Bootstrapping Ansible on Fedora 23

Thu 15 October 2015 by Lars Kellogg-Stedman Tags ansible fedora

If you've tried running Ansible against a Fedora 23 system, you may have run into the following problem:

fatal: [myserver]: FAILED! => {"changed": false, "failed": true,
"msg": "/bin/sh: /usr/bin/python: No such file or directory\r\n",
"parsed": false}

Fedora has recently made the switch to only including Python 3 on the base system (at least for the cloud variant), while Ansible still requires Python 2. With Fedora 23, Python 3 is available as /usr/bin/python3, and /usr/bin/python is only available if you have installed the Python 2 interpreter.

This is not an insurmountable problem; Ansible's raw module can be used to run arbitrary commands on a remote host without requiring an installed Python interpreter. This gives us everything we need to bootstrap the remote environment.

The simplest playbook might look something like:

- hosts: all
  tasks:
    - name: install packages for ansible support
      raw: dnf -y -e0 -d0 install python python-dnf

(The python-dnf package is required if you want to install packages using the dnf module.)

So you drop this into a playbook and run it and...it still fails, with the same error. This is because Ansible will, by default, attempt to gather facts from the remote host by running the setup module, which requires Python. So we modify our playbook to look like this:

- hosts: all
  gather_facts: false
  tasks:
    - name: install packages for ansible support
      raw: dnf -y -e0 -d0 install python python-dnf

Setting gather_facts: false inhibits this initial fact collection; with this change, the playbook should run successfully:

$ ansible-playbook playbook.yml
PLAY ***************************************************************************

TASK [install packages for ansible support] ************************************
ok: [myserver -> localhost]

PLAY RECAP *********************************************************************
myserver                   : ok=1    changed=0    unreachable=0    failed=0

Having installed the basics, you can now use many of the standard Ansible modules:

- hosts: all
  gather_facts: true
  tasks:
    - lineinefile:
        dest: /etc/hosts
        line: "{{ansible_eth0.ipv4.address}} {{inventory_hostname}}"
        regexp: "{{inventory_hostname}}"
    - package:
        name: git
        state: present

As the above example demonstrates, now that the necessary Python stack is installed on the remote Fedora 23 host, Ansible is is able to gather facts about the host that can be used in tasks, templates, etc.

Note that with the raw module I had to use the dnf command explicitly, while in the above playbook I can use the package module for package installation, which relies on available facts to determine the correct package module.


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