How to use a loop in a file template to the target host with Ansible?
This is extremely useful for service configuration files, placeholder web pages, reports, and so much more use cases. I’m going to show you a live Playbook with some simple Ansible code. I’m Luca Berton and welcome to today’s episode of Ansible Pilot.
Ansible loop in file template
- ansible.builtin.template
- Template a file out to a target host
- ansible_managed, template_host, template_uid, template_path, template_fullpath, template_destpath, and template_run_date
Today we’re talking about the Ansible module template.
The full name is ansible.builtin.template, it’s part of ansible-core and is included in all Ansible installations.
It templates a file out to a target host. Templates are processed by the Jinja2 templating language.
Also you could use also some special variables in your templates: ansible_managed, template_host, template_uid, template_path, template_fullpath, template_destpath, and template_run_date.
It supports a large variety of Operating Systems.
For basic text formatting, use the Ansible ansible.builtin.copy module or for empty file Ansible ansible.builtin.file module.
For Windows, use the ansible.windows.win_template module instead.
Parameters
- src path - template (“templates/” dir)
- dest path - target location
- validate string - validation command before ("%s")
- backup boolean - no/yes
- mode/owner/group - permission
- setype/seuser/selevel - SELinux
Let me highlight the most useful parameters for the template module. The only required parameters are “src” and “dest”. The “src” parameter specifies the template file name. Templates usually are stored under “templates” directories with “.j2” file extension. The “dest” parameter specifies the path where to render the template to on the remote machine. The “validate” parameters allow you to specify the validation command to run before copying it into place. It’s very useful with configuration files for services. Please note that the special escape sequence “%s” is going to be expanded by Ansible with the destination path. If the “backup” parameter is enabled Ansible creates a backup file including the timestamp information before copying it to the destination. Let me also highlight that we could also specify the permissions and SELinux properties.
Playbook
Loop in file template with Ansible Playbook. You could find more information about Magic Variables: https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html
code
- generate_myhosts.yml
---
- name: template module Playbook
hosts: all
become: true
tasks:
- name: generate /etc/myhosts file
ansible.builtin.template:
src: templates/hosts.j2
dest: /etc/myhosts
owner: root
group: root
mode: '0644'
- hosts.j2
# {{ ansible_managed }}
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
{% for host in group['all'] %}
{{ hostvars[host]['ansible_host'] }} {{ hostvars[host]['inventory_hostname'] }} {{ hostvars[host]['inventory_hostname_short'] }}
{% endfor %}
execution
$ ansible-playbook -i apply\ template/inventory apply\ template/generate_myhosts.yml
PLAY [template module Playbook] ***********************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [generate /etc/myhosts file] *****************************************************************
changed: [demo.example.com]
PLAY RECAP ****************************************************************************************
demo.example.com : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
before execution
$ ssh [email protected]
Last login: Tue Nov 23 17:10:30 2021 from 192.168.0.101
[devops@demo ~]$ sudo su
[root@demo devops]# ls -al /etc/myhosts
ls: cannot access '/etc/myhosts': No such file or directory
[root@demo devops]#
after execution
$ ssh [email protected]
Last login: Tue Nov 23 17:32:39 2021 from 192.168.0.101
[devops@demo ~]$ sudo su
[root@demo devops]# ls -al /etc/myhosts
-rw-r--r--. 1 root root 214 Nov 23 17:32 /etc/myhosts
[root@demo devops]# cat /etc/myhosts
# Ansible managed
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.0.190 demo.example.com demo
[devops@demo ~]$ exit
logout
Connection to demo.example.com closed.
ansible-pilot $ cat apply\ template/inventory
demo.example.com ansible_host=192.168.0.190
[all:vars]
ansible_connection=ssh
ansible_user=devops
Conclusion
Now you know how to use a for loop in a Jinja2 template file with Magic Variables with Ansible. Subscribe to the YouTube channel, Medium, and Website, X (formerly Twitter) to not miss the next episode of the Ansible Pilot.
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