and roll-back changes with ease. |
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Specifically, you'll want to customize the following files: |
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- Add your own hosts and groups to file `hosts`. You'll want to replace `[anygroup]` with a more meaningful group name, and add your own groups as required. |
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- Define roles by adding subdirectories underneath directory `roles/`. You'll want to rename `anyrole/` to a more meaningful role name, and add your own roles as required. |
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- Associate your hosts (groups) with your roles by adding appropriate playbooks in the root directory. Rename `anygroup.yml` to a more meaningful playbook name. |
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- Import all your playbooks in the main `site.yml` playbook. |
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## Using Ansible |
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Install `ansible` on your laptop and link the `hosts` file from `/etc/ansible/hosts` to the file in your repository. Now you're all set. |
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To run a single (ad-hoc) task on multiple servers: |
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``` |
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# Check connectivity |
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ansible all -m ping -u root |
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# Run single command on all servers |
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ansible all -m command -a "cat /etc/hosts" -u root |
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# Run single command only on servers in specific group |
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ansible anygroup -m command -a "cat /etc/hosts" -u root |
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# Run single command on individual server |
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ansible server1 -m command -a "cat /etc/hosts" -u root |
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``` |
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As the `command` module is the default, it can also be omitted: |
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``` |
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ansible server1 -a "cat /etc/hosts" -u root |
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``` |
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To use shell variables on the remote server, use the `shell` module instead of `command`, and use single quotes for the argument: |
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``` |
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ansible server1 -m shell -a 'echo $HOSTNAME' -u root |
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``` |
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The true power of ansible comes with so called *playbooks* — think of them as scripts, but they're declarative. Playbooks allow for running multiple tasks on any number of servers, as defined in the configuration files (`*.yml`): |
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``` |
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# Run all tasks on all servers |
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ansible-playbook site.yml -v |
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# Run all tasks only on group of servers |
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ansible-playbook anygroup.yml -v |
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# Run all tasks only on individual server |
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ansible-playbook site.yml -v -l server1 |
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``` |
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Note that `-v` produces verbose output. `-vv` and `-vvv` are also available for even more (debug) output. |
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To verify what tasks would do without changing the actual configuration, use the `--list-hosts` and `--check` parameters: |
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``` |
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# Show hosts that would be affected by playbook |
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ansible-playbook site.yml --list-hosts |
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# Perform dry-run to see what tasks would do |
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ansible-playbook site.yml -v --check |
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``` |
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Running all tasks in a playbook may take a long time. *Tags* are available to organize tasks so one can only run specific tasks to configure a certain component: |
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``` |
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# Show list of available tags |
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ansible-playbook site.yml --list-tags |
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# Only run tasks required to configure DNS |
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ansible-playbook site.yml -v -t dns |
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``` |
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Note that the above command requires you to have tasks defined with the `tags: dns` attribute. |
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## Configuration files |
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The `hosts` file defines all hosts and groups which they belong to. Note that a single host can be member of multiple groups. Define groups for each rack, for each network, or for each environment (e.g. production vs. test). |
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### Playbooks |
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Playbooks associate hosts (groups) with roles. Define a separate playbook for each of your groups, and then import all playbooks in the main `site.yml` playbook. |
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File | Description |
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---- | ----------- |
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`site.yml` | Main playbook - runs all tasks on all servers |
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`anygroup.yml` | Group playbook - runs all tasks on servers in group *anygroup* |
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### Roles |
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The group playbooks (e.g. `anygroup.yml`) simply associate hosts with roles. Actual tasks are defined in these roles: |
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``` |
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roles/ |
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├── common/ Applied to all servers |
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│ ├── handlers/ |
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│ ├── tasks/ |
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│ │ └ main.yml Tasks for all servers |
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│ └── templates/ |
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└── anyrole/ Applied to servers in specific group(s) |
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├── handlers/ |
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├── tasks/ |
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│ └ main.yml Tasks for specific group(s) |
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└── templates/ |
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``` |
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Consider adding separate roles for different applications (e.g. webservers, dbservers, hypervisors, etc.), or for different responsibilities which servers fulfill (e.g. infra_server vs. infra_client). |
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### Tags |
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Use the following command to show a list of available tags: |
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``` |
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ansible-playbook site.yml --list-tags |
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``` |
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Consider adding tags for individual components (e.g. DNS, NTP, HTTP, etc.). |
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Role | Tags |
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--- | --- |
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Common | all,check |