Clone a git repository with Tekton

How to clone source code from git with Tekton Pipelines.

This guide shows you how to:

  1. Create a Task to clone source code from a git repository.
  2. Create a second Task to read the source code from a shared Workspace.

If you are already familiar with Tekton and just want to see the example, you can skip to the full code samples.

Prerequisites

  1. To follow this How-to you must have a Kubernetes cluster up and running and kubectl properly configured to issue commands to your cluster.

  2. Install Tekton Pipelines:

    kubectl apply --filename \
https://storage.googleapis.com/tekton-releases/pipeline/latest/release.yaml

    See the Pipelines installation documentation for other installation options.

  3. Install the Tekton CLI, tkn, on your machine.

If this is your first time using Tekton Pipelines, we recommend that you complete the Getting Started tutorials before proceeding with this guide.

Pull source code from git

In this section you are going to create a Pipeline containing a Task to pull code from a git repository.

Create the Pipeline

One practical aspect of Tekton Tasks and Pipelines is that they are reusable. There’s a community hub with a curated list of Pipelines and Tasks that you can include in your own CI/CD workflow. You are going to reuse one of those Tasks in this guide.

  1. Create a new Pipeline, pipeline.yaml:

    apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: clone-read

    The name clone-read is going to be used by the PipelineRun to refer to this Pipeline. This name can also be used with the CLI, to check logs, delete the pipeline, etc.

  2. Add the repository URL to the list of Pipeline parameters:

    spec:
  description: | 
    This pipeline clones a git repo, then echoes the README file to the stdout.
  params:
  - name: repo-url
    type: string
    description: The git repo URL to clone from.

    The params section contains a list of parameters to be used by the Tasks in this Pipeline. For now there is only one, repo-url.

  3. Add a Workspace, a shared volume to store the code this task is going to download:

    workspaces:
- name: shared-data
  description: | 
    This workspace contains the cloned repo files, so they can be read by the
    next task.

  4. Create the Task that is going to use the parameter and the Workplace that you just defined:

    tasks:
- name: fetch-source
  taskRef:
    name: git-clone
  workspaces:
  - name: output
    workspace: shared-data
  params:
  - name: url
    value: $(params.repo-url)

    This Task, fetch-source, refers to another Task, git-clone; to be installed from the community hub. A Task has its own params and workspaces passed down from the ones defined at Pipeline level. In this case, the names for the parameter url and the Workspace output are the the ones expected by the git clone Task spec. See the git clone documentation for more parameters and options.

Check the full code samples to see how all the pieces fit together in the file.

Create the PipelineRun

  1. Now that you have a Pipeline, to instantiate it and set the actual values, create a PipelineRun, pipelinerun.yaml:

    apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  name: clone-read-run
spec:
  pipelineRef:
    name: clone-read

    This PipelineRun, clone-read-run, instantiates clone-read, as specified by the pipelineRef target in the spec section.

  2. Instantiate the Workspace:

    workspaces:
- name: shared-data
  volumeClaimTemplate:
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 1Gi

    This creates a Persistent Volume Claim to store the cloned files. The name shared-data matches the name used in the Pipeline.

  3. Set the value of the repository URL parameter:

    params:
- name: repo-url
  value: https://github.com/tektoncd/website

    For this example you are going to clone the Tekton documentation website source code.

Check the full code samples to see full PipelineRun code.

Git authentication

For the sake of this example, we are using a public repository, which requires no authentication. If you want to clone a private repository, you must create a Kubernetes Secret with your credentials, then pass that secret to your Task as a Workspace.

Before you proceed, you have to set up SSH authentication with your git provider. The process may be slightly different in each case:

The following steps show you how to authenticate using an SSH key. For other forms of authentication check the git-clone Task documentation and the Git authentication section in the Pipelines documentation.

  1. Create a Kubernetes Secret with your credentials, for example:

    apiVersion: v1
kind: Secret
metadata:
  name: git-credentials
data:
  id_rsa: AS0tLS...
  known_hosts: AG033S...
  config: GS0FFL...

    The values for the fields under data are the corresponding base64-encoded files in the .ssh directory. For example, for id_rsa copy-paste the output of:

    cat ~/.ssh/id_rsa | base64 -w0

  2. Update pipeline.yaml, add a new Workspace to both the Pipeline and the Task:

    workspaces:
- name: shared-data
  description: | 
    This workspace contains the cloned repo files, so they can be read by the
    next task.
- name: git-credentials
  description: My ssh credentials
tasks:
- name: fetch-source
  taskRef:
    name: git-clone
  workspaces:
  - name: output
    workspace: shared-data
  - name: ssh-directory
    workspace: git-credentials

    The Workspace git-credentials is defined at Pipeline level and then passed down to the Task as ssh-directory, which is the name the Task expects.

  3. Update pipelinerun.yaml to use the Secret as a Workspace and change the git URL from https to SSH:

    workspaces:
- name: shared-data
  volumeClaimTemplate:
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 1Gi
- name: git-credentials
  secret:
    secretName: git-credentials
params:
- name: repo-url
  value: git@github.com:tektoncd/website.git

    The new Workspace name, git-credentials, matches the Workspace added to the Pipeline.

Use the source code in a second task

To learn how to share data between Tasks using a Workspace, you are going to create a second Task that displays the README file from the cloned git repository. You can find more useful examples in the How-to section and the examples folder in the Pipelines git repository.

  1. Add a new entry to the tasks section of pipelines.yaml:

    - name: show-readme
  runAfter: ["fetch-source"]
  taskRef:
    name: show-readme
  workspaces:
  - name: source
    workspace: shared-data

    This is referencing the Task show-readme. Unlike git clone, this Task is not from the Tekton community hub, you have to create it yourself.

  2. Create a file called show-readme.yaml and add the following:

    apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: show-readme
  description: Read and display README file.
spec:
  workspaces:
  - name: source
  steps:
  - name: read
    image: alpine:latest
    script: | 
      #!/usr/bin/env sh
      cat $(workspaces.source.path)/README.md

    This Task uses a Workspace that was already set. You don’t have to update pipelinerun.yaml.

Run the Pipeline

Install a Task from Tekton Hub

To use the git clone Task in your pipeline, you have to install it on your cluster first. You can do this with the tkn command:

tkn hub install task git-clone

Or using kubectl:

kubectl apply -f \
https://raw.githubusercontent.com/tektoncd/catalog/main/task/git-clone/0.6/git-clone.yaml

Alternatively, you can bundle a Task or a Pipeline and let your Pipeline fetch it directly from a registry.

Apply the files

Now you are ready to test the code.

  1. Apply the show-readme Task:

    kubectl apply -f show-readme.yaml

  2. Apply the Pipeline:

    kubectl apply -f pipeline.yaml

  3. Apply the PipelineRun:

    kubectl apply -f pipelinerun.yaml

  4. Monitor the Pipeline execution:

    tkn pipelinerun logs clone-read-run -f

    You may have to wait a few seconds. The output confirms that the respository was cloned succesfully and displays the README file at the end:

    [fetch-source : clone] + '[' false '=' true ]
[fetch-source : clone] + '[' false '=' true ]
[fetch-source : clone] + '[' false '=' true ]
[fetch-source : clone] + CHECKOUT_DIR=/workspace/output/
[fetch-source : clone] + '[' true '=' true ]
[fetch-source : clone] + cleandir
[fetch-source : clone] + '[' -d /workspace/output/ ]
[fetch-source : clone] + rm -rf '/workspace/output//*'
[fetch-source : clone] + rm -rf '/workspace/output//.[!.]*'
[fetch-source : clone] + rm -rf '/workspace/output//..?*'
[fetch-source : clone] + test -z 
[fetch-source : clone] + test -z 
[fetch-source : clone] + test -z 
[fetch-source : clone] + /ko-app/git-init '-url=https://github.com/tektoncd/website' '-revision=' '-refspec=' '-path=/workspace/output/' '-sslVerify=true' '-submodules=true' '-depth=1' '-sparseCheckoutDirectories='
[fetch-source : clone] {"level":"info","ts":1652300245.5099113,"caller":"git/git.go:170","msg":"Successfully cloned https://github.com/tektoncd/website @ 4930334b17edeaa737e2e6d0c7f7139b0afb1896 (grafted, HEAD) in path /workspace/output/"}
[fetch-source : clone] {"level":"info","ts":1652300245.5349698,"caller":"git/git.go:208","msg":"Successfully initialized and updated submodules in path /workspace/output/"}
[fetch-source : clone] + cd /workspace/output/
[fetch-source : clone] + git rev-parse HEAD
[fetch-source : clone] + RESULT_SHA=4930334b17edeaa737e2e6d0c7f7139b0afb1896
[fetch-source : clone] + EXIT_CODE=0
[fetch-source : clone] + '[' 0 '!=' 0 ]
[fetch-source : clone] + printf '%s' 4930334b17edeaa737e2e6d0c7f7139b0afb1896
[fetch-source : clone] + printf '%s' https://github.com/tektoncd/website

[show-readme : read] # TektonCD Website
[show-readme : read] 
[show-readme : read] This repo contains the code behind [the Tekton org's](https://github.com/tektoncd)
[show-readme : read] website at [tekton.dev](https://tekton.dev).
[show-readme : read] 
[show-readme : read] For more information on the Tekton Project, see
[show-readme : read] [the community repo](https://github.com/tektoncd/community).
[show-readme : read] 
[show-readme : read] For more information on contributing to the website see:
[show-readme : read] 
[show-readme : read] * [CONTRIBUTING.md](CONTRIBUTING.md)
[show-readme : read] * [DEVELOPMENT.md](DEVELOPMENT.md)

Full code samples

The Pipeline:

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: clone-read
spec:
  description: | 
    This pipeline clones a git repo, then echoes the README file to the stout.
  params:
  - name: repo-url
    type: string
    description: The git repo URL to clone from.
  workspaces:
  - name: shared-data
    description: | 
      This workspace contains the cloned repo files, so they can be read by the
      next task.
  - name: git-credentials
    description: My ssh credentials
  tasks:
  - name: fetch-source
    taskRef:
      name: git-clone
    workspaces:
    - name: output
      workspace: shared-data
    - name: ssh-directory
      workspace: git-credentials
    params:
    - name: url
      value: $(params.repo-url)
  - name: show-readme
    runAfter: ["fetch-source"]
    taskRef:
      name: show-readme
    workspaces:
    - name: source
      workspace: shared-data

The PipelineRun:

apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  name: clone-read-run
spec:
  pipelineRef:
    name: clone-read
  workspaces:
  - name: shared-data
    volumeClaimTemplate:
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
  - name: git-credentials
    secret:
      secretName: git-credentials
  params:
  - name: repo-url
    value: git@github.com:tektoncd/website.git

The show-readme Task:

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: show-readme
  description: Read and display README file.
spec:
  workspaces:
  - name: source
  steps:
  - name: read
    image: alpine:latest
    script: | 
      #!/usr/bin/env sh
      cat $(workspaces.source.path)/README.md

The Kubernetes Secret. These values are not real, check the section about git authentication to figure out how to encode your credentials.

apiVersion: v1
kind: Secret
metadata:
  name: git-credentials
data:
  id_rsa: AS0tLS...
  known_hosts: AG033S...

Further reading


Last modified July 19, 2022: Fix code typos (5f0df0d)