How to properly setup EC2 instance hostname?

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1

Dear community,

I have another issue I can’t wrap my head around. Possibly because I stared on the screen for too long, maybe because I’m to stupid.

Anyways, I want to create an AWS EC2 instance (Debian Strecht → which obviously uses cloud-init) with a custom hostname. Not the EC2 public/private hostname but
the os hostname.

Usually I would use the Ansible’s hostname module to change /etc/hostname but I also want to permantly change /etc/hosts.

So I thought it would be best to “inject” my custom hostname during the instance setup via a user-data script. I thought this might cause cloud-init to pick up my custom hostname instead of the one that is automatically created from the private ip-address.

My first question now is: Is that possible? Can I manipulate the initial setup process of the instance to use my custom hostname?

If yes, this would be a huge relief. But that raise the question of how I can achieve that.

This is the piece of my playbook which creates the EC2 instance:

`

  • name: Create ec2 instance
    ec2:
    key_name: “{{ keypair }}”
    vpc_subnet_id: “{{ vpc_subnet_id }}”
    group_id: “{{ security_group_id }}”
    instance_type: “{{ instance_type }}”
    image: “{{ image }}”
    wait: true
    region: “{{ region }}”
    instance_tags: “{{ tags }}”
    volumes:

  • device_name: xvda
    volume_type: gp2
    volume_size: “{{ volume_size }}”
    delete_on_termination: “{{ delete_on_termination }}”
    assign_public_ip: “{{ assign_public_ip }}”
    termination_protection: “{{ termination_protection }}”
    no_log: true
    register: ec2

  • name: Wait for SSH to come up
    wait_for: host={{ item.private_ip }} port=22 delay=30 timeout=320 state=started
    no_log: true
    with_items: ‘{{ ec2.instances }}’

  • name: Add new instance to host group
    add_host: hostname={{ item.private_ip }} groupname=launched
    no_log: true
    with_items: ‘{{ ec2.instances }}’
    `

I could imagine that I add something like “user_data: “”” to the ec2 block, but I’m not sure about the correct syntax to manipulate the hostname accordingly.

Can someone assist me on that matter?

Best regards
René

2

Okay, I found out that it is actually possible to manipulate hostname and fqdn during the instance creation.

I tested it (https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/4/html/End_User_Guide/user-data.html) with a simple text file which looks like this:

#cloud-config
hostname: test1234
fqdn: test1234.example.local

What I didn’t figure out yet is how to integrate that into my playbook.

Best regards
René

3

Okay, got it…

I added the following line to the playbook I posted above (within the ec2 block):

user_data: "{{ my_user_data }}"

After that I created this block in my variable file:

`

hostname: “test1234”
fqdn: “test1234.example.local”
my_user_data: |
#cloud-config
hostname: “{{ hostname }}”
fqdn: “{{ fqdn }}”

`