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Creating a Custom Rocky Linux ISO

Introduction

You might need to create a custom ISO for many reasons. Perhaps you want to change the boot process, add specific packages, or update a configuration file.

This guide will instruct you from start to finish on how to build your own Rocky Linux ISO.

Prerequisites

  • A 64-bit machine running Rocky Linux 9
  • 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 to create the Anaconda boot.iso.

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, you can create this using the createrepo_c command and install it 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>
  • You can see additional details of this process 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 mkksiso 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

I'm sharing a few options to tweak and build your Rocky Linux ISO here. For further ways, including modifying the kernel cmdline arguments, the author highly recommends going through the mkksiso documentation in more detail.

Author: Howard Van Der Wal

Contributors: Steven Spencer, Ganna Zhyrnova