# Update nodes /etc/hosts file from a master file **URL:** \ **Category:** Ansible Project\ **Created:** [April 28, 2019, 9:39am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207 "2019-04-28T09:39:07Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![ecrosby](https://avatars.discourse-cdn.com/v4/letter/e/8edcca/32.png) [@ecrosby](https://forum.ansible.com/u/ecrosby)\ **Post date:** [April 28, 2019, 9:39am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/1 "2019-04-28T09:39:07Z")
I hope I am posting this to the correct area… I’m really new to Ansible and am in the process of trying to learn it. Question: Does Ansible have the ability to look at a master file that contains host file information and deploy information from that master file to the /etc/hosts file on all the nodes in my environment so that when I add a new host all that I need to do is update that master file and redeploy to all my nodes appending, or replacing, that existing /etc/hosts file? Thanks. ---
**Author:** ![Kunalsing\_Thakur](https://avatars.discourse-cdn.com/v4/letter/k/3d9bf3/32.png) [@Kunalsing\_Thakur](https://forum.ansible.com/u/Kunalsing_Thakur)\ **Post date:** [April 28, 2019, 9:42am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/2 "2019-04-28T09:42:44Z")
If I understand correctly the master file you are talking about is playbook term in ansible. The playbook has all information related to hosts and deployment instruction. You can give the Input in playbook and it will modify the stuff accordingly. ---
**Author:** ![ecrosby](https://avatars.discourse-cdn.com/v4/letter/e/8edcca/32.png) [@ecrosby](https://forum.ansible.com/u/ecrosby)\ **Post date:** [April 28, 2019, 9:46am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/3 "2019-04-28T09:46:17Z")
Actually, I am referring to the master file outside the playbook. In other words I just have a plain text master file with all my host entries. Then, I create a playbook that references that master file to send to all nodes as reference to update their /etc/hosts file. Is that possible? ---
**Author:** ![Kunalsing\_Thakur](https://avatars.discourse-cdn.com/v4/letter/k/3d9bf3/32.png) [@Kunalsing\_Thakur](https://forum.ansible.com/u/Kunalsing_Thakur)\ **Post date:** [April 28, 2019, 9:53am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/4 "2019-04-28T09:53:14Z")
Yes. Use copy module. I hope so you are referring to inventory file which has all node details. Like below /etc/ansible/inventory [all] host1 host2 host3 /etc/ansible/playbook/master host entry files /etc/ansible/playbook/test.yaml host: all tasks: - name: copying host file to all nodes copy: src: /etc/ansible/playbook/master dest: /etc/hosts mode: 0755 ---
**Author:** ![ecrosby](https://avatars.discourse-cdn.com/v4/letter/e/8edcca/32.png) [@ecrosby](https://forum.ansible.com/u/ecrosby)\ **Post date:** [April 29, 2019, 8:57am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/5 "2019-04-29T08:57:56Z")
No, I’m not referring to the inventory file, it will be a separate file that will have other hosts. However, you have pointed me in the right direction, thank you for that. Here is what I have come up with and this works, but my problem now is that every time there are new servers added, the existing servers will get the same hosts records all the time so there will be duplicates in the /etc/hosts. I haven’t been able to figure out how to look at the existing servers in the host file and only add new servers.: _— # Copy hosts file_ _- hosts: all_ _become: yes_ _tasks:_ _- name: update hosts template file_ _copy:_ _src: /home/ansible/hostfile_ _dest: /tmp/hostfile_ _owner: root_ _group: root_ _mode: 0644_ _backup: yes_ _- name: Append template file to master host file_ _shell: cat /tmp/hostfile \>\> /etc/hosts_ _- name: Delete temp file_ _file:_ _path: /tmp/hostfile_ _state: absent_ This works, but my problem now is that every time there are new servers added, the existing servers will get the same hosts records all the time so there will be duplicates in the /etc/hosts. I haven’t been able to figure out how to look at the existing servers in the host file and only add new servers. ---
**Author:** ![Kunalsing\_Thakur](https://avatars.discourse-cdn.com/v4/letter/k/3d9bf3/32.png) [@Kunalsing\_Thakur](https://forum.ansible.com/u/Kunalsing_Thakur)\ **Post date:** [April 29, 2019, 9:07am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/6 "2019-04-29T09:07:31Z")
Why do you need that to append. If you have hosts file you can use copy to replace that role in every hosts file. I assume you have DNS server ---
**Author:** ![ecrosby](https://avatars.discourse-cdn.com/v4/letter/e/8edcca/32.png) [@ecrosby](https://forum.ansible.com/u/ecrosby)\ **Post date:** [April 29, 2019, 9:30am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/7 "2019-04-29T09:30:12Z")
I do not have a DNS server, hence the need to manually update the /etc/hosts file. This a small network with less than 50 clients. ---
**Author:** ![Kunalsing\_Thakur](https://avatars.discourse-cdn.com/v4/letter/k/3d9bf3/32.png) [@Kunalsing\_Thakur](https://forum.ansible.com/u/Kunalsing_Thakur)\ **Post date:** [April 29, 2019, 9:38am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/8 "2019-04-29T09:38:09Z")
Can you show me one example of your hosts file from one of node ---
**Author:** ![Jonathan\_Lozada\_De\_L](https://avatars.discourse-cdn.com/v4/letter/j/eb8c5e/32.png) [@Jonathan\_Lozada\_De\_L](https://forum.ansible.com/u/Jonathan_Lozada_De_L)\ **Post date:** [April 29, 2019, 10:37am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/9 "2019-04-29T10:37:23Z")
Hello, I think you should use templating and jinja2 a bit in here. Will make the file easier to control and avoid appending. You can also use NetworkManager (if you use that). ---
**Author:** ![ecrosby](https://avatars.discourse-cdn.com/v4/letter/e/8edcca/32.png) [@ecrosby](https://forum.ansible.com/u/ecrosby)\ **Post date:** [April 30, 2019, 7:40am UTC](https://forum.ansible.com/t/update-nodes-etc-hosts-file-from-a-master-file/30207/10 "2019-04-30T07:40:14Z")
I think I found a way to do what I want to do. It’s dirty but it works: _— # Copy hosts file_ _- hosts: all_ _become: yes_ _tasks:_ _- name: update hosts template file_ _copy:_ _src: /home/ansible/hostfile_ _dest: /tmp/hostfile_ _owner: root_ _group: root_ _mode: 0644_ _backup: yes_ _- name: create master template file_ _shell: diff /tmp/hostfile /etc/hosts | grep '\< ’ | sed ‘s/\< //’ \> /tmp/masterhosts_ _- name: Append template file to master host file_ _shell: cat /tmp/masterhosts \>\> /etc/hosts_ _- name: Delete temp file_ _file:_ _path: /tmp/hostfile_ _state: absent_ _- name: Delete master temp file_ _file:_ _path: /tmp/masterhosts_ _state: absent_