this is going to be my personal experience of making custom ublue image. hopefully you will learn something from it.

so first of all you have to decide which Desktop Environment you want to use. I have chosen KDE but you can choose whichever DE you want. to see available DE you can go here. now copy the url of the image you want to modify. for my case it will be ghcr.io/ublue-os/kinoite-main:39.

create a file and name it Dockerfile. and add the following line to the Dockerfile

FROM ghcr.io/ublue-os/kinoite-main:39
# Install your favoutie program using rpm-ostree
RUN rpm-ostree install zsh fish neovim vim emacs kitty alacritty distrobox -y
# finally cleanup and commit the changes
RUN rpm-ostree cleanup -m && \
ostree container commit

save the file and run the following command in the current directory to build the image. (make sure you have docker installed on your system)

sudo docker build -t custom_image:latest .

you can now upload it to ghcr.io or rebase on it using rpm-ostree rebase command.

I hope this was useful. :)