149 lines
6.2 KiB
Markdown
149 lines
6.2 KiB
Markdown
---
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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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---
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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
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container images from a Dockerfile, inside a container or Kubernetes cluster.
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kaniko solves two problems with using the
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[Docker-in-Docker
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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
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of the following executors is required:
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- [Kubernetes](https://docs.gitlab.com/runner/executors/kubernetes.html).
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- [Docker](https://docs.gitlab.com/runner/executors/docker.html).
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- [Docker Machine](https://docs.gitlab.com/runner/executors/docker_machine.html).
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## Building a Docker image with kaniko
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When building an image with kaniko and GitLab CI/CD, you should be aware of a
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few important details:
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- The kaniko debug image is recommended (`gcr.io/kaniko-project/executor:debug`)
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because it has a shell, and a shell is required for an image to be used with
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GitLab CI/CD.
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- The entrypoint needs to be [overridden](using_docker_images.md#overriding-the-entrypoint-of-an-image),
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otherwise the build script doesn't run.
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- A Docker `config.json` file needs to be created with the authentication
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information for the desired container registry.
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In the following example, kaniko is used to:
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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.
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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
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project's Container Registry while tagging it with the Git tag:
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```yaml
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build:
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stage: build
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image:
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name: gcr.io/kaniko-project/executor:debug
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entrypoint: [""]
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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)\"}}}" > /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:
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- if: $CI_COMMIT_TAG
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```
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### Building an image with kaniko behind a proxy
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If you use a custom GitLab Runner behind an http(s) proxy, kaniko needs to be set
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up accordingly. This means:
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- Adding the proxy to `/kaniko/.docker/config.json`
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- Passing the `http_proxy` environment variables as build arguments so the Dockerfile
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instructions can use the proxy when building the image.
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The previous example can be extended as follows:
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```yaml
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build:
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stage: build
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image:
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name: gcr.io/kaniko-project/executor:debug
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entrypoint: [""]
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script:
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- mkdir -p /kaniko/.docker
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- |-
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KANIKOPROXYBUILDARGS=""
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KANIKOCFG="{\"auths\":{\"$CI_REGISTRY\":{\"auth\":\"$(echo -n ${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD} | base64)\"}}}"
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if [ "x${http_proxy}" != "x" -o "x${https_proxy}" != "x" ]; then
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KANIKOCFG="${KANIKOCFG}, \"proxies\": { \"default\": { \"httpProxy\": \"${http_proxy}\", \"httpsProxy\": \"${https_proxy}\", \"noProxy\": \"${no_proxy}\"}}"
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KANIKOPROXYBUILDARGS="--build-arg http_proxy=${http_proxy} --build-arg https_proxy=${https_proxy} --build-arg no_proxy=${no_proxy}"
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fi
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KANIKOCFG="${KANIKOCFG} }"
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echo "${KANIKOCFG}" > /kaniko/.docker/config.json
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- /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile $KANIKOPROXYBUILDARGS --destination $CI_REGISTRY_IMAGE:$CI_COMMIT_TAG
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rules:
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- if: $CI_COMMIT_TAG
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```
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## Using a registry with a custom certificate
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When trying to push to a Docker registry that uses a certificate that is signed
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by a custom CA, you might get the following error:
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```shell
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$ /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --no-push
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INFO[0000] Downloading base image registry.gitlab.example.com/group/docker-image
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error building image: getting stage builder for stage 0: Get https://registry.gitlab.example.com/v2/: x509: certificate signed by unknown authority
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```
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This can be solved by adding your CA's certificate to the kaniko certificate
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store:
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```yaml
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before_script:
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- mkdir -p /kaniko/.docker
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- echo "{\"auths\":{\"$CI_REGISTRY\":{\"auth\":\"$(echo -n ${CI_REGISTRY_USER}:${CI_REGISTRY_PASSWORD} | base64)\"}}}" > /kaniko/.docker/config.json
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- |
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echo "-----BEGIN CERTIFICATE-----
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...
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-----END CERTIFICATE-----" >> /kaniko/ssl/certs/additional-ca-cert-bundle.crt
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```
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## Video walkthrough of a working example
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The [Least Privilege Container Builds with Kaniko on GitLab](https://www.youtube.com/watch?v=d96ybcELpFs)
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video is a walkthrough of the [Kaniko Docker Build](https://gitlab.com/guided-explorations/containers/kaniko-docker-build)
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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
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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`
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and `https_proxy` [environment variables](../../administration/packages/container_registry.md#running-the-docker-daemon-with-a-proxy)
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can fix the problem.
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