Ansible register fails when there is no output from shell

Question

So basically i want to check somehow if the /dev/xvdb1 is mounted to /var

If answer is yes:

don't create dir
don't copy files
don't mount /var etc

If the answer is no:

proceed with everything

- name: check if /var is mounted
  shell: df -hT | grep /var
  register: df

- name: Create /mnt/newvar directory
  file: 
    path: "{{ newvar_dir }}"
    state: directory
  when: not df.stdout_lines

- name: "Get UUID for partition"
  shell: "lsblk -no UUID /dev/xvdb1"
  register: volume_uuids

- name: Mount /mnt/newvar to /dev/xvdb1
  mount:
    path: "{{ newvar_dir }}"
    src: "UUID={{ item }}"
    fstype: "{{ volume_filesystem_type }}"
    opts: "defaults,noauto"
    state: mounted
  with_items: 
    - "{{ volume_uuids.stdout_lines }}"
  when: not df.stdout_lines

Error: fatal: [x.x.x.x]: FAILED! => {"changed": true, "cmd": "df -hT | grep /var", "delta": "0:00:00.005132", "end": "2019-03-10 03:07:22.485343", "msg": "non-zero return code", "rc": 1, "start": "2019-03-10 03:07:22.480211", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}

The issue is: if there is no output from df command, ansible brakes.

M I P M I P · Accepted Answer · 2019-03-10T09:34:32

You could you ansible_mounts fact to see if the mount exists and set_fact to define a new variable, instead of using df and registering results.

See below for reference:

- name: Check if /var mount exists
  set_fact:
    is_var_mounted: true
  when: item.mount == "/var"
  with_items: "{{ ansible_mounts }}"

- name: Do everything you want to do if not mounted
  debug:
     msg: "Doing Things"
  when: is_var_mounted is not defined

- name: Skip steps if mounted
  debug:
     msg: "Skipping"
  when: is_var_mounted is defined

Ansible register fails when there is no output from shell

2 Answers