To build image for RHEL-7, RHEL-8 need define variables repo_owner, base_image, image_tag, rhel_username, rhel_password and then start build image like

export repo_owner=safarov
export base_image=rhel
export image_tag=8
export rhel_username=${your_username}
export rhel_password=${your_password}
docker build \
    --build-arg base_image=registry.redhat.io/ubi${image_tag} \
    --build-arg image_tag=latest \
    --build-arg rhel_username=${rhel_username} \
    --build-arg rhel_password=${rhel_password} \
    -t ${repo_owner}/kamailio-builder:${base_image}-${image_tag} .

To build image for OpenSUSEneed define variables repo_owner, base_image, image_tag and then start build image like

export repo_owner=safarov
export base_image=opensuse/leap
export image_tag=15
docker build \
    --no-cache \
    --build-arg base_image=${base_image} \
    --build-arg image_tag=${image_tag} \
    --build-arg image_tag=latest \
    -t ${repo_owner}/kamailio-builder:opensuse-${image_tag} .

To build image need to define environement variables repo_owner, base_image, image_tag and then start build image like

export repo_owner=safarov
export base_image=fedora
export image_tag=31
docker build \
    --build-arg base_image=${base_image} \
    --build-arg image_tag=${image_tag} \
    -t ${repo_owner}/kamailio-builder:${base_image}-${image_tag} .

Suported dist

dist	version
rhel	8
rhel	7
centos	8
centos	7
fedora	35
fedora	34
fedora	33
fedora	32
opensuse/leap	15
opensuse/tumbleweed	latest