Ansible (OBSOLETE)

Owned by Former user (Deleted)
Last updated: Oct 18, 2022 by Eddie Rubeiz
4 min read

We use Ansible to build and configure our servers.

Our Ansible configuration is stored at https://github.com/sciencehistory/ansible.

Overview of the codebase

The information in the Ansible repository is organized into four main file types: the hosts file, a set of playbooks, roles called by each playbook, and encrypted variables files.

Hosts file (hosts)

This is a catalog of our Ansible-managed servers. Each server is associated with information about its purpose (tags) and instructions about how to contact it (ip addresses and hostnames). The file is organized by category; each category contains zero or more server IP's associated with it. These are:

  • "Tier" categories:
    • prod: production servers.
    • stage: staging servers.
  • "Role" categories:

Playbooks

These are the main tasks Ansible knows how to perform:

  • build_ami.yml : Create an Amazon machine image, which serves as a template for the actual EC2 cloud servers. To list tasks:
    • ansible-playbook --list-tasks --extra-vars "hosts=stage" --extra-vars "role=solr tier=stage" build_ami.yml
  • create_ec2.yml: Create a new server based on an AMI. To list tasks:
    • ansible-playbook --list-tasks --extra-vars "hosts=stage" update-box.yml
    • ansible-playbook --list-tasks --extra-vars "hosts=prod" update-box.yml
  • resize.yml: Stop a server, resize its disks, and then restart it.
  • sync.yml: Copy over data from production to staging. To list tasks:
    • ansible-playbook --list-tasks sync.yml
  • update-box.yml: Runs updates on a server.

Roles


These are the subtasks of the playbooks (for instance, the recipe for installing Apache on a given server). They are listed in roles/*/tasks/main.yml files. The roles can also refer to:

  • Subsidiary tasks, known as handlers: roles/*/handlers/main.yml
  • Templates, typically for configuration files. These are roles/*/templates/* and are often stored as Jinja templates. (see http://jinja.pocoo.org/). For instance, the roles/apache/tasks/main.yml role has a choice of three Apache configuration files in roles/apache/templates/, which it uses depending on which server it's configuring.

Variables files

The values of the variables are used by the roles in building and modifying the servers. These are in group_vars/* and there is one for each category listed in the Hosts files. In certain cases, when a server belongs to two categories (e.g. it's both prod and solr), a special override file is used: e.g. group_vars/solr is overridden by group_vars/solr_prod_override .

The variables in these files describe specific features of each server, such as:

  • "Switches" that describe in more detail what software needs to be installed on the server. For instance, ansible-inventory/group_vars/jobs sets switch "fedora" to false but "sufia" to true; these switches are used by the roles to run or skip various parts of the installation.
  • A listing of each volume that needs to be created and mounted on the server, along with details such as size, mount point, and filesystem type.
  • Details associated with specific softare: versions, usernames, passwords, versions, port numbers and so on.

Variables files are the only ones encrypted.

The password for ansible-vault is in

Shared/P/Support/Computer Services/Digital Collections/ansible-vault.txt

To view a file:

ansible-vault --vault-password-file FILE_CONTAINING_PASSWORD view ENCRYPTED_FILE

To search the files for a particular string:

ls -1 ansible-inventory/group_vars | while read N ; do echo $N: ; \
ansible-vault --vault-password-file FILE_CONTAINING_PASSWORD \
view ansible-inventory/group_vars/$N | grep -i STRING_TO_LOOK_FOR ; done

Building a new machine on AWS with Ansible

Note: ansible-vault password and all current AWS keys are in shared network drive  Othmer Library\Digital Collections - Internal Access\Authentication - Confidential
If you do not have access, you will need to be added to the allowed group.

This assumes you have the main Ansible password inside a plain Ascii file at /your/ansible_password.txt .

  1. Check ansible variables in the encrypted file
    1. $ ansible-vault edit --vault-password-file /your/ansible_password.txt group_vars/all
  2. run the ansible playbook
    1. $ ansible-playbook create_ec2.yml --ask-vault-pass --private-key=/PATH/TO/KEY --extra-vars "role=ROLE tier=SERVICE_LEVEL" --extra-vars "@group_vars/ROLE_SERVICE_LEVEL_override"
      1. Use chf_prod.pem for all production level machines
      2. Use test.pem for all other machines
      3. Select the role and service level of the machine you want to build.
    2. OR, if you're re-running scripts on an existing machine: 
      1. $ ansible-playbook -i hosts my_playbook.yml --ask-vault-pass [-e hosts=target]
        1. target can be one of the groups in the hosts file: staging, production, dev, ec2hosts
  3. Assign an elastic IP to the new box if if needs one
  4. Consider naming the aws volumes for 'root' and 'data' – this isn't done in the scripts (but probably could be!)
  5. Set up to use capistrano (below) or just deploy with capistrano (above)
  6. Run configure_prod.yml if on production to set up e-mail password resets, ssl, and backup procedures.

Creating a test box using Ansible

Scenario: You've changed the Ansible scripts that affect the build process for the jobs server. To make sure everything looks right, you want to spin up a new jobs2-stage on EC2 without disturbing the functioning of jobs1-stage.

Procedure:

Make sure the main Ansible password is available inside a plain text file at, e.g.,  /your/ansible_password.txt .

Change the "iteration" so your box has a different label from the existing jobs1-stage. (Use whichever editor you want, but some work better than others.)

EDITOR=emacs ansible-vault edit --vault-password-file /your/ansible_password.txt . group_vars/all

Find the line that mentions "iteration" and set it to an unused number.

iteration: 2

This will result in your new jobs box being labeled jobs2-stage.

List the tasks you'll be performing. This is helpful to make sure everything looks good before actually running the script.

ansible-playbook --vault-password-file /your/ansible_password.txt --list-tasks --extra-vars "role=jobs tier=stage" create_ec2.yml

Now actually create the box:

ansible-playbook --vault-password-file /your/ansible_password.txt --extra-vars "role=jobs tier=stage" create_ec2.yml

Note: this will modify your "hosts" file in the root directory of ansible-inventory by adding the new box's IP address to it.

In the EC2 dashboard, you'll see a new EC2 instance called jobs2-stage. You can log into it as you would any ec2 server.

Watch the progress of the ansible-playbook command in your terminal.

When you're done, you can get rid of the box in the EC2 console (but don't get rid of the wrong box!) by selecting it, then choosing Actions > Instance State > Terminate.

New AWS Key

  1. Generate a new ssh key on AWS (EC2 > Keypairs)
    1. place it in ~/.ssh
    2. chmod 0600.
    3. useful command if you're having problems with the key: $ openssl rsa -in chf_prod.pem -check