# Jinja2 and a nested list of lists

**URL:** <https://forum.ansible.com/t/jinja2-and-a-nested-list-of-lists/5083>\
**Category:** Get Help\
**Created:** [April 23, 2024, 6:12am UTC](https://forum.ansible.com/t/jinja2-and-a-nested-list-of-lists/5083 "2024-04-23T06:12:19Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![microlinux](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/microlinux/32/2968_2.png) [@microlinux](https://forum.ansible.com/u/microlinux)\
**Post date:** [April 23, 2024, 6:12am UTC](https://forum.ansible.com/t/jinja2-and-a-nested-list-of-lists/5083/1 "2024-04-23T06:12:19Z")

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Hi,

I’m new to this forum, so allow me to introduce myself. I’m an Austrian IT guy living in South France, I’m working daily with Linux, and I discovered Ansible a few months back.

I’m slowly but steadily adopting it for real work. It’s a slippery fish, but once you get the hang of it, you won’t miss it.

So right, here goes. I’ve written a playbook to manage my (local and public) backup servers using Rocky Linux and Rsnapshot. To write the `rsnapshot.conf` configuration file, I used a Jinja2 template file. Here’s a snippet from the file:

```auto
#######################
# BACKUP TARGET HOSTS #
#######################

{% for backup_target in backup_targets %}
# {{ backup_target }}
{% for backup_dir in backup_dirs %}
backup root@{{ backup_target }}:{{ backup_dir}} {{ backup_target }}
{% endfor %}

{% endfor %}

```

The corresponding variables are in the `host_vars` section and look like this:

```auto
backup_targets:
  - alphamule.microlinux.lan
  - gustave.microlinux.lan
  - proxy.microlinux.lan
backup_dirs:
  - /etc
  - /home

```

With all this, here’s what the resulting configuration file on the target looks like:

```auto
#######################
# BACKUP TARGET HOSTS #
#######################

# alphamule.microlinux.lan
backup root@alphamule.microlinux.lan:/etc alphamule.microlinux.lan
backup root@alphamule.microlinux.lan:/home alphamule.microlinux.lan

# gustave.microlinux.lan
backup root@gustave.microlinux.lan:/etc gustave.microlinux.lan
backup root@gustave.microlinux.lan:/home gustave.microlinux.lan

# proxy.microlinux.lan
backup root@proxy.microlinux.lan:/etc proxy.microlinux.lan
backup root@proxy.microlinux.lan:/home proxy.microlinux.lan

```

So far this works fine.

Now here comes the tricky part. For now I’m assuming that Rsnapshot does backups of the same directory trees on every host, e. g. `/etc` and `/home` in the example above.

I’m now encountering a situation where I have different `backup_dirs` for different `backup_targets`. Something like this:

```auto
- alphamule.microlinux.lan:
    - /etc
    - /home
- gustave.microlinux.lan:
    - /home
- proxy.microlinux.lan:
    - /etc
    - /var
    - /srv

```

How can I make Jinja2 loop over this list of lists? I _think_ this is a list of lists… I have yet to bend my head around all the things YAML. It looks like I’m missing some IQ points to translate this into correct Jinja2 syntax. So I thought I’d ask the competent crowd in this forum for a little help.

Cheers from the sunny South of France,

Niki

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**Author:** ![x9c4](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/x9c4/32/728_2.png) [@x9c4](https://forum.ansible.com/u/x9c4)\
**Post date:** [April 23, 2024, 7:33am UTC](https://forum.ansible.com/t/jinja2-and-a-nested-list-of-lists/5083/2 "2024-04-23T07:33:52Z")

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Can I for a moment assume that you control that file? What you got there is actually a list of dictionaries with one key and a list as a value. How about you create a variable containing a dictionary of lists? Like this:

```yaml
backup_targets:
  alphamule.microlinux.lan:
    - /etc
    - /home

```

Or (probably even more future proof), a list of items with name and directories:

```yaml
backup_targets:
  - name: alphamule
    fqdn: alphamule.microlinux.lan
    dirs:
      - /etc
      - /home
  - name: gustave
    fqdn: gustave.microlinux.lan
    dirs:
      - /home
...

```

(You woudn’t need the name attributes now, but that’s how it’s extendable.)  
Your template should then look like

```jinja2
{%- for backup_target in backup_targets %}
# {{ backup_target.name }}
{%- for backup_dir in backup_target.dirs %}
backup root@{{ backup_target.fqdn }}:{{ backup_dir}} {{ backup_target.fqdn }}
{% endfor %}

{% endfor %}

```

[not tested, expect typos]

Enjoy the sun!

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<div class="post-metadata">

**Author:** ![microlinux](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/microlinux/32/2968_2.png) [@microlinux](https://forum.ansible.com/u/microlinux)\
**Post date:** [April 23, 2024, 2:17pm UTC](https://forum.ansible.com/t/jinja2-and-a-nested-list-of-lists/5083/3 "2024-04-23T14:17:30Z")

</div>

Thanks very much ! I experimented some more and now everything works perfectly as expected.

Cheers !

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/ansible/original/1X/1882d9a01da5d8996a862359b0913cc568a39b84.svg) [@system](https://forum.ansible.com/u/system)\
**Post date:** [May 23, 2024, 2:18pm UTC](https://forum.ansible.com/t/jinja2-and-a-nested-list-of-lists/5083/4 "2024-05-23T14:18:12Z")

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Closed on May 23, 2024, 2:18pm UTC

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