How to pass variable from one playbook to another playbook ? Ansible

In Ansible, passing a variable from one playbook to another playbook is not a straight forward. (If the target hosts are different). We might need to get the variable value from one host and use that value against another host in some cases. This article will provide a solution to overcome this kind of tricky situation in Ansible.

Here are the scenarios of passing a variable from one playbook to another playbook or register a variable to persist between plays in Ansible.

• Two playbooks which target single host – In the same play
• Two playbooks which target different hosts – In the same play

 

Environment: 

• Ansible Engine: 2.7

 

Register a variable to persist between plays in Ansible – Same target host:

Here are the master playbook contents which includes other two playbooks.

[root@ansible-server ~]# cat global.yaml
---
# Combine multiple playbooks
  - import_playbook: test.play1.yaml
  - import_playbook: test.play2.yaml
[root@ansible-server ~]#

 

 Playbook contents: test.play1.yaml

In test.play1 playbook, we are registering new variable “PLAY1VAR”  to use it in the second playbook.

---
- hosts: localhost
  gather_facts: false

  tasks:
   - name: Register a new value
     shell: echo "/etc/resolv.conf"
     register: PLAY1VAR

   - debug: msg="{{PLAY1VAR.stdout}}"

 

Playbook contents: test.play2.yaml 

In test.play2 playbook, we are using “PLAY1VAR”  to view the last line of the file content and registering the result in PLAY2_RESULTS variable.

---
- hosts: localhost
  gather_facts: false

  tasks:
   - name: Echo the output - PLAY1 variable vaule
     shell: cat "{{PLAY1VAR.stdout}}" |tail -1
     register: PLAY2_RESULTS

   - debug: msg="{{PLAY2_RESULTS.stdout}}"

 

Test our work:

[root@ansible-server ~]# ansible-playbook -i localhost global.yaml
PLAY [localhost] *******************************************************************

TASK [Register a new value] *********************************************************
changed: [localhost]

TASK [debug] *************************************************************************
ok: [localhost] => {
    "msg": "/etc/resolv.conf"
}

PLAY [localhost] *********************************************************************

TASK [Echo the output - PLAY1 variable vaule] ***************************************************************************************
changed: [localhost]

TASK [debug] *************************************************************************
ok: [localhost] => {
    "msg": "nameserver 192.168.3.2"
}

PLAY RECAP ****************************************************************************
localhost                  : ok=4    changed=2    unreachable=0    failed=0

[root@ansible-server ~]# 

 

We have successfully passed the variable from one playbook to another playbook (It the target host is the same). We have got the desired results.

 

Register a variable to persist between plays in Ansible – Different Target Hosts

What will happen if the target hosts are different? I have modified the test.play2.yaml‘s target host and test.play1.yaml still points to localhost. Let me re-run the job to check the results.

 

[root@ansible-server ~]# ansible-playbook -i inventory_1 global.yaml

PLAY [localhost] **********************************************************************

TASK [Register a new value] ***********************************************************
changed: [127.0.0.1]

TASK [debug] ***************************************************************************
ok: [127.0.0.1] => {
    "msg": "/etc/resolv.conf"
}

PLAY [192.168.3.151] ******************************************************************
TASK [Echo the output - PLAY1 variable vaule] *****************************************
fatal: [192.168.3.151]: FAILED! => {"msg": "The task includes an option with an undefined 
variable. The error was: 'PLAY1VAR' is undefined\n\nThe error appears to have been in 
'/root/test.play2.yaml': line 6, column 6, but may\nbe elsewhere in the file depending 
on the exact syntax problem.\n\nThe offending line appears to be:\n\n  tasks:\n   
- name: Echo the output - PLAY1 variable vaule\n     ^ here\n"}

PLAY RECAP ****************************************************************************
127.0.0.1                  : ok=2    changed=1    unreachable=0    failed=0
192.168.3.151              : ok=0    changed=0    unreachable=0    failed=1
[root@ansible-server ~]#

 

The Ansible play failed due to an undefined variable (PLAY1VAR)in test.play2.yaml file. We have got the most common error – “The task includes an option with an undefined variable“.

 

Solution:

1. Make the changes on test.play1.yaml.Highlighted the changes.

---
- hosts: localhost
  gather_facts: false

  tasks:
   - name: Register a new value
     shell: echo "/etc/resolv.conf"
     register: PLAY1VAR

   - debug: msg="{{PLAY1VAR.stdout}}"

   - name: Register dummy host with variable
     add_host:
       name: "DUMMY_HOST"
       PLAY1VAR_NEW: " {{ PLAY1VAR.stdout }}"

 

2. Make the change like below on test.play2.yaml. Highlighted the changes.

---
- hosts: 192.168.3.151
  gather_facts: false

  tasks:
   - name: Echo the output - PLAY1 variable vaule
     shell: cat {{ hostvars['DUMMY_HOST']['PLAY1VAR_NEW'] }} |tail -1
     register: PLAY2_RESULTS

   - debug: msg="{{PLAY2_RESULTS.stdout}}"

 

3. Re-run the playbook and check the results.

[root@ansible-server ~]# ansible-playbook -i inventory_1 global.yaml

PLAY [localhost] ************************************************************

TASK [Register a new value] *************************************************
changed: [127.0.0.1]

TASK [debug] ***************************************************************&
ok: [127.0.0.1] => {
    "msg": "/etc/resolv.conf"
}

TASK [add_host] *************************************************************
changed: [127.0.0.1]

PLAY [192.168.3.151] ********************************************************

TASK [Echo the output - PLAY1 variable vaule] ******************************************************************************
changed: [192.168.3.151]

TASK [debug] *****************************************************************
ok: [192.168.3.151] => {
    "msg": "nameserver 192.168.3.2"
}

PLAY RECAP ******************************************************************
127.0.0.1                  : ok=3    changed=2    unreachable=0    failed=0
192.168.3.151              : ok=2    changed=1    unreachable=0    failed=0

[root@ansible-server ~]#

 

We have successfully carried the registered variable from one playbook to another on different target hosts.

 

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