Iterate host definitions into single file

[Chris Jefferies]

I use ansible a lot for work and for my home lab.  I love it.

I keep needing an approach that so far has stumped me, so asking here for advice.

I want to create a single file (an icinga2_hosts.conf) which has a separate collection of attributes from each host in my hosts inventory file.  I would like to use jinja2 to template one instance and iterate through the hosts building the file in one go; not host by host in the usual ansible approach...  although if a single file can be built by that method, I'm all ears. 

I think I could duplicate the hosts section in the vars section and then iterate the yaml data for the single file with a loop.

I could actually create a file for each host and that would actually work in icinga2.  But I want it in a single file for future readability and to avoid having to look in each host file for some anomaly.

I could give up on ansible for this and use python and jinja2 to pass the hosts inventory file to a jinja2 render function.

Is there a way to actually read the hosts inventory in traditional ansible style and iterate it into a single file using jinja2 as the template mechanism?

I've wanted to do this in other scenarios but abandoned those attempts.

Any tips and tricks appreciated.

Chris.

[Dick Visser]

On Thu, 9 Dec 2021 at 08:20, Chris Jefferies <chr...@gmail.com> wrote:

I use ansible a lot for work and for my home lab.  I love it.

I keep needing an approach that so far has stumped me, so asking here for advice.

I want to create a single file (an icinga2_hosts.conf) which has a separate collection of attributes from each host in my hosts inventory file. 

What do you mean by this?

Can you give an example?

I would like to use jinja2 to template one instance and iterate through the hosts building the file in one go; not host by host in the usual ansible approach...  although if a single file can be built by that method, I'm all ears. 

I think I could duplicate the hosts section in the vars section and then iterate the yaml data for the single file with a loop.

I could actually create a file for each host and that would actually work in icinga2.  But I want it in a single file for future readability and to avoid having to look in each host file for some anomaly.

I could give up on ansible for this and use python and jinja2 to pass the hosts inventory file to a jinja2 render function.

Is there a way to actually read the hosts inventory in traditional ansible style and iterate it into a single file using jinja2 as the template mechanism?

I've wanted to do this in other scenarios but abandoned those attempts.

Any tips and tricks appreciated.

Chris.

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[Stefan Hornburg (Racke)]

On 09/12/2021 08:19, Chris Jefferies wrote:
> I use ansible a lot for work and for my home lab.  I love it.
>
> I keep needing an approach that so far has stumped me, so asking here for advice.
>
> I want to create a single file (an icinga2_hosts.conf) which has a separate collection of attributes from each host in my hosts inventory file.  I would like to use jinja2 to template one instance and iterate through the hosts building the file in one go; not host by host in the usual ansible approach...  although if a single file can be built by that method, I'm all ears.
>

You can iterate through your hosts with

{% for host in ansible_play_hosts %}
...
{% endfor %}

and use hostvars[host]['myattribute'] to access an attribute from you inventory.

To create the file, use template or copy with content parameter and add

run_once: yes
delegate_to: localhost

Regards
Racke

> I think I could duplicate the hosts section in the vars section and then iterate the yaml data for the single file with a loop.
>
> I could actually create a file for each host and that would actually work in icinga2.  But I want it in a single file for future readability and to avoid having to look in each host file for some anomaly.
>
> I could give up on ansible for this and use python and jinja2 to pass the hosts inventory file to a jinja2 render function.
>
> Is there a way to actually read the hosts inventory in traditional ansible style and iterate it into a single file using jinja2 as the template mechanism?
>
> I've wanted to do this in other scenarios but abandoned those attempts.
>
> Any tips and tricks appreciated.
> Chris.
>

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Ecommerce and Linux consulting + Perl and web application programming.
Debian and Sympa administration.

[Chris Jefferies]

Racke,

ansible_play_hosts - I did not know about this magic variable, as they call it.  I'll test but I assume that the attributes come with it.

Then you describe defining a task with:

run_once: yes
delegate_to: localhost

I see run_once in the documentation and they said it was like running only on the first host; which is fine because now I want to run using ansible_play_hosts which gets me all the hosts.

Then instead of using:

delegate_to: localhost

I think I can delegate to the server I am actually running against:

delegate_to: icinga.example.com

Or are you suggesting I delegate to localhost, then copy the resulting file?

dick,

I hope the above result explains what and how I would like to do.  But to explain a bit... I want to end up with a file that has something like this content, below.  I was trying to figure out a way to subvert the normal processing of an inventory host file and do it all into one file.  Racke has show a way of doing this by using a "magic variable" that holds all of the host info I need and how to run it only once so I don't get a bunch of repetitive files being generated.  It's beautiful...  if it works.  ;)   I'm sure it will.

object Host "myhost1.mine.me" {
  import "generic-host"
  address = "192.68.0.1"
  vars.os = "Linux"
}

object Host "myhost2.mine.me" {
  import "generic-host"
  address = "192.68.0.2"
  vars.os = "Linux"
}

Thank you.

[Stefan Hornburg (Racke)]

On 09/12/2021 10:07, Chris Jefferies wrote:
> Racke,
> *ansible_play_hosts* - I did not know about this *magic* variable, as they call it.  I'll test but I assume that the attributes come with it.

>
> Then you describe defining a task with:
>
> run_once: yes
> delegate_to: localhost
>

> I see run_once in the documentation and they said it was like running only on the first host; which is fine because now I want to run using *ansible_play_hosts* which gets me all the hosts.

>
> Then instead of using:
> delegate_to: localhost
>
> I think I can delegate to the server I am actually running against:
> delegate_to: icinga.example.com

Chris,

yes you can use icinga.example.com if that host is part of your inventory.

Racke

> > To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com> <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com?utm_medium=email&utm_source=footer <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com?utm_medium=email&utm_source=footer>>.

>
>
> --
> Ecommerce and Linux consulting + Perl and web application programming.
> Debian and Sympa administration.
>
>

> --
> You received this message because you are subscribed to the Google Groups "Ansible Project" group.
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[Chris Jefferies]

Racke,

One glitch that I did not understand...  

I must add:

host: all

instead of just 

hosts: icinga.example.com

... and run with all hosts defined in the playbook.  I was only using icinga.example.com (the false name of my server).  Now I must add:

when: "{{inventory_hostname == 'icinga.example.com'}}"

to the other tasks.  Small price to pay.

Thank you.

[Stefan Hornburg (Racke)]

On 09/12/2021 11:36, Chris Jefferies wrote:
> Racke,
> One glitch that I did not understand...
>
> I must add:
>
> host: all
>
> instead of just
>
> hosts: icinga.example.com
>
> ... and run with all hosts defined in the playbook.  I was only using icinga.example.com (the false name of my server).  Now I must add:
>
> when: "{{inventory_hostname == 'icinga.example.com'}}"
>
> to the other tasks.  Small price to pay.
>
> Thank you.

Chris, you can still use "hosts: icinga.example.com" and iterate over the all group:

{% for host in groups['all'] %}
...
{% endfor %}

BTW: the when condition is automatically evaluated by Jinja, so drop the curly braces.

Regards
Racke

>
> On Thursday, December 9, 2021 at 1:12:39 AM UTC-8 ra...@linuxia.de wrote:
>
> On 09/12/2021 10:07, Chris Jefferies wrote:
> > Racke,
> > *ansible_play_hosts* - I did not know about this *magic* variable, as they call it.  I'll test but I assume that the attributes come with it.
> >
> > Then you describe defining a task with:
> >
> > run_once: yes
> > delegate_to: localhost
> >
> > I see run_once in the documentation and they said it was like running only on the first host; which is fine because now I want to run using *ansible_play_hosts* which gets me all the hosts.
> >
> > Then instead of using:
> > delegate_to: localhost
> >
> > I think I can delegate to the server I am actually running against:

> > delegate_to: icinga.example.com <http://icinga.example.com>
>
> Chris,
>
> yes you can use icinga.example.com <http://icinga.example.com> if that host is part of your inventory.

>
> Racke
>
>
> >
> > Or are you suggesting I delegate to localhost, then copy the resulting file?
> >
> > dick,
> > I hope the above result explains what and how I would like to do.  But to explain a bit... I want to end up with a file that has something like this content, below.  I was trying to figure out a way to subvert the normal processing of an inventory host file and do it all into one file.  Racke has show a way of doing this by using a "magic variable" that holds all of the host info I need and how to run it only once so I don't get a bunch of repetitive files being generated.  It's beautiful...  if it works.  ;)   I'm sure it will.
> >

> > object Host "myhost1.mine.me <http://myhost1.mine.me>" {

> >   import "generic-host"
> >   address = "192.68.0.1"
> >   vars.os = "Linux"
> > }

> > object Host "myhost2.mine.me <http://myhost2.mine.me>" {

> > > To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com> <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com>> <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com?utm_medium=email&utm_source=footer <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com?utm_medium=email&utm_source=footer> <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/ansible-project/5b0de281-4c29-49f7-bbcf-0fe2ef957b70n%40googlegroups.com?utm_medium=email&utm_source=footer>>>.
> >
> >
> > --
> > Ecommerce and Linux consulting + Perl and web application programming.
> > Debian and Sympa administration.
> >
> >
> > --
> > You received this message because you are subscribed to the Google Groups "Ansible Project" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to ansible-proje...@googlegroups.com <mailto:ansible-proje...@googlegroups.com>.

> > To view this discussion on the web visit https://groups.google.com/d/msgid/ansible-project/c0dbc61d-15d1-4ec5-8635-99f42b85fd3en%40googlegroups.com <https://groups.google.com/d/msgid/ansible-project/c0dbc61d-15d1-4ec5-8635-99f42b85fd3en%40googlegroups.com> <https://groups.google.com/d/msgid/ansible-project/c0dbc61d-15d1-4ec5-8635-99f42b85fd3en%40googlegroups.com?utm_medium=email&utm_source=footer <https://groups.google.com/d/msgid/ansible-project/c0dbc61d-15d1-4ec5-8635-99f42b85fd3en%40googlegroups.com?utm_medium=email&utm_source=footer>>.

>
>
> --
> Ecommerce and Linux consulting + Perl and web application programming.
> Debian and Sympa administration.
>
>

> --
> You received this message because you are subscribed to the Google Groups "Ansible Project" group.
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[ch...@freeranger.com]

Racke.

-- {% for host in groups['all'] %}

Beautiful.  Thanks.