Update nodes /etc/hosts file from a master file

[ecr...@gmail.com]

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.

[Kunalsing Thakur]

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.

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[ecr...@gmail.com]

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?

On Sunday, April 28, 2019 at 5:43:06 AM UTC-4, Kunalsing Thakur wrote:

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.

On Sun, 28 Apr 2019, 15:09 <ecr...@gmail.com wrote:

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.

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[Kunalsing Thakur]

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

       

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[ecr...@gmail.com]

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.

[Kunalsing Thakur]

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

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[ecr...@gmail.com]

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.

[Kunalsing Thakur]

Can you show me one example of your hosts file from one of node

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[Jonathan Lozada De La Matta]

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).

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--

Jonathan lozada de la matta

AUTOMATION PRACTICE

 

[ecr...@gmail.com]

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

On Monday, April 29, 2019 at 6:37:45 AM UTC-4, Jonathan Lozada De La Matta wrote:

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).

To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/a00f8ca8-cb4d-477a-a6a5-770bcfc6e939%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

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