HomeLab – Building a Solid Linux Foundation (Kubuntu 25 + VMware + Ansible) – Day 1

Goal: prepare the host (Kubuntu 25), create a reusable base VM template (Ubuntu Server 24.04), clone a k3s-master VM, and verify connectivity with Ansible.

Host context we’ll use throughout this series: hostname fullstacklab.site, user stackadmin

Why this matters (short theory)

Before touching Kubernetes or SIEM, you need a repeatable lab you can destroy and rebuild in minutes. Today we set up:

• a clean host with admin tools,
• a base VM template with SSH and correct networking,
• a clone workflow (Snapshot → Full Clone),
• and a first Ansible ping to prove remote automation works.

Topology at a glance

Step 0 — Prepare the host (Kubuntu 25)

Run these once on your host:

sudo hostnamectl set-hostname fullstacklab.site
sudo apt update
sudo apt install -y openssh-client ansible curl jq git make python3-pip tree net-tools docker.io
sudo usermod -aG docker stackadmin

# SSH key for user 'stackadmin' if you don't have one yet:
sudo -u stackadmin bash -lc 'test -f ~/.ssh/id_ed25519 || ssh-keygen -t ed25519 -C "stackadmin@fullstacklab.site" -N "" -f ~/.ssh/id_ed25519'

Note: Docker is for later (Minikube and CI). The important bits today are SSH and Ansible.

Step 1 — VMware networking (Host-only + NAT)

• vmnet1 (Host-only): 192.168.56.0/24, DHCP OFF
• vmnet8 (NAT): DHCP ON (Internet egress only)

Use Virtual Network Editor (as root) to confirm these settings.

Step 2 — Create the Base Template VM (Ubuntu 24.04)

1. New VM (EFI, 20 GB thin, 2 vCPU, 2 GB RAM) with two NICs:
   • ens33 → vmnet1 (Host-only)
   • ens34 → vmnet8 (NAT)
2. Install Ubuntu Server 24.04 (minimal) and OpenSSH server. Create user stackadmin with sudo.
3. Configure Netplan for static IP on vmnet1:

# /etc/netplan/01-lab.yaml
network:
  version: 2
  ethernets:
    ens33:   # vmnet1 (Host-only)
      addresses: [192.168.56.10/24]
    ens34:   # vmnet8 (NAT)
      dhcp4: true

Apply & verify:

sudo netplan apply
ip -br addr

4. Add your public key to the VM (on the VM):

mkdir -p ~/.ssh && chmod 700 ~/.ssh
echo "<your_public_key_here>" >> ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

5. Test from the host:

ssh stackadmin@192.168.56.10 'hostnamectl; ip -br addr'

6. Shut down the VM and create a snapshot named gold.

Use a Full Clone from the gold snapshot and boot it. Then set the hostname:

sudo hostnamectl set-hostname k3s-master

Step 4 — First Ansible “ping”

Edit your inventory (example assumes 192.168.56.10):

# ansible/inventory/hosts.ini
[k3s_master]
k3s-master ansible_host=192.168.56.10 ansible_user=stackadmin

[all:vars]
ansible_become=true

Then:

# Without sudo (quickest test)
ansible -i ansible/inventory/hosts.ini k3s_master -m ping -e 'ansible_become=false'

# Or with sudo prompt when needed:
ansible -i ansible/inventory/hosts.ini k3s_master -m ping -b -K

If you prefer zero-prompt sudo in the lab, on the VM:

echo 'stackadmin ALL=(ALL) NOPASSWD:ALL' | sudo tee /etc/sudoers.d/90-stackadmin-nopasswd >/dev/null
sudo chmod 0440 /etc/sudoers.d/90-stackadmin-nopasswd
sudo visudo -cf /etc/sudoers.d/90-stackadmin-nopasswd

Troubleshooting (teach yourself to prove root cause)

• SSH auth fails? Check ~/.ssh/authorized_keys (600), sshd status (systemctl status ssh), firewall (sudo nft list ruleset).
• Wrong NIC names? ip -br link and adjust Netplan interfaces.
• No route to Internet? Make sure ens34 (vmnet8) is DHCP.
• Ansible complains about host key? SSH once interactively to accept the fingerprint, or pass -e 'ansible_ssh_common_args="-o StrictHostKeyChecking=no"'.

What you learned today (beginner-friendly recap)

• The host isn’t your lab; it’s your control plane (Ansible, SSH key, tooling).
• A Base Template + Snapshot saves hours—clones are cheap, reproducible, and safe.
• A successful Ansible ping proves the “remote automation path” is alive.