Add Packer template for building Ubuntu 24.04 server image

Build a QCOW2 image locally with QEMU/KVM + autoinstall, then provision
with the existing Ansible playbook. Allows testing changes locally before
deploying to production. Outputs a ready-to-upload image for hosting providers.

Usage: cp server.pkrvars.hcl.example server.pkrvars.hcl, fill in values,
then run ./build.sh

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packer/.gitignore

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+output/
+server.pkrvars.hcl
+packer_cache/

packer/build.sh

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+#!/bin/bash
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+if [ ! -f server.pkrvars.hcl ]; then
+    echo "Error: server.pkrvars.hcl not found."
+    echo "Copy server.pkrvars.hcl.example to server.pkrvars.hcl and fill in your values."
+    exit 1
+fi
+
+echo "=== Initializing Packer plugins ==="
+packer init ubuntu-server.pkr.hcl
+
+echo ""
+echo "=== Building image ==="
+echo "This will take 15-30 minutes depending on your machine."
+echo ""
+
+packer build -var-file=server.pkrvars.hcl ubuntu-server.pkr.hcl
+
+echo ""
+echo "==========================================="
+echo "  Image built successfully!"
+echo "==========================================="
+echo "  Output: $SCRIPT_DIR/output/packer-ubuntu-server"
+echo ""
+echo "  To test locally:"
+echo "    qemu-system-x86_64 -m 4096 -hda output/packer-ubuntu-server -enable-kvm"
+echo ""
+echo "  To convert for other formats:"
+echo "    qemu-img convert -f qcow2 -O raw output/packer-ubuntu-server output/server.raw"
+echo "    qemu-img convert -f qcow2 -O vmdk output/packer-ubuntu-server output/server.vmdk"
+echo "==========================================="

packer/http/user-data

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+#cloud-config
+autoinstall:
+  version: 1
+  locale: en_US.UTF-8
+  keyboard:
+    layout: us
+  network:
+    version: 2
+    ethernets:
+      id0:
+        match:
+          driver: virtio_net
+        dhcp4: true
+  storage:
+    layout:
+      name: lvm
+      sizing-policy: all
+  identity:
+    hostname: server
+    username: ubuntu
+    password: "$6$XjqGOA0giVyHdSZ0$9YqNQlsfuU5xo8uLqpnD49mS3KqyMSp.6imNnIQE18obgTyE0g8LOcL6hvg0sJQXgHv6S7HSIBpKY0.keMXKU."
+  ssh:
+    install-server: true
+    allow-pw: true
+  packages:
+    - openssh-server
+    - curl
+    - wget
+  late-commands:
+    - "echo 'ubuntu ALL=(ALL) NOPASSWD:ALL' > /target/etc/sudoers.d/ubuntu"
+    - "chmod 440 /target/etc/sudoers.d/ubuntu"

packer/server.pkrvars.hcl.example

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+base_domain           = "example.com"
+ssh_pubkey            = "ssh-ed25519 AAAA... user@host"
+juicefs_s3_endpoint   = "https://s3.amazonaws.com"
+juicefs_s3_bucket     = "my-nextcloud-bucket"
+juicefs_s3_access_key = "AKIAIOSFODNN7EXAMPLE"
+juicefs_s3_secret_key = "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"
+juicefs_cache_size    = "50G"

packer/ubuntu-server.pkr.hcl

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+packer {
+  required_plugins {
+    qemu = {
+      version = "~> 1"
+      source  = "github.com/hashicorp/qemu"
+    }
+    ansible = {
+      version = ">= 1.1.2"
+      source  = "github.com/hashicorp/ansible"
+    }
+  }
+}
+
+# --- VM settings ---
+
+variable "cpu" {
+  type    = string
+  default = "2"
+}
+
+variable "ram" {
+  type    = string
+  default = "4096"
+}
+
+variable "disk_size" {
+  type    = string
+  default = "50000"
+}
+
+variable "headless" {
+  type    = bool
+  default = true
+}
+
+# --- Ubuntu ISO ---
+
+variable "iso_url" {
+  type    = string
+  default = "https://releases.ubuntu.com/24.04/ubuntu-24.04.2-live-server-amd64.iso"
+}
+
+variable "iso_checksum" {
+  type    = string
+  default = "file:https://releases.ubuntu.com/24.04/SHA256SUMS"
+}
+
+# --- OS user (created by autoinstall) ---
+
+variable "ssh_username" {
+  type    = string
+  default = "ubuntu"
+}
+
+variable "ssh_password" {
+  type      = string
+  default   = "ubuntu"
+  sensitive = true
+}
+
+# --- Server config (passed to Ansible) ---
+
+variable "base_domain" {
+  type = string
+}
+
+variable "ssh_pubkey" {
+  type    = string
+  default = ""
+}
+
+variable "juicefs_s3_endpoint" {
+  type = string
+}
+
+variable "juicefs_s3_bucket" {
+  type = string
+}
+
+variable "juicefs_s3_access_key" {
+  type      = string
+  sensitive = true
+}
+
+variable "juicefs_s3_secret_key" {
+  type      = string
+  sensitive = true
+}
+
+variable "juicefs_cache_size" {
+  type    = string
+  default = "50G"
+}
+
+source "qemu" "ubuntu-server" {
+  accelerator  = "kvm"
+  boot_command = [
+    "c<wait>",
+    "linux /casper/vmlinuz --- autoinstall ds=\"nocloud;s=http://{{ .HTTPIP }}:{{ .HTTPPort }}/\"<enter><wait>",
+    "initrd /casper/initrd<enter><wait>",
+    "boot<enter><wait>"
+  ]
+  boot_wait        = "10s"
+  disk_cache       = "none"
+  disk_compression = true
+  disk_discard     = "unmap"
+  disk_interface   = "virtio"
+  disk_size        = var.disk_size
+  format           = "qcow2"
+  headless         = var.headless
+  http_directory   = "http"
+  iso_checksum     = var.iso_checksum
+  iso_url          = var.iso_url
+  net_device       = "virtio-net"
+  output_directory = "output"
+  qemu_binary      = "/usr/bin/qemu-system-x86_64"
+  qemuargs = [
+    ["-m", "${var.ram}M"],
+    ["-smp", var.cpu],
+    ["-cpu", "host"]
+  ]
+  shutdown_command      = "echo '${var.ssh_password}' | sudo -S shutdown -P now"
+  ssh_password          = var.ssh_password
+  ssh_username          = var.ssh_username
+  ssh_handshake_attempts = 500
+  ssh_timeout           = "45m"
+  ssh_wait_timeout      = "45m"
+}
+
+build {
+  sources = ["source.qemu.ubuntu-server"]
+
+  provisioner "shell" {
+    execute_command = "echo '${var.ssh_password}' | sudo -S bash -c '{{ .Vars }} {{ .Path }}'"
+    inline = [
+      "apt-get update",
+      "apt-get install -y ansible-core python3-pip"
+    ]
+  }
+
+  provisioner "file" {
+    source      = "../playbook.yml"
+    destination = "/tmp/playbook.yml"
+  }
+
+  provisioner "file" {
+    source      = "../resources"
+    destination = "/tmp/resources"
+  }
+
+  provisioner "shell" {
+    execute_command = "echo '${var.ssh_password}' | sudo -S bash -c '{{ .Vars }} {{ .Path }}'"
+    environment_vars = [
+      "ANSIBLE_FORCE_COLOR=1"
+    ]
+    inline = [
+      "ansible-playbook -i localhost, -c local /tmp/playbook.yml -e 'base_domain=${var.base_domain} ssh_pubkey=\"${var.ssh_pubkey}\" juicefs_s3_endpoint=${var.juicefs_s3_endpoint} juicefs_s3_bucket=${var.juicefs_s3_bucket} juicefs_s3_access_key=${var.juicefs_s3_access_key} juicefs_s3_secret_key=${var.juicefs_s3_secret_key} juicefs_cache_size=${var.juicefs_cache_size}'"
+    ]
+  }
+
+  provisioner "shell" {
+    execute_command = "echo '${var.ssh_password}' | sudo -S bash -c '{{ .Vars }} {{ .Path }}'"
+    inline = [
+      "rm -rf /tmp/playbook.yml /tmp/resources",
+      "apt-get clean",
+      "rm -rf /var/lib/apt/lists/*",
+      "cloud-init clean --logs",
+      "truncate -s 0 /etc/machine-id",
+      "rm -f /var/lib/dbus/machine-id",
+      "fstrim -av || true"
+    ]
+  }
+}