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Creating a Custom Rocky Linux ISO

createcustomISORocky Linux

Howard Van Der Wal
Customer Support Engineer

Introduction

Customers often need a custom ISO for a litany of reasons - perhaps they require a mirror of a repository or to edit kernel cmdline parameters for their own customers.

Problem

This guide was created after a customer raised a question in #1629 - creating a custom installation ISO, asking for assistance on how to create a Rocky Linux 8.10 ISO.

Symptoms

The customer did not have clear direction or resources on how to build their own ISO.

Resolution

  • The customer was given multiple documentation sources to reference, a high level ISO generation guide and multiple commands to execute.
  • A guide on how to create a custom Rocky Linux ISO was also pushed upstream to the Rocky Linux Docs. Please find the same guide below:

Prerequisites

  • A 64 bit machine running Rocky Linux 9 to build the new ISO image.
  • A Rocky Linux 9 DVD ISO image.
  • A kickstart file to apply to the ISO.
  • Read the Lorax Quickstart and mkksiso documentation to become familiar with how the Anaconda boot.iso is created.

Package installation and setup

  • Install the lorax package:
sudo dnf install -y lorax

Building the ISO with a kickstart file

  • Run the mkksiso command to add a kickstart file and then build a new ISO:
mkksiso --ks <PATH_TO_KICKSTART_FILE> <PATH_TO_ISO_TO_MODIFY> <OUTPUT_PATH_FOR_BUILT_ISO>
  • Below is an example kickstart file example-ks.cfg, which sets up a Rocky Linux 9.5 Server With GUI environment:
lang en_GB
keyboard --xlayouts='us'
timezone Asia/Tokyo --utc
reboot
cdrom
bootloader --append="rhgb quiet crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M"
zerombr
clearpart --all --initlabel
autopart
network --bootproto=dhcp
firstboot --disable
selinux --enforcing
firewall --enabled
%packages
@^server-product-environment
%end

Adding a repository with its packages to an ISO image

  • Make sure the repository you want to add has the repodata directory inside of it. If not, this can be created using the createrepo_c command and this can be installed with sudo dnf install -y createrepo_c
  • Add the repository to your kickstart file, using the following syntax:
repo --name=extra-repo --baseurl=file:///run/install/repo/<YOUR_REPOSITORY>/
  • Add your repository using the --add flag with the mkksiso tool:
mkksiso --add <LINK_TO_YOUR_REPOSITORY> --ks <PATH_TO_KICKSTART_FILE> <PATH_TO_ISO_TO_MODIFY> <OUTPUT_PATH_FOR_BUILT_ISO>
  • The process is detailed further using the baseos repository in the example below:
  • The base os repository will be locally downloaded along with all of its packages:
dnf reposync -p ~ --download-metadata --repo=baseos
  • Then add the repository to the kickstart file:
repo --name=extra-repo --baseurl=file:///run/install/repo/baseos/
  • The kickstart file would look like the following:
lang en_GB
keyboard --xlayouts='us'
timezone Asia/Tokyo --utc
reboot
cdrom
bootloader --append="rhgb quiet crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M"
zerombr
clearpart --all --initlabel
autopart
network --bootproto=dhcp
firstboot --disable
selinux --enforcing
firewall --enabled
%packages
@^server-product-environment
repo --name=extra-repo --baseurl=file:///run/install/repo/baseos/
%end
  • Then point the mkkiso command directly to the repository directory and build the ISO:
mkksiso --add ~/baseos --ks example-ks.cfg ~/Rocky-9.5-x86_64-dvd.iso ~/Rocky-9.5-x86_64-dvd-new.iso

Conclusion

What has been discussed here are just a few of the options available to tweak and build your own Rocky Linux ISO. For further ways, including modifying the kernel cmdline arguments, the author highly recommends to go through the mkksiso documentation in more detail.

References & related articles

Anaconda Documentation
Automating the Installation with Kickstart - Fedora Wiki
Dracut - Fedora Wiki
Lorax Documentation
mkksiso Documentation
Mock Repository
Peridot Repository