Ansible Replace InLine Results in Wrong Content Hosts File - ansible

Question

I'm using the following task to update /etc/hosts file on my inventory, but strangely I see a different alias being enetered.
- debug:
msg: "hostname = {{ inventory_hostname }} has ansible_fqdn = {{ ansible_fqdn }} and ansible_ipv4 = {{ ansible_default_ipv4.address }} and ansible_hostname = {{ ansible_hostname }}"
- name: Fix /etc/hosts removing the old hostname
become: true
throttle: 1
lineinfile:
state=present
dest=/etc/hosts
line="{{ ansible_default_ipv4.address }} {{ inventory_hostname }} {{ ansible_hostname }}"
regexp="^{{ ansible_default_ipv4.address }}"
The output of the debug statement is:
TASK [common : debug] ***********************************************************************************************************************************************************************************************
ok: [n2.open-electrons.com] => {
"msg": "hostname = n2.my-host.com has ansible_fqdn = n2.my-host.com and ansible_ipv4 = 192.168.0.203 and ansible_hostname = n2"
}
But when I SSH into the remote machine, I get to see the following in my /etc/hosts:
127.0.1.1 n2.my-host.com n1
127.0.0.1 localhost
Any ideas as to what might have gone wrong? I have another machine in the inventory which is configured as n1.my-host.com, but how come the alias is getting messed up?
My inventory file:
[master]
m1.my-host.com ansible_host=192.168.0.100
[node]
n1.my-host.com ansible_host=192.168.0.102
n2.my-host.com ansible_host=192.168.0.103
[k3s_cluster:children]
master
node
[all:vars]
ansible_python_interpreter=/usr/bin/python3

Answer 1

Any ideas as to what might have gone wrong? ... how come the alias is getting messed up?
Because of the hint within your example code
- name: Fix /etc/hosts removing the old hostname
it is assumed that your are going to change the hostnames of the Remote Nodes.
Therefore the issue might be caused by the fact that the content of ansible_hostname is a gathered fact on the Remote Node dynamically during runtime and by the setup module, whereby the inventory_hostname is a Special variable from the inventroy file on the Control Node.
inventory_hostname The inventory name for the ‘current’ host being iterated over in the play
inventory_hostname_short The short version of inventory_hostname
So to prevent a mismatch of information from different sources you could use the approach of single source of truth.
- name: Fix /etc/hosts removing the old hostname
become: true
lineinfile:
path: /etc/hosts
regexp: "^{{ ansible_default_ipv4.address }}"
line: "{{ ansible_default_ipv4.address }} {{ inventory_hostname }} {{ inventory_hostname_short }}"
state: present
Please notice that on the Remote Node itself can be also different sources for the hostname. Therefore you might need not only to change it on /etc/hosts but also in several different parts
- name: Set hostname to inventory_hostname
shell:
cmd: "nmcli general hostname {{ inventory_hostname }} && nmcli general hostname"
depending on your target system even
hostnamectl