Ansible known_hosts module ssh key propagation question - jenkins

Question

I'm trying to craft a playbook that will update the known_hosts for a machine / user however I'm getting an error I can't make sense of.
---
- name: Keys
hosts: adminslaves
gather_facts: false
no_log: false
remote_user: test
#pre_tasks:
# - setup:
# gather_subset:
# - '!all'
tasks:
- name: Scan for SSH host keys.
shell: ssh-keyscan myhost.mydomain.com 2>/dev/null
changed_when: False
register: ssh_scan
# - name: show vars
# debug:
# msg: "{{ ssh_scan.stdout_lines }}"
#
- name: Update known_hosts.
known_hosts:
key: "{{ item }}"
name: "{{ ansible_host }}"
state: present
with_items: "{{ ssh_scan.stdout_lines }}"
My error is "msg": "Host parameter does not match hashed host field in supplied key"}
I think the variable has the right information (at least it does when I debug it).
My end goal is a playbook that will add ssh keys of a list of hosts to a list of hosts for Jenkins auth.
Appreciate any help.

Answer 1

the problem is that the output of ssh-keyscan myhost.mydomain.com 2>/dev/null usually contains more than one key so you need to process it.
Someone with the same error message raised an issue, but again the problem was with the ssh-key format. I better understood checking the code used by known_hosts task.
Here the code I use:
- name: Populate known_hosts
hosts: spectrum_scale
tags: set_known_hosts
become: true
tasks:
- name: Scan for SSH keys
ansible.builtin.shell:
cmd: "ssh-keyscan {{ hostvars[spectrum_scale].ansible_fqdn }}
{{ hostvars[spectrum_scale].ansible_hostname }}
{{ hostvars[spectrum_scale].ansible_default_ipv4.address }}
2>/dev/null"
loop: "{{ groups['spectrum_scale'] }}"
loop_control:
loop_var: spectrum_scale
register: ssh_scan
- name: Set stdout_lines array for ssh_scan
set_fact:
ssout: []
- name: Fill ssout
set_fact:
ssout: "{{ ssout + ss_r.stdout_lines }}"
loop: "{{ ssh_scan.results }}"
loop_control:
loop_var:
ss_r
when: ss_r.stdout_lines is defined
- name: Add client ssh keys to known_hosts
ansible.builtin.known_hosts:
name: "{{ hk.split()[0] }}"
key: "{{ hk }}"
state: present
loop: "{{ ssout }}"
loop_control:
loop_var: hk