Comment 2 for bug 1967798

Reviewed: https://review.opendev.org/c/starlingx/distcloud/+/836400
Committed: https://opendev.org/starlingx/distcloud/commit/d9af1bf0ec17955d9a76800448189b37443fd6b6
Submitter: "Zuul (22348)"
Branch: master

commit d9af1bf0ec17955d9a76800448189b37443fd6b6
Author: Li Zhu <email address hidden>
Date: Mon Apr 4 15:42:02 2022 -0400

    Fix prestage playbook access to subcloud denied when host key changes

    Steps to Reproduce:
    1 Upgrade system controller
    2 Upgrade subcloud
    3 prestage subcloud for reinstallation

    The issue came from “Upgrade Subcloud” rather than prestage. At the
    end of upgrade, it restored the old ssh configurations including
    public keys on the subclouds which cause the ssh authentication
    failed in the next step.

    This is a generic fix for all of the playbooks (eg. reinstall,
    upgrade, prestage, etc.). This UserKnownHostsFile=/dev/null ssh
    option will make sure not save the host key as trusted for added
    security no matter the host key changed or not. It combined with
    the existing StrictHostKeyChecking=no option will disable
    the public key checking for ssh connections.

    Test Plan:

    PASS:
    - Verify installation without failures
    - Verify upgrade subclouds without any access failures
    - Verify prestage without subclouds access failures
    - Verify no subclouds access failures according to the given
      100% reproducible steps.

    Closes-Bug: 1967798
    Signed-off-by: Li Zhu <email address hidden>
    Change-Id: I100a65845875d93666f7e6b60b92f8e9add653e4