| `build-tool` / `DOCKER_BUILD_TOOL` | The build tool to use for building container image, possible values are `kaniko`, `buildah`, `dind` or`external` |`$TBC_DEFAULT_DOCKER_BUILD_TOOL`(defaults to `buildah`) |
| `build-tool` / `DOCKER_BUILD_TOOL` | The build tool to use for building container image, possible values are `kaniko`, `buildah`, `dind`,`external`or `default`| `default` uses`$TBC_DEFAULT_DOCKER_BUILD_TOOL`value (`buildah` by default) |
| `kaniko-image` / `DOCKER_KANIKO_IMAGE` | The image used to run `kaniko` - _for kaniko build only_ | `gcr.io/kaniko-project/executor:debug` (use `debug` images for GitLab)<br/>[](https://to-be-continuous.gitlab.io/doc/secu/trivy-DOCKER_KANIKO_IMAGE)|
| `buildah-image` / `DOCKER_BUILDAH_IMAGE` | The image used to run `buildah` - _for buildah build only_ | `quay.io/containers/buildah:latest`<br/>[](https://to-be-continuous.gitlab.io/doc/secu/trivy-DOCKER_BUILDAH_IMAGE)|
| `image` / `DOCKER_IMAGE` | The Docker image used to run the docker client (see [full list](https://hub.docker.com/r/library/docker/)) - _for Docker-in-Docker build only_ | `docker.io/library/docker:latest`<br/>[](https://to-be-continuous.gitlab.io/doc/secu/trivy-DOCKER_IMAGE) |