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+++ date = "2016-08-17T13:14:16+02:00" title = "Ansible" toc = true weight = 25 +++

Although it can be rather tricky to master, Ansible is probably the most important tool when working with the UTN servers. All applications have been set up in such a way, that most server related tasks are done using Ansible. By using Ansible, the systems become easily reproducible, and there is a form of automatic documentation for the steps taken to launch a system.

Setting up UTN Ansible

The UTN Ansible files are located in a repository on GitHub. Once you've installed Ansible, on your local machine, and cloned the repository, you have to take the following steps:

  • Create a file called password.txt, that contains the vault password (handed over from one system administrator to the next).
  • In the folder host_vars, create a file for each of the servers, named according to the FQDN of the server (e.g.,, containing your sudo password for that host.

You should now be able to run all playbooks in the repository using ansible-playbook [playbook].

{{% notice tip %}}

If you are getting an error saying ansible is being run in a world writable directory, you need to change the permissions on the ansible folder. Go to your ansible directory cd /path/to/ansible and execute chmod 775 ..

{{% /notice %}}

A Quick Introduction

Ansible is a deployment system. It helps automating the deployment of various tasks while managing a server pool. Ansible repositories are rather rationally split up into several parts:

  • Playbooks are collections of tasks working to a common goal (for the deployment) of an application. These files can be seen as recipes. These files are also the main part of the repositories, these files will be run, using the other files as resources.
  • Roles are collections of tasks that will most likely be used in various playbooks. Each role has a similar folder structure to the main Ansible repository; this means that a role can be self-contained in the resources it needs.
  • Handlers are tasks that can be invoked when a tasks actually changes something. These are usually reload or restart tasks. Handlers are stored at the bottom of a playbook, tasks file, or in the handlers directory.
  • Variables are located in among others the vars and host_vars directories. The use of variables can help to avoid making duplicate playbooks/roles.
  • Templates are files that have interleaved variables, these can be used to easily use the same file for multiple deployments. These files are located in the templates
  • Regular files used are located in the files directory.

The Vault

Some variables are encrypted with the use of ansible-vault such as the passwords. This makes it possible to share the repository publicly without sharing the passwords. To edit the contents use ansible-vault edit path/to/file.yml. You can also simply view the contents by switching edit with view.

UTN Playbooks

These are the playbooks that currently exist within the unions ansible repository.

  • common.yml - Meant to execute initial server configuration (e.g., manage users, add firewall).
  • custom_web.yml - Deploys the applications specified in vars/custom_installations.yml to turing.
  • custom_web_babbage.yml - Deploys the applications specified in vars/custom_installations_babbage.yml to babbage. These applications aren't made with drupal so they need to be in their own playbook.
  • documentation.yml - Gets the latest version from the documentation github repo and updates the documentation on this website.
  • drupal7.yml - Deploys all drupal 7 applications specifies in vars/drupal7_installations.yml to babbage.
  • moore.yml - Updates moore to the latest version on the master branch in the moore github repo.
  • survey.yml - Deploys limesurvey to turing.
  • upgrade.yml - Playbook to run apt-get update & apt-get distupgrade on all servers.
  • webserver.yml - Installs and configures extra requirements for the webservers (e.g., install a mail server).

{{% notice tip %}}

When running playbooks that operate on multiple servers you have to use ssh-add to save your passphrase so you don't have to supply it manually. If you can't run ssh-add try running eval $(ssh-agent -s).

{{% /notice %}}

Managing users and logins

Currently the logins are managed using the logins role in Ansible. Most management is done in the vars/users.yml file, which contains all variables used by the role to determine which user has an account on which server.

Most accounts are shared by a committee, these account have the name of the (abbreviation of the) committee. However, management at UTN, like the system administrator, get their own personal account.

Access to shared accounts is managed using the SSH keys, these keys are stored in files/pubkeys and have the name of the account. To give someone access to the account, add their public key on a new line in the file. This means that multiple people can have access to the same account. To take away their access, remove the line in the file containing their public key.

When a committee or section switches to a new group of people, a new public key must be made for that person. This is because only those who should have access shold have access. When you get a new key from the new person make sure to remove the public key of the old person.

Add a user

To add an account create a new entry in vars/users by copying another user and changing the parameters.

Remove a user

To remove an account add the account name to the old_users variable and remove it from the user variable.

Apply changes

After changes to the variables have been made, the common.yml playbook can be executed to perform the changes.

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