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---
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stage: Verify
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group: Pipeline Execution
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info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
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type: howto
---
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# Use kaniko to build Docker images **(FREE)**
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> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/45512) in GitLab 11.2. Requires GitLab Runner 11.2 and above.
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[kaniko ](https://github.com/GoogleContainerTools/kaniko ) is a tool to build
container images from a Dockerfile, inside a container or Kubernetes cluster.
kaniko solves two problems with using the
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[Docker-in-Docker build ](using_docker_build.md#use-the-docker-executor-with-the-docker-image-docker-in-docker )
method:
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- Docker-in-Docker requires [privileged mode ](https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities )
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to function, which is a significant security concern.
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- Docker-in-Docker generally incurs a performance penalty and can be quite slow.
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## Requirements
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To use kaniko with GitLab, [a runner ](https://docs.gitlab.com/runner/ ) with one
of the following executors is required:
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- [Kubernetes ](https://docs.gitlab.com/runner/executors/kubernetes.html ).
- [Docker ](https://docs.gitlab.com/runner/executors/docker.html ).
- [Docker Machine ](https://docs.gitlab.com/runner/executors/docker_machine.html ).
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## Building a Docker image with kaniko
When building an image with kaniko and GitLab CI/CD, you should be aware of a
few important details:
- The kaniko debug image is recommended (`gcr.io/kaniko-project/executor:debug`)
because it has a shell, and a shell is required for an image to be used with
GitLab CI/CD.
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- The entrypoint needs to be [overridden ](using_docker_images.md#overriding-the-entrypoint-of-an-image ),
otherwise the build script doesn't run.
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- A Docker `config.json` file needs to be created with the authentication
information for the desired container registry.
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In the following example, kaniko is used to:
1. Build a Docker image.
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1. Then push it to [GitLab Container Registry ](../../user/packages/container_registry/index.md ).
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The job runs only when a tag is pushed. A `config.json` file is created under
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`/kaniko/.docker` with the needed GitLab Container Registry credentials taken from the
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[predefined CI/CD variables ](../variables/index.md#predefined-cicd-variables )
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GitLab CI/CD provides.
In the last step, kaniko uses the `Dockerfile` under the
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root directory of the project, builds the Docker image and pushes it to the
project's Container Registry while tagging it with the Git tag:
```yaml
build:
stage: build
image:
name: gcr.io/kaniko-project/executor:debug
entrypoint: [""]
script:
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- mkdir -p /kaniko/.docker
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- echo "{\"auths\":{\"$CI_REGISTRY\":{\"auth\":\"$(echo -n ${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD} | base64 | tr -d '\n')\"}}}" > /kaniko/.docker/config.json
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- /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_TAG
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rules:
- if: $CI_COMMIT_TAG
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```
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### Building an image with kaniko behind a proxy
If you use a custom GitLab Runner behind an http(s) proxy, kaniko needs to be set
up accordingly. This means:
- Adding the proxy to `/kaniko/.docker/config.json`
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- Passing the `http_proxy` environment variables as build arguments so the Dockerfile
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instructions can use the proxy when building the image.
The previous example can be extended as follows:
```yaml
build:
stage: build
image:
name: gcr.io/kaniko-project/executor:debug
entrypoint: [""]
script:
- mkdir -p /kaniko/.docker
- |-
KANIKOPROXYBUILDARGS=""
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KANIKOCFG="{\"auths\":{\"$CI_REGISTRY\":{\"auth\":\"$(echo -n ${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD} | base64 | tr -d '\n')\"}}}"
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if [ "x${http_proxy}" != "x" -o "x${https_proxy}" != "x" ]; then
KANIKOCFG="${KANIKOCFG}, \"proxies\": { \"default\": { \"httpProxy\": \"${http_proxy}\", \"httpsProxy\": \"${https_proxy}\", \"noProxy\": \"${no_proxy}\"}}"
KANIKOPROXYBUILDARGS="--build-arg http_proxy=${http_proxy} --build-arg https_proxy=${https_proxy} --build-arg no_proxy=${no_proxy}"
fi
KANIKOCFG="${KANIKOCFG} }"
echo "${KANIKOCFG}" > /kaniko/.docker/config.json
- /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile $KANIKOPROXYBUILDARGS --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_TAG
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rules:
- if: $CI_COMMIT_TAG
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```
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## Using a registry with a custom certificate
When trying to push to a Docker registry that uses a certificate that is signed
by a custom CA, you might get the following error:
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```shell
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$ /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --no-push
INFO[0000] Downloading base image registry.gitlab.example.com/group/docker-image
error building image: getting stage builder for stage 0: Get https://registry.gitlab.example.com/v2/: x509: certificate signed by unknown authority
```
This can be solved by adding your CA's certificate to the kaniko certificate
store:
```yaml
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before_script:
- mkdir -p /kaniko/.docker
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- echo "{\"auths\":{\"$CI_REGISTRY\":{\"auth\":\"$(echo -n ${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD} | base64 | tr -d '\n')\"}}}" > /kaniko/.docker/config.json
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- |
echo "-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----" >> /kaniko/ssl/certs/additional-ca-cert-bundle.crt
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```
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## Video walkthrough of a working example
The [Least Privilege Container Builds with Kaniko on GitLab ](https://www.youtube.com/watch?v=d96ybcELpFs )
video is a walkthrough of the [Kaniko Docker Build ](https://gitlab.com/guided-explorations/containers/kaniko-docker-build )
Guided Exploration project pipeline. It was tested on:
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- [GitLab.com shared runners ](../runners/index.md )
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- [The Kubernetes runner executor ](https://docs.gitlab.com/runner/executors/kubernetes.html )
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The example can be copied to your own group or instance for testing. More details
on what other GitLab CI patterns are demonstrated are available at the project page.
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## Troubleshooting
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### 403 error: "error checking push permissions"
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If you receive this error, it might be due to an outside proxy. Setting the `http_proxy`
and `https_proxy` [environment variables ](../../administration/packages/container_registry.md#running-the-docker-daemon-with-a-proxy )
can fix the problem.