Current Ubuntu Server installer
The current Ubuntu Server installer features:
Support for all Ubuntu Server architectures:
- x86-64, ARM v7, ARM64, POWER9/POWER10, IBM zSystems and LinuxONE (s390x), RISC-V
PXE and HTTP boot
SSH based install
Offline and network-gapped install (serial console)
Autoinstall (unattended mode)
RAID, LVM, LUKS support and several filesystem configurations
Installation guides are available for using the new installer on various architectures, including for netboot scenarios. Get help migrating to the current Ubuntu Server installer on Ubuntu Discourse!
This installer is based on the Subiquity installer software. It was previously referred to as "server live installer". It uses curtin for disk partitioning. On the installation target, cloud-init handles the initial network configuration.
Status of the Minimal ISO image
Ubuntu 18.04 LTS was the last Ubuntu release which "mini.iso" images were produced for. These images, which Canonical and the Ubuntu project never officially supported, were always limited to BIOS booting on the amd64 and i386 platforms only. They existed as a by-product of building the old server installer (based on "debian-installer"; later called "alternative installer").
Ubuntu 18.04 LTS mini.iso:
For reference: The old mini.iso
Introduction
The minimal iso image will download packages from online archives at installation time instead of providing them on the install media itself. Downloading packages at install time reduces the size of the iso image to approximately ~40MB depending on architecture (see below), as well as providing only the packages needed for installation. The download time savings achieved by using a mini iso can be significant, as only current packages are downloaded, so there is no need to upgrade packages immediately after installation. The mini iso uses a text-based installer, making the image as compact as possible.
To use the mini iso image download mini.iso from one of the following links and burn it to a CD or USB drive.
For help with CD burning, see BurningIsoHowto
For help with USB drive burning, see Installation/FromUSBStick
For differences between Ubuntu release versions, please see Releases.
To install, boot your computer from the the mini iso and select "Install" at the prompt. You can then follow the instructions from the text-based installer. On the software selection screen, you can select from a number of collections of software such as different desktop environments (kde, xfce, etc), a multitude of different servers, multimedia creation tools, media center (mythbuntu), etc. You can also select "Manual package selection" which will take you to aptitude. You may also select nothing and just continue to finish the installation. If you selected nothing, upon reboot you will arrive at a cli prompt; from here you can fully customize your new system.
UEFI mode
While the minimal iso image is handy, it isn't useful for installing on UEFI-based systems that you want to run in UEFI mode. The mini iso lacks the proper files for booting the computer in UEFI mode. Thus, the computer will boot in BIOS compatibility mode, and the installation will be in BIOS mode.
You can use an Ubuntu Server amd64 iso file (64-bit) for 'mini installations' in UEFI mode. There is a compressed image file dd_text_16.04-UEFI-n-BIOS-4-pendrive-7.8GB.img.xz of such an installed system, that can be used as a start of a custom installation.
See this link: Installation/UEFI-and-BIOS/stable-alternative.
64-bit PC (amd64, x86_64) (Recommended)
Ubuntu 18.04 "Bionic Beaver" 64MB (MD5: 8388f7232b400bdc80279668847f90da, SHA1: cce936c1f9d1448c7d8f74b76b66f42eb4f93d4a)
32-bit PC (i386, x86)
Ubuntu 18.04 "Bionic Beaver" 57MB (MD5: c7b21dea4d2ea037c3d97d5dac19af99, SHA1: a2a3b9c952ffa774ef77974e4e98ed5a9cdba2c8)
General link that seems reliable
This general link has worked for some years, and seems to be kept up to date. It helps you to find and download fully functional official Ubuntu mini.iso files