Ubuntu 22.04 reinstallation without a screen

Question

I have an Ubuntu server at home to use as a workplace storage, etc. and I need to reinstall it. I don't have a monitor to do it because I don't have the right plug, they aren't selling them in my location, and I can't get them online. Is there a way to reinstall Ubuntu Server 22.04 without a screen?

Answer 1

The Ubuntu Server installer for 20.04 and later supports a new mode of operation: automated installation, autoinstallation for short. You might also know this feature as unattended or hands off or legacy preseeded installation.

Autoinstallation lets you answer all those configuration questions ahead of time with an autoinstall config and lets the installation process run without any interaction.

Providing the autoinstall config

The autoinstall config is provided via cloud-init configuration, which is almost endlessly flexible. In most scenarios the easiest way will be to provide user-data via the nocloud data source.

The autoinstall config should be provided under the autoinstall key in the config. For example:

#cloud-config
autoinstall:
  version: 1
  ...

Running a truly automatic autoinstall

Even if a fully noninteractive autoinstall config is found, the server installer will ask for confirmation before writing to the disks unless autoinstall is present on the kernel command line. This is to make it harder to accidentally create a USB stick that will reformat a machine it is plugged into at boot. Many autoinstalls will be done via netboot, where the kernel command line is controlled by the netboot config – just remember to put autoinstall in there!

Quick start

So you just want to try it out? Well we have the page for you.

Creating an autoinstall config

When any system is installed using the server installer, an autoinstall file for repeating the install is created at /var/log/installer/autoinstall-user-data.

The structure of an autoinstall config

The autoinstall config has full documentation.

Technically speaking the config is not defined as a textual format, but cloud-init config is usually provided as YAML so that is the syntax the documentation uses.

A minimal config is:

version: 1
identity:
    hostname: hostname
    username: username
    password: $crypted_pass

Here is an example file that shows off most features:

version: 1
reporting:
    hook:
        type: webhook
        endpoint: http://example.com/endpoint/path
early-commands:
    - ping -c1 198.162.1.1
locale: en_US
keyboard:
    layout: gb
    variant: dvorak
network:
    network:
        version: 2
        ethernets:
            enp0s25:
               dhcp4: yes
            enp3s0: {}
            enp4s0: {}
        bonds:
            bond0:
                dhcp4: yes
                interfaces:
                    - enp3s0
                    - enp4s0
                parameters:
                    mode: active-backup
                    primary: enp3s0
proxy: http://squid.internal:3128/
apt:
    primary:
        - arches: [default]
          uri: http://repo.internal/
    sources:
        my-ppa.list:
            source: "deb http://ppa.launchpad.net/curtin-dev/test-archive/ubuntu $RELEASE main"
            keyid: B59D 5F15 97A5 04B7 E230  6DCA 0620 BBCF 0368 3F77
storage:
    layout:
        name: lvm
identity:
    hostname: hostname
    username: username
    password: $crypted_pass
ssh:
    install-server: yes
    authorized-keys:
      - $key
    allow-pw: no
snaps:
    - name: go
      channel: 1.14/stable
      classic: true
debconf-selections: |
    bind9      bind9/run-resolvconf    boolean false
packages:
    - libreoffice
    - dns-server^
user-data:
    disable_root: false
late-commands:
    - sed -ie 's/GRUB_TIMEOUT=.*/GRUB_TIMEOUT=30/' /target/etc/default/grub
error-commands:
    - tar c /var/log/installer | nc 192.168.0.1 1000

Many keys and values correspond straightforwardly to questions the installer asks (e.g. keyboard selection). See the reference for details of those that do not.

Error handling

Progress through the installer is reported via the reporting system, including errors. In addition, when a fatal error occurs, the error-commands are executed and the traceback printed to the console. The server then just waits.

_{Source: Automated Server installs | Ubuntu Server Docs}