Request adding documentation on how to configure the system/user locale

[brlin-tw]

I was looking for information on solving the following Ansible task error, to be specific:

TASK [ossii.init : Configure preferred UI localization settings(Systemd-based distros)] ***********
fatal: [host]: FAILED! => 
    changed: false
    cmd:
    - localectl
    - set-locale
    - LANGUAGE=zh_TW:zh:en
    delta: '0:00:00.008622'
    end: '2025-09-19 09:46:24.236281'
    failed_when_result: true
    msg: non-zero return code
    rc: 1
    start: '2025-09-19 09:46:24.227659'
    stderr: 'Failed to issue method call: Locale zh_TW:zh:en not installed, refusing.'
    stderr_lines: <omitted>
    stdout: ''
    stdout_lines: <omitted>

[sspencerwire]

Hi @brlin-tw I do not know if any of this will answer your question, but have you checked out this resource: https://docs.rockylinux.org/books/learning_ansible/00-toc/ If that is of no help, I can ask @alemorvan who has worked quite a bit with ansible if he knows the answer.

[NezSez]

Note that 'man localectl' states that the initrd is not rebuilt by using it, and must be done manually, but is only needed if the locale is required in the early boot stages apparently.
'locale' will list the current settings
'locale -a' will list all the installed locales
As the error indicates, "Locale zh_TW:zh:en not installed" because it doesn't match anything in the locale database.
For the ansible 'cmd' maybe the "LANGUAGE=" should be just "zh_TW" or "zh_TW.utf8"?

[alemorvan]

Maybe using something like that:

- name: Configure LANGUAGE in /etc/locale.conf
  ansible.builtin.lineinfile:
    path: /etc/locale.conf
    regexp: '^LANGUAGE='
    line: 'LANGUAGE=zh_TW'
    create: yes
  become: true

Try not to use cmd when possible.