Ansible - using with_items and when conditional to

问题

I have a bunch of servers that have four physical drives on them (/dev/sda, sdb, sdc, and sdd). sda has the OS installed on it.

I need to format each drive except sda. I need to check if each drive has data on it. If it does, then I shouldn't format it.

# This will get all physical disks (sda, sdb, sdc, etc) and assign them to disk_var
- name: Get disks
  set_fact: disk_var="{{hostvars[inventory_hostname]["ansible_devices"].keys()|list}}"

- name: Check if the disk is partitioned and also ignore sda
  stat: path=/dev/{{item}}1
  with_items: disk_var
  when: item != 'sda'
  register: base_secondary_partition_{{item}}

- name: Create GPT partition table
  command: /sbin/parted -s /dev/{{item}} mklabel gpt
  with_items: disk_var
  when: item != 'sda' and base_secondary_partition_{{item}}.stat.exists == false

There's clearly more steps involved into formatting these drives but it fails at the last task when creating the GPT partition table.

Here's what it looks like when it runs. You'll see that it fails at the last task:

TASK: [role | Get disks] ******************************************************
ok: [server1.com]

TASK: [role | Check if the disk is partitioned] *******************************
skipping: [server1.com] => (item=sda)
ok: [server1.com] => (item=sdd)
ok: [server1.com] => (item=sdb)
ok: [server1.com] => (item=sdc)

TASK: [role | Create GPT partition table] *************************************
fatal: [server1.com] => error while evaluating conditional: base_secondary_partition_sdd.stat.exists == false

FATAL: all hosts have already failed -- aborting

Any idea how I can check the conditional base_secondary_partition_{{item}}.stat.exists? I need to make sure that if there's data on the drive, it will not format it.

回答1:

You do not need to register your result with the item salt. When you register the result of a loop (e.g. with_items) the registered value will contain a key results which holds a list of all results of the loop. (See docs)

Instead of looping over your original device list, you can loop over the registered results of the first task then:

- name: Check if the disk is partitioned and also ignore sda
  stat: path=/dev/{{item}}1
  with_items: disk_var
  when: item != 'sda'
  register: device_stat

- name: Create GPT partition table
  command: /sbin/parted -s /dev/{{ item.item }} mklabel gpt
  with_items: "{{ device_stat.results }}"
  when:
    - not item | skipped
    - item.stat.exists == false

The condition not item | skipped takes care of that elements which have been filtered in the original loop (sda) will not be processed.

While that might be a solution to your problem, your question is very interesting. There seems to be no eval feature in Jinja2. While you can concatenate strings you can not use that string as a variable name to get to its value...

回答2:

Your tasks can be as simple as this...

- stat:
    path: /dev/{{item}}1
  with_items: ansible_devices.keys()
  when: item != 'sda'
  register: stats
- command: /sbin/parted -s /dev/{{item.item}} mklabel gpt
  with_items: stats.results
  when: item.stat | default(false) and item.stat.exists

来源：https://stackoverflow.com/questions/32214529/ansible-using-with-items-and-when-conditional-to

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