Ansible to create users and assign them to a particular group based on vars - linux

Question

Gurus, I'm learning ansible and trying to understand how the variables can be used, i have come across writing below playbook but i'm not understanding How to assign a particular group to particular users based on the Variables i have defined in the play for both Users and Groups under vars
I have below play where i want to create Users anika and rigved and want to assign them to a docker group while ayush and eshant should have the test group assigned.
I'm not getting the idea to achieve this so far. However as of now while running it creates users and assigns both group to all users.
$ cat nested_playbook-1.yml
---
- name: testing nested play
hosts: localhost
vars:
users:
- anika
- rigved
- ayush
- eshant
grps:
- docker
- test
tasks:
- name: make users members of groups
user:
name: "{{ item[0] }}"
state: present
groups: "{{ item[0] }}"
with_nested:
- "{{ users }}"
- "{{ grps }}"

Answer 1

The way you've structured your data doesn't show any relationship between users and groups. One option would be to structure it like this:
grps:
- name: docker
users:
- anika
- rigved
- name: test
users:
- ayush
- eshant
With this structure, you can loop over grps using the subelements filter, like this:
---
- name: testing nested play
gather_facts: false
hosts: localhost
vars:
grps:
- name: docker
users:
- anika
- rigved
- name: test
users:
- ayush
- eshant
tasks:
- debug:
msg:
user:
name: "{{ item.1 }}"
state: present
groups: "{{ item.0.name }}"
loop: "{{ grps|subelements('users') }}"
loop_control:
label: "{{ item.1 }}"
The subelements filter is a way of creating a "nested loop": it iterates over each member of the 'users' key for each group in grps. During each loop iteration, item is a 2-tuple in which the first item is the corresponding element from grps and the second item iterates over the users key for that element. In other words, you end up iterating over this list:
[{'name': 'docker', 'users': ['anika', 'rigved']}, anika}
[{'name': 'docker', 'users': ['anika', 'rigved']}, rigved}
[{'name': 'test', 'users': ['ayush', 'eshant']}, ayush}
[{'name': 'test', 'users': ['ayush', 'eshant']}, eshant}
So within the loop, item.0 refers to the group entry itself (and thus item.0.name is the group name), and item.1 refers to the user.
PLAY [testing nested play] *******************************************************************
TASK [debug] *********************************************************************************
ok: [localhost] => (item=anika) => {
"msg": {
"user": {
"groups": "docker",
"name": "anika",
"state": "present"
}
}
}
ok: [localhost] => (item=rigved) => {
"msg": {
"user": {
"groups": "docker",
"name": "rigved",
"state": "present"
}
}
}
ok: [localhost] => (item=ayush) => {
"msg": {
"user": {
"groups": "test",
"name": "ayush",
"state": "present"
}
}
}
ok: [localhost] => (item=eshant) => {
"msg": {
"user": {
"groups": "test",
"name": "eshant",
"state": "present"
}
}
}
PLAY RECAP ***********************************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Alternately, you could structure your data like this:
users:
- name: anika
group: docker
- name: rigved
group: docker
- name: ayush
group: docker
- name: eshant
group: docker
You can just use a simple loop to process this structure:
---
- name: testing nested play
gather_facts: false
hosts: localhost
vars:
users:
- name: anika
group: docker
- name: rigved
group: docker
- name: ayush
group: docker
- name: eshant
group: docker
tasks:
- debug:
msg:
user:
name: "{{ item.name }}"
state: present
groups: "{{ item.group }}"
loop: "{{ users }}"
loop_control:
label: "{{ item.name }}"
Note that in both the above examples I'm using loop_control on the tasks just to set the loop label and make the output look nicer. You could remove loop_control from the above tasks with no impact on how they operate.