Creating customized installer images¶

Ubuntu provides both pre-installed images as well as installer images.

The build process of installer images involves multiple steps:

Ubuntu package livecd-rootfs is used to create multiple file system layers as squashfs file systems, e.g.
- livecd.ubuntu-server.ubuntu-server-minimal.squashfs
- livecd.ubuntu-server.ubuntu-server-minimal.ubuntu-server.installer.generic.squashfs
- livecd.ubuntu-server.ubuntu-server-minimal.ubuntu-server.installer.squashfs
- livecd.ubuntu-server.ubuntu-server-minimal.ubuntu-server.squashfs
Ubuntu-cdimage takes these squashfs file systems and packages them as an ISO image.

Patching these tools to create an ISO image is tedious and error-prone.

It is much easier to take an existing live-installer image and to patch it to your needs. Livefs-editor is the tool of choice for this task.

Installing livefs-editor¶

Livefs-editor can be installed in a Python virtual environment with:

git clone https://github.com/mwhudson/livefs-editor.git
cd livefs-editor/
python3 -m venv myvenv
. myvenv/bin/activate
pip install .

For a system-wide installation you can use:

sudo python3 -m pip install --break-system-packages .

Using livefs-editor¶

The livefs-editor README gives an overview of the different actions that the tool can take.

Best practice is to use a yaml file describing all desired actions and to invoke livefs-editor with it:

sudo livefs-editor old.iso new.iso --action-yaml update.yaml

Here is an example yaml file:

---
- name: cp
  source: /home/ubuntu/project/ppa.sources
  dest: $LAYERS[0]/etc/apt/sources.list.d/vendor-ppa.sources
- name: install-packages
  packages:
  - vendor-package1
  - vendor-package2
- name: rm
  path: new/iso/pool/main/e/efivar/libefiboot1_37-6ubuntu2_riscv64.deb
- name: replace-kernel
  flavor: vendorflavor

The cp action sets up the vendor PPA to allow installing vendor specific packages from there.

These are installed by the install-packages action.

With the rm action a package is removed from the ISO.

The replace-kernel action replaces the generic Linux kernel by a vendor kernel package linux-image-vendorflavor located in the vendor PPA with all its dependencies.