dhcpd.conf template does not render

[ahgraber]

I'm working through your netboot solution, and I have an interesting issue where dhcpd.conf.j2 does not render properly (no variables are substituted). All of the other templates work just fine, and the variables used in dhcpd.conf.j2 are available if I run a debug step:

# all variables are present with correct values
- debug:
    var: '{{item}}'
  with_items:
    - ansible_default_ipv4.address
    - ansible_default_ipv4.broadcast
    - ansible_default_ipv4.gateway
    - ansible_default_ipv4.netmask
    - ansible_default_ipv4.network

# no substitution occurs
- name: Render DHCP config
  template:
    src: dhcpd.conf.j2
    dest: "{{ role_path }}/files/dhcp/dhcpd.conf"
    mode: 0644

# substitution occurs correctly
- name: Render GRUB config
  template:
    src: grub.cfg.j2
    dest: "{{ role_path }}/files/data/boot/grub/grub.cfg"
    mode: 0644

Do you have any thoughts?

[khuedoan]

What is the path of your DHCP config file, is it metal/roles/pxe_server/files/data/pxe-config/dhcpd.conf, can you post the full file in that path?

Also can you post a link to your code, I don't see it on your profile.

[ahgraber]

Full path is as you expected metal/roles/pxe_server/files/data/pxe-config/dhcpd.conf

Hadn't pushed my code previously as I was just trying to get it to work. Just pushed to metal branch

A bit more background -- previously I had been trying to run this on an Ubuntu VM I'm using as a jump box so it's in the same subnet as my lab. The dhcpd.conf does not render on the VM. However, if I try on my local machine, it does render correctly. It's weird because the grub.cfg template works fine on the VM.
Is there a dependency I might be missing on the VM?

dhcpd.conf with missing substitutions:

subnet {{ ansible_default_ipv4.network }} netmask {{ ansible_default_ipv4.netmask }} {
    option routers {{ ansible_default_ipv4.gateway }};
    range {{ ansible_default_ipv4.network | ansible.netcommon.ipmath(1) }} {{ ansible_default_ipv4.broadcast | ansible.netcommon.ipmath(-1) }};

    class "pxeclients" {
        match if substring (option vendor-class-identifier, 0, 9) = "PXEClient";
        next-server {{ ansible_default_ipv4.address }};

        if option architecture-type = 00:07 {
            filename "grubx64.efi";
        }
    }
}

grub.cfg with successful substitutions:

menuentry 'ubuntu-20.04.3-live-server-amd64 (autoinstall)' --id=autoinstall {
    echo "Loading Kernel..."
    linux vmlinuz \
        ip=dhcp \
        url=http://10.2.1.100/iso/ubuntu-20.04.3-live-server-amd64.iso autoinstall \
        ds="nocloud-net;seedfrom=http://10.2.1.100/" root=/dev/ram0 cloud-config-url=/dev/null
    echo "Loading Ram Disk..."
    initrd initrd
}

[khuedoan]

Does running the playbook with -vvv show any other related info?

[khuedoan]

It also renders fine on my machine.

[ahgraber]

Does running the playbook with -vvv show any other related info?

Not really. I compared the task for dhcpd.conf to the task for grub.cfg and the logs look pretty much identical aside from the different paths.

[khuedoan]

run this on an Ubuntu VM I'm using as a jump box

Is it a clean VM? I can't replicate the issue so the VM might be the problem.

[ahgraber]

Is it a clean VM?

That's a fair point. I can definitely try a different one.

A side question --
My lab subnet is 10.2.0.0/16. I have my router set up as a DHCP server for the subnet, but only service addresses in range 10.2.1.100 - 10.2.1.200.
Will running the additional dhcp server for a different IP range (10.2.118.0/24) in the lab subnet cause problems? If so, how would you advise setting things up?

Thanks for your time!

[khuedoan]

The current setup is tested on a flat 192.168.1.0/24 network, which is the most common case, but you can always customize the parameters of the DHCP config if needed. If you worry about the DHCP server you can add a handler for Ansible to turn off the PXE server after the machines are booted (in my case the IP range is the same with my router so it doesn't matter much)

[khuedoan]

Seem like you got it working ahgraber/homelab-infra@426ff06, closing.