Install Ubuntu Server With Autoinstall

Alvinditya Saputra included in Documentation

2026-08-07 726 words 4 minutes

Contents

Overview & Core Concepts

TL;DR. This guide explains how to automate the installation of Ubuntu Server 24.04 LTS (Unattended Autoinstall) using the auto_install plugin from Ventoy and Cloud-Init (Subiquity). With this method, the OS installation on Mini PCs / Bare-metal Servers can run automatically from start to finish without manual interaction.

Scope / Domain: Automated Server Provisioning, Unattended OS Installation, Homelab / Bare-metal Setup.
Tech Stack Related: Ubuntu Server 24.04 LTS, Ventoy Auto Install Plugin, Cloud-Init / Subiquity (user-data & meta-data), OpenSSL, LVM.
Target Use Case: Automated local server / Mini PC setup via USB Flash Drive without the need to manually enter hostname, username, password, or network configurations during the boot process.

Setup & Initial Configuration

1. Ventoy Flash Drive Folder Structure

Place the Ubuntu Server ISO and the autoinstall configuration folders on the root of a Ventoy-installed USB Flash Drive with the following structure:

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/ (Ventoy Flash Drive Root)
├── ubuntu-24.04-live-server-amd64.iso  <-- Ubuntu Server ISO file
└── ubuntu/
    ├── autoinstall/
    │   ├── meta-data                   <-- Initial instance/hostname identity
    │   └── user-data                   <-- Cloud-config & installation automation script
    └── ventoy/
        └── ventoy.json                 <-- ISO mapping to autoinstall script

2. Generating Encrypted Password (SHA-512)

By default, user-data requires a password in SHA-512 hash format. Run the following command in a Linux/macOS terminal to generate the password hash:

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openssl passwd -6 "YourStrongPassword"

Output Result: $6$xxxxxx$... (Copy this hash string into the identity.password field in user-data).

Usage & Code Snippets

1. Mapping Configuration File: `ventoy.json`

Location: /ubuntu/ventoy/ventoy.json

This file tells Ventoy to automatically load the user-data template when the Ubuntu Server ISO is selected.

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{
  "auto_install": [
    {
      "image": "/ubuntu-24.04-live-server-amd64.iso",
      "template": "/ubuntu/autoinstall/user-data"
    }
  ]
}

2. Instance Metadata File: `meta-data`

Location: /ubuntu/autoinstall/meta-data

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instance-id: ubuntu-autoinstall
local-hostname: changeme

3. Autoinstall Main Config File: `user-data`

Location: /ubuntu/autoinstall/user-data

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#cloud-config
autoinstall:
  version: 1

  apt:
    geoip: true
    preserve_sources_list: false
    primary:
    - arches: [ amd64, i386 ]
      uri: http://archive.ubuntu.com/ubuntu
    - arches: [ default ]
      uri: http://ports.ubuntu.com/ubuntu-ports

  identity:
    hostname: changeme
    realname: Changeme
    username: changeme
    password: changeme # Replace with output from: openssl passwd -6 "YourStrongPassword"

  ssh:
    install-server: true
    allow-pw: true
    authorized-keys: []

  keyboard:
    layout: us

  locale: en_US

  storage:
    layout:
      name: lvm
      sizing-policy: all

  network:
    version: 2
    ethernets:
      enp0s31f6:
        dhcp4: true

    wifis:
      wlp3s0:
        dhcp4: true
        access-points:
          "Your WiFi SSID":
            password: "yourwifipassword"

  packages:
  - curl

  late-commands:
  - curtin in-target -- apt update
  - curtin in-target -- systemctl enable ssh

Troubleshooting & Known Issues

Problem / Error	Cause	Solution / Workaround
LVM disk capacity truncated (only ~100GB)	By default, the Ubuntu Subiquity installer with `storage.layout.name: lvm` only allocates a max of 100 GB for the Logical Volume (`ubuntu-lv`), while the rest of the disk is left unallocated.	Run the following commands on the server after installation completes to extend the LV to the remaining disk space: `sudo lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv` `sudo resize2fs /dev/ubuntu-vg/ubuntu-lv`
Network Connection / Interface Not Detected	Network interface names in `user-data` (`enp0s31f6` / `wlp3s0`) are hardcoded and might differ on each PC hardware.	Adjust the ethernet/Wi-Fi interface names according to the target device, or use generic DHCP/netplan configuration after the OS is installed.
SSH Login Failed with Password Hash	Entering plain-text password directly into the `identity.password` field without OpenSSL encryption.	Always generate a SHA-512 hash using `openssl passwd -6 "YourPassword"` before inserting it into `user-data`.
Ventoy Does Not Automatically Load Autoinstall	The ISO or template path in `ventoy.json` does not match the physical location on the USB Flash Drive.	Ensure the ISO and `user-data` template file locations in `ventoy.json` start with a slash `/` from the flash drive root.

Best Practices & Pitfalls

Do:
- Use openssl passwd -6 to encrypt user passwords before saving user-data.
- Perform LVM disk expansion (lvextend) post-installation if using disk capacity > 100GB.
- Verify network interface name compatibility (Ethernet / Wi-Fi) on target hardware.
Don’t:
- Save plain-text passwords in the user-data file.
- Change the ventoy.json folder location from the default path /ventoy/ventoy.json or /ubuntu/ventoy/ventoy.json.