如何使用Ansible干净地管理printers.conf？

我有以下Ansible playbook文件，它试图在一组CentOS 6设备上管理printers.conf

---
# file: roles/common/tasks/config-cups.yml
# Configure printing

- name: ensure cups is installed
  yum: pkg=cups state=installed

# We want to compare the local and remote printers.conf files so that
# we can predetermine if the copy needs to happen.  According to a
# comment in the default printers.conf file, we can't write
# printers.conf while cups is running. But to be idempotent, we want
# to avoid stopping the cups service if we don't need to.

- stat: path=printers.conf
  register: locst

- stat: path=/etc/cups/printers.conf
  register: remst

# can't write printers.conf while running, so says the default file
- name: ensure cups is stopped
  service: name=cups state=stopped
  when: locst.stat.md5 ne remst.stat.md5

- name: Configure printers
  tags: configuration
  copy: >
    src=printers.conf
    dest=/etc/cups/printers.conf
    mode=600 owner=root group=lp
  notify:
  - restart cups

- name: Enable the cups service
  service: name=cups enabled=yes

- name: Ensure cups is running
  service: name=cups state=started

不幸的是，当条件控制cups服务停止时，我从

接收到错误“fatal:[hostxxx]=>error when evaluation conditional:locst.stat.md5 ne remst.stat.md5”

是否有办法查看正在计算的条件中的值？在这里添加
-vvv
对我没有帮助

或者是否有其他方法调试条件语句

EDIT1:

显然，stat模块总是远程的——它无法与roles/common/files/printers.conf中的local printers.conf匹配

TASK: [common | stat path=printers.conf] **************************************
<hostxxx> ESTABLISH CONNECTION FOR USER[...]
<hostxxx> REMOTE_MODULE stat path=printers.conf
[...]
ok: [hostxxx] => {"changed": false, "stat": {"exists": false}}

然而，我确实注意到md5值出人意料地不同。似乎在运行时，cups会重新写入printers.conf文件，其中包括一个名为“StateTime”的时间戳。通过编写配置文件来管理cups的简单方法到此为止

AFAICT是清洁管理cups的唯一方法，因此每次只能关闭服务，要么在比较之前过滤现有的printers.conf，要么就不那么合理，要编写webscraper以针对cups希望您用于配置打印机的接口进行操作。
假设ansible仅在文件不同时运行validate命令，因此将尝试替换该文件，您可以“扩展”validate功能以停止cups：

- name: Configure printers
  tags: configuration
  copy: src=printers.conf dest=/etc/cups/printers.conf mode=600 owner=root group=lp validate="service cups stop %s"

- name: Ensure cups is running
  service: name=cups state=started

%s对于服务来说是多余的（但对我的debian系统没有影响），但是根据文档，ansible是必需的。参见
我试图从阿列克斯金那里得到答案，但无法让“扩展”正常工作。因此，以下是我最终得到的（测试和工作）

根据我对Ansible工作原理的理解，您不需要检查文件是否不同——这是复制模块中已经发生的事情

嗯,

Russell.
您的方法可能存在一些潜在问题：


-stat:path=printers.conf
指的是远程位置，而不是
{{playbook\u dir}}/roles/common/
默认情况下未启用md5处理。您需要明确地编写
get\u md5=yes
运行playbook的用户可能需要具有stat
/etc/cups/printers.conf

根据您的问题提出的解决方案：

---
- name: "cups - installation"
  apt: name=cups state=installed update_cache=yes cache_valid_time=3600
  become: yes

- name: "cups - md5 on local printers.conf"
  local_action: stat path={{ playbook_dir }}/roles/homie/files/printers.conf get_md5=yes
  register: locst

- name: "cups - md5 on remote printers.conf"
  stat: path=/etc/cups/printers.conf get_md5=yes
  register: remst
  become: yes

- name: "cups - stop service"
  service: name=cups state=stopped
  when: not remst.stat.exists or (locst.stat.md5 != remst.stat.md5)
  become: yes

- name: "cups - configure drivers"
  copy: src=Canon_MG2900_series.ppd dest=/etc/cups/ppd/Canon_MG2900_series.ppd mode=640 owner=root group=lp backup=yes 
  become: yes

- name: "cups - configure printers"
  copy: src=printers.conf dest=/etc/cups/printers.conf mode=600 owner=root group=lp backup=yes
  notify: restart cups
  when: not remst.stat.exists or (locst.stat.md5 != remst.stat.md5)
  become: yes

和处理程序：

---
- name: restart cups
  service: name=cups state=restarted
  become: yes

使用ansible 2.1.0.0
我在前面的-vvv输出中找到了错误源：“stat path=printers.conf”与本地文件不匹配。
---
- name: "cups - installation"
  apt: name=cups state=installed update_cache=yes cache_valid_time=3600
  become: yes

- name: "cups - md5 on local printers.conf"
  local_action: stat path={{ playbook_dir }}/roles/homie/files/printers.conf get_md5=yes
  register: locst

- name: "cups - md5 on remote printers.conf"
  stat: path=/etc/cups/printers.conf get_md5=yes
  register: remst
  become: yes

- name: "cups - stop service"
  service: name=cups state=stopped
  when: not remst.stat.exists or (locst.stat.md5 != remst.stat.md5)
  become: yes

- name: "cups - configure drivers"
  copy: src=Canon_MG2900_series.ppd dest=/etc/cups/ppd/Canon_MG2900_series.ppd mode=640 owner=root group=lp backup=yes 
  become: yes

- name: "cups - configure printers"
  copy: src=printers.conf dest=/etc/cups/printers.conf mode=600 owner=root group=lp backup=yes
  notify: restart cups
  when: not remst.stat.exists or (locst.stat.md5 != remst.stat.md5)
  become: yes

---
- name: restart cups
  service: name=cups state=restarted
  become: yes