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TaskRuns

Overview

A TaskRun allows you to instantiate and execute a Task on-cluster. A Task specifies one or more Steps that execute container images and each container image performs a specific piece of build work. A TaskRun executes the Steps in the Task in the order they are specified until all Steps have executed successfully or a failure occurs.

Configuring a TaskRun

A TaskRun definition supports the following fields:

  • Required:
    • apiVersion - Specifies the API version, for example tekton.dev/v1beta1.
    • kind - Identifies this resource object as a TaskRun object.
    • metadata - Specifies the metadata that uniquely identifies the TaskRun, such as a name.
    • spec - Specifies the configuration for the TaskRun.
  • Optional:
    • serviceAccountName - Specifies a ServiceAccount object that provides custom credentials for executing the TaskRun.
    • params - Specifies the desired execution parameters for the Task.
    • resources (deprecated) - Specifies the desired PipelineResource values.
      • inputs - Specifies the input resources.
      • outputs - Specifies the output resources.
    • timeout - Specifies the timeout before the TaskRun fails.
    • podTemplate - Specifies a Pod template to use as the starting point for configuring the Pods for the Task.
    • workspaces - Specifies the physical volumes to use for the Workspaces declared by a Task.
    • debug- Specifies any breakpoints and debugging configuration for the Task execution.
    • stepOverrides - Specifies configuration to use to override the Task's Steps.
    • sidecarOverrides - Specifies configuration to use to override the Task's Sidecars.

Specifying the target Task

To specify the Task you want to execute in your TaskRun, use the taskRef field as shown below:

spec:
  taskRef:
    name: read-task

You can also embed the desired Task definition directly in the TaskRun using the taskSpec field:

spec:
  taskSpec:
    workspaces:
    - name: source
    steps:
      - name: build-and-push
        image: gcr.io/kaniko-project/executor:v0.17.1
        # specifying DOCKER_CONFIG is required to allow kaniko to detect docker credential
        workingDir: $(workspaces.source.path)
        env:
          - name: "DOCKER_CONFIG"
            value: "/tekton/home/.docker/"
        command:
          - /kaniko/executor
        args:
          - --destination=gcr.io/my-project/gohelloworld

Tekton Bundles

Note: This is only allowed if enable-tekton-oci-bundles is set to "true" or enable-api-fields is set to "alpha" in the feature-flags configmap, see install.md

You may also reference Tasks that are defined outside of your cluster using Tekton Bundles. A Tekton Bundle is an OCI artifact that contains Tekton resources like Tasks which can be referenced within a taskRef.

spec:
taskRef:
  name: echo-task
  bundle: docker.io/myrepo/mycatalog

Here, the bundle field is the full reference url to the artifact. The name is the metadata.name field of the Task.

You may also specify a tag as you would with a Docker image which will give you a repeatable reference to a Task.

spec:
taskRef:
  name: echo-task
  bundle: docker.io/myrepo/mycatalog:v1.0.1

You may also specify a fixed digest instead of a tag which ensures the referenced task is constant.

spec:
taskRef:
  name: echo-task
  bundle: docker.io/myrepo/mycatalog@sha256:abc123

A working example can be found here.

Any of the above options will fetch the image using the ImagePullSecrets attached to the ServiceAccount specified in the TaskRun. See the Service Account section for details on how to configure a ServiceAccount on a TaskRun. The TaskRun will then run that Task without registering it in the cluster allowing multiple versions of the same named Task to be run at once.

Tekton Bundles may be constructed with any toolsets that produces valid OCI image artifacts so long as the artifact adheres to the contract. Additionally, you may also use the tkn cli (coming soon).

Remote Tasks

(beta feature)

A taskRef field may specify a Task in a remote location such as git. Support for specific types of remote will depend on the Resolvers your cluster's operator has installed. For more information including a tutorial, please check resolution docs. The below example demonstrates referencing a Task in git:

spec:
  taskRef:
    resolver: git
    params:
    - name: url
      value: https://github.com/tektoncd/catalog.git
    - name: revision
      value: abc123
    - name: pathInRepo
      value: /task/golang-build/0.3/golang-build.yaml

Specifying Parameters

If a Task has parameters, you can use the params field to specify their values:

spec:
  params:
    - name: flags
      value: -someflag

Note: If a parameter does not have an implicit default value, you must explicitly set its value.

Propagated Parameters

When using an inlined taskSpec, parameters from the parent TaskRun will be available to the Task without needing to be explicitly defined.

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  generateName: hello-
spec:
  params:
    - name: message
      value: "hello world!"
  taskSpec:
    # There are no explicit params defined here.
    # They are derived from the TaskRun params above.
    steps:
    - name: default
      image: ubuntu
      script: |
        echo $(params.message)

On executing the task run, the parameters will be interpolated during resolution. The specifications are not mutated before storage and so it remains the same. The status is updated.

kind: TaskRun
metadata:
  name: hello-dlqm9
  ...
spec:
  params:
  - name: message
    value: hello world!
  serviceAccountName: default
  taskSpec:
    steps:
    - image: ubuntu
      name: default
      resources: {}
      script: |
        echo $(params.message)
status:
  conditions:
  - lastTransitionTime: "2022-05-20T15:24:41Z"
    message: All Steps have completed executing
    reason: Succeeded
    status: "True"
    type: Succeeded
  ... 
  steps:
  - container: step-default
    ...  
  taskSpec:
    steps:
    - image: ubuntu
      name: default
      resources: {}
      script: |
        echo "hello world!"

Propagated Object Parameters

(alpha only)

When using an inlined taskSpec, object parameters from the parent TaskRun will be available to the Task without needing to be explicitly defined.

Note: If an object parameter is being defined explicitly then you must define the spec of the object in Properties.

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  generateName: object-param-result-
spec:
  params:
  - name: gitrepo
    value:
      commit: sha123
      url: xyz.com
  taskSpec:
    steps:
    - name: echo-object-params
      image: bash
      args:
      - echo
      - --url=$(params.gitrepo.url)
      - --commit=$(params.gitrepo.commit)

On executing the task run, the object parameters will be interpolated during resolution. The specifications are not mutated before storage and so it remains the same. The status is updated.

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: object-param-result-vlnmb
  ...
spec:
  params:
  - name: gitrepo
    value:
      commit: sha123
      url: xyz.com
  serviceAccountName: default
  taskSpec:
    steps:
    - args:
      - echo
      - --url=$(params.gitrepo.url)
      - --commit=$(params.gitrepo.commit)
      image: bash
      name: echo-object-params
      resources: {}
status:
  completionTime: "2022-09-08T17:09:37Z"
  conditions:
  - lastTransitionTime: "2022-09-08T17:09:37Z"
    message: All Steps have completed executing
    reason: Succeeded
    status: "True"
    type: Succeeded
    ...
  steps:
  - container: step-echo-object-params
    ...
  taskSpec:
    steps:
    - args:
      - echo
      - --url=xyz.com
      - --commit=sha123
      image: bash
      name: echo-object-params
      resources: {}

Extra Parameters

(alpha only)

You can pass in extra Parameters if needed depending on your use cases. An example use case is when your CI system autogenerates TaskRuns and it has Parameters it wants to provide to all TaskRuns. Because you can pass in extra Parameters, you don't have to go through the complexity of checking each Task and providing only the required params.

Specifying Resources

⚠️ PipelineResources are deprecated.

Consider using replacement features instead. Read more in documentation and TEP-0074.

If a Task requires Resources (that is, inputs and outputs) you must specify them in your TaskRun definition. You can specify Resources by reference to existing PipelineResource objects or embed their definitions directly in the TaskRun.

Note: A TaskRun can use either a referenced or an embedded Resource but not both simultaneously.

Below is an example of specifying Resources by reference:

spec:
  resources:
    inputs:
      - name: workspace
        resourceRef:
          name: java-git-resource
    outputs:
      - name: image
        resourceRef:
          name: my-app-image

And here is an example of specifying Resources by embedding their definitions:

spec:
  resources:
    inputs:
      - name: workspace
        resourceSpec:
          type: git
          params:
            - name: url
              value: https://github.com/pivotal-nader-ziada/gohelloworld

Note: You can use the paths field to override the paths to a Resource.

Specifying Resource limits

Each Step in a Task can specify its resource requirements. See Defining Steps. Resource requirements defined in Steps and Sidecars may be overridden by a TaskRun's StepOverrides and SidecarOverrides.

Specifying Task-level ComputeResources

(alpha only)

Task-level compute resources can be configured in TaskRun.ComputeResources, or PipelineRun.TaskRunSpecs.ComputeResources.

e.g.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: task
spec:
  steps:
    - name: foo
---
apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: taskrun 
spec:
  taskRef:
    name: task
  computeResources:
    requests:
      cpu: 1 
    limits:
      cpu: 2

Further details and examples could be found in Compute Resources in Tekton.

Specifying a Pod template

You can specify a Pod template configuration that will serve as the configuration starting point for the Pod in which the container images specified in your Task will execute. This allows you to customize the Pod configuration specifically for that TaskRun.

In the following example, the Task specifies a volumeMount (my-cache) object, also provided by the TaskRun, using a PersistentVolumeClaim volume. A specific scheduler is also configured in the SchedulerName field. The Pod executes with regular (non-root) user permissions.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: mytask
  namespace: default
spec:
  steps:
    - name: writesomething
      image: ubuntu
      command: ["bash", "-c"]
      args: ["echo 'foo' > /my-cache/bar"]
      volumeMounts:
        - name: my-cache
          mountPath: /my-cache
---
apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: mytaskrun
  namespace: default
spec:
  taskRef:
    name: mytask
  podTemplate:
    schedulerName: volcano
    securityContext:
      runAsNonRoot: true
      runAsUser: 1001
    volumes:
      - name: my-cache
        persistentVolumeClaim:
          claimName: my-volume-claim

Specifying Workspaces

If a Task specifies one or more Workspaces, you must map those Workspaces to the corresponding physical volumes in your TaskRun definition. For example, you can map a PersistentVolumeClaim volume to a Workspace as follows:

workspaces:
  - name: myworkspace # must match workspace name in the Task
    persistentVolumeClaim:
      claimName: mypvc # this PVC must already exist
    subPath: my-subdir

For more information, see the following topics:

Propagated Workspaces

beta)

When using an embedded spec, workspaces from the parent TaskRun will be propagated to any inlined specs without needing to be explicitly defined. This allows authors to simplify specs by automatically propagating top-level workspaces down to other inlined resources. Workspace substutions will only be made for commands, args and script fields of steps, stepTemplates, and sidecars.

apiVersion: tekton.dev/v1beta1 
kind: TaskRun                  
metadata:
  generateName: propagating-workspaces-
spec:
  taskSpec:                    
    steps:                     
      - name: simple-step      
        image: ubuntu          
        command:               
          - echo               
        args:                  
          - $(workspaces.tr-workspace.path)
  workspaces:                  
  - emptyDir: {}               
    name: tr-workspace

Upon execution, the workspaces will be interpolated during resolution through to the taskspec.

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: propagating-workspaces-ndxnc
  ...
spec:
  ...
status:
  ...
  taskSpec:
    steps:
      ...
    workspaces:
    - name: tr-workspace
Propagating Workspaces to Referenced Tasks

Workspaces can only be propagated to embedded task specs, not referenced Tasks.

apiVersion: tekton.dev/v1beta1 
kind: Task                     
metadata:
  name: workspace-propagation
spec:
  steps:
    - name: simple-step        
      image: ubuntu            
      command:                 
        - echo                 
      args:                    
        - $(workspaces.tr-workspace.path)
---
apiVersion: tekton.dev/v1beta1 
kind: TaskRun
metadata:
  generateName: propagating-workspaces-
spec:
  taskRef:                     
    name: workspace-propagation
  workspaces:                  
  - emptyDir: {}               
    name: tr-workspace

Upon execution, the above taskrun will fail because the task is referenced and workspace is not propagated. It mist be explicitly defined in the spec of the defined Task.

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  ...
spec:
  taskRef:
    kind: Task
    name: workspace-propagation
  workspaces:
  - emptyDir: {}
    name: tr-workspace
status:
  conditions:
  - lastTransitionTime: "2022-09-13T15:12:35Z"
    message: workspace binding "tr-workspace" does not match any declared workspace
    reason: TaskRunValidationFailed
    status: "False"
    type: Succeeded
  ...

Specifying Sidecars

A Sidecar is a container that runs alongside the containers specified in the Steps of a task to provide auxiliary support to the execution of those Steps. For example, a Sidecar can run a logging daemon, a service that updates files on a shared volume, or a network proxy.

Tekton supports the injection of Sidecars into a Pod belonging to a TaskRun with the condition that each Sidecar running inside the Pod are terminated as soon as all Steps in the Task complete execution. This might result in the Pod including each affected Sidecar with a retry count of 1 and a different container image than expected.

We are aware of the following issues affecting Tekton's implementation of Sidecars:

  • The configured nop image must not provide the command that the Sidecar is expected to run, otherwise it will not exit, resulting in the Sidecar running forever and the Task eventually timing out. For more information, see the associated issue.

  • The kubectl get pods command returns the status of the Pod as "Completed" if a Sidecar exits successfully and as "Error" if a Sidecar exits with an error, disregarding the exit codes of the container images that actually executed the Steps inside the Pod. Only the above command is affected. The Pod's description correctly denotes a "Failed" status and the container statuses correctly denote their exit codes and reasons.

Overriding Task Steps and Sidecars

(alpha only)

A TaskRun can specify StepOverrides or SidecarOverrides to override Step or Sidecar configuration specified in a Task. Only named Steps and Sidecars may be overridden.

For example, given the following Task definition:

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: image-build-task
spec:
  steps:
    - name: build
      image: gcr.io/kaniko-project/executor:latest
  sidecars:
    - name: logging
      image: my-logging-image

An example TaskRun definition could look like:

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: image-build-taskrun
spec:
  taskRef:
    name: image-build-task
  stepOverrides:
    - name: build
      resources:
        requests:
          memory: 1Gi
  sidecarOverrides:
    - name: logging
      resources:
        requests:
          cpu: 100m
        limits:
          cpu: 500m

StepOverrides and SidecarOverrides must include the name field and may include resources. No other fields can be overridden. If the overridden Task uses a StepTemplate, configuration on Step will take precedence over configuration in StepTemplate, and configuration in StepOverride will take precedence over both.

When merging resource requirements, different resource types are considered independently. For example, if a Step configures both CPU and memory, and a StepOverride configures only memory, the CPU values from the Step will be preserved. Requests and limits are also considered independently. For example, if a Step configures a memory request and limit, and a StepOverride configures only a memory request, the memory limit from the Step will be preserved.

Specifying LimitRange values

In order to only consume the bare minimum amount of resources needed to execute one Step at a time from the invoked Task, Tekton will requests the compute values for CPU, memory, and ephemeral storage for each Step based on the LimitRange object(s), if present. Any Request or Limit specified by the user (on Task for example) will be left unchanged.

For more information, see the LimitRange support in Pipeline.

Specifying Retries

You can use the retries field to set how many times you want to retry on a failed TaskRun. All TaskRun failures are retriable except for Cancellation.

For a retriable TaskRun, when an error occurs:

  • The error status is archived in status.RetriesStatus
  • The Succeeded condition in status is updated:
Type: Succeeded
Status: Unknown
Reason: ToBeRetried
  • status.StartTime and status.PodName are unset to trigger another retry attempt.

Configuring the failure timeout

You can use the timeout field to set the TaskRun's desired timeout value for each retry attempt. If you do not specify this value, the global default timeout value applies (the same, to each retry attempt). If you set the timeout to 0, the TaskRun will have no timeout and will run until it completes successfully or fails from an error.

The global default timeout is set to 60 minutes when you first install Tekton. You can set a different global default timeout value using the default-timeout-minutes field in config/config-defaults.yaml. If you set the global timeout to 0, all TaskRuns that do not have a timeout set will have no timeout and will run until it completes successfully or fails from an error.

The timeout value is a duration conforming to Go's ParseDuration format. For example, valid values are 1h30m, 1h, 1m, 60s, and 0.

If a TaskRun runs longer than its timeout value, the pod associated with the TaskRun will be deleted. This means that the logs of the TaskRun are not preserved. The deletion of the TaskRun pod is necessary in order to stop TaskRun step containers from running.

Specifying ServiceAccount credentials

You can execute the Task in your TaskRun with a specific set of credentials by specifying a ServiceAccount object name in the serviceAccountName field in your TaskRun definition. If you do not explicitly specify this, the TaskRun executes with the credentials specified in the configmap-defaults ConfigMap. If this default is not specified, TaskRuns will execute with the default service account set for the target namespace.

For more information, see ServiceAccount.

Monitoring execution status

As your TaskRun executes, its status field accumulates information on the execution of each Step as well as the TaskRun as a whole. This information includes start and stop times, exit codes, the fully-qualified name of the container image, and the corresponding digest.

Note: If any Pods have been OOMKilled by Kubernetes, the TaskRun is marked as failed even if its exit code is 0.

The following example shows the status field of a TaskRun that has executed successfully:

completionTime: "2019-08-12T18:22:57Z"
conditions:
  - lastTransitionTime: "2019-08-12T18:22:57Z"
    message: All Steps have completed executing
    reason: Succeeded
    status: "True"
    type: Succeeded
podName: status-taskrun-pod
startTime: "2019-08-12T18:22:51Z"
steps:
  - container: step-hello
    imageID: docker-pullable://busybox@sha256:895ab622e92e18d6b461d671081757af7dbaa3b00e3e28e12505af7817f73649
    name: hello
    terminated:
      containerID: docker://d5a54f5bbb8e7a6fd3bc7761b78410403244cf4c9c5822087fb0209bf59e3621
      exitCode: 0
      finishedAt: "2019-08-12T18:22:56Z"
      reason: Completed
      startedAt: "2019-08-12T18:22:54Z"

The following tables shows how to read the overall status of a TaskRun:

status reason message completionTime is set Description
Unknown Started n/a No The TaskRun has just been picked up by the controller.
Unknown Pending n/a No The TaskRun is waiting on a Pod in status Pending.
Unknown Running n/a No The TaskRun has been validated and started to perform its work.
Unknown TaskRunCancelled n/a No The user requested the TaskRun to be cancelled. Cancellation has not been done yet.
True Succeeded n/a Yes The TaskRun completed successfully.
False Failed n/a Yes The TaskRun failed because one of the steps failed.
False [Error message] n/a No The TaskRun encountered a non-permanent error, and it's still running. It may ultimately succeed.
False [Error message] n/a Yes The TaskRun failed with a permanent error (usually validation).
False TaskRunCancelled n/a Yes The TaskRun was cancelled successfully.
False TaskRunCancelled TaskRun cancelled as the PipelineRun it belongs to has timed out. Yes The TaskRun was cancelled because the PipelineRun timed out.
False TaskRunTimeout n/a Yes The TaskRun timed out.
False TaskRunImagePullFailed n/a Yes The TaskRun failed due to one of its steps not being able to pull the image.

When a TaskRun changes status, events are triggered accordingly.

The name of the Pod owned by a TaskRun is univocally associated to the owning resource. If a TaskRun resource is deleted and created with the same name, the child Pod will be created with the same name as before. The base format of the name is <taskrun-name>-pod. The name may vary according to the logic of kmeta.ChildName. In case of retries of a TaskRun triggered by the PipelineRun controller, the base format of the name is <taskrun-name>-pod-retry<N> starting from the first retry.

Some examples:

TaskRun Name Pod Name
task-run task-run-pod
task-run-0123456789-0123456789-0123456789-0123456789-0123456789-0123456789 task-run-0123456789-01234560d38957287bb0283c59440df14069f59-pod

Monitoring Steps

If multiple Steps are defined in the Task invoked by the TaskRun, you can monitor their execution status in the status.steps field using the following command, where <name> is the name of the target TaskRun:

kubectl get taskrun <name> -o yaml

The exact Task Spec used to instantiate the TaskRun is also included in the Status for full auditability.

Steps

The corresponding statuses appear in the status.steps list in the order in which the Steps have been specified in the Task definition.

Monitoring Results

If one or more results fields have been specified in the invoked Task, the TaskRun's execution status will include a Task Results section, in which the Results appear verbatim, including original line returns and whitespace. For example:

Status:
  # […]
  Steps:
  # […]
  Task Results:
    Name:   current-date-human-readable
    Value:  Thu Jan 23 16:29:06 UTC 2020

    Name:   current-date-unix-timestamp
    Value:  1579796946

Cancelling a TaskRun

To cancel a TaskRun that's currently executing, update its status to mark it as cancelled.

When you cancel a TaskRun, the running pod associated with that TaskRun is deleted. This means that the logs of the TaskRun are not preserved. The deletion of the TaskRun pod is necessary in order to stop TaskRun step containers from running.

Example of cancelling a TaskRun:

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: go-example-git
spec:
  # […]
  status: "TaskRunCancelled"

Debugging a TaskRun

Breakpoint on Failure

TaskRuns can be halted on failure for troubleshooting by providing the following spec patch as seen below.

spec:
  debug:
    breakpoint: ["onFailure"]

Upon failure of a step, the TaskRun Pod execution is halted. If this TaskRun Pod continues to run without any lifecycle change done by the user (running the debug-continue or debug-fail-continue script) the TaskRun would be subject to TaskRunTimeout. During this time, the user/client can get remote shell access to the step container with a command such as the following.

kubectl exec -it print-date-d7tj5-pod -c step-print-date-human-readable

Debug Environment

After the user/client has access to the container environment, they can scour for any missing parts because of which their step might have failed.

To control the lifecycle of the step to mark it as a success or a failure or close the breakpoint, there are scripts provided in the /tekton/debug/scripts directory in the container. The following are the scripts and the tasks they perform :-

debug-continue: Mark the step as a success and exit the breakpoint.

debug-fail-continue: Mark the step as a failure and exit the breakpoint.

More information on the inner workings of debug can be found in the Debug documentation

Code examples

To better understand TaskRuns, study the following code examples:

Example TaskRun with a referenced Task

In this example, a TaskRun named read-repo-run invokes and executes an existing Task named read-task. This Task reads the repository from the "input" workspace.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: read-task
spec:
  workspaces:
  - name: input
  steps:
    - name: readme
      image: ubuntu
      script: cat $(workspaces.input.path)/README.md
---
apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: read-repo-run
spec:
  taskRef:
    name: read-task
  workspaces:
  - name: input
    persistentVolumeClaim:
      claimName: mypvc
    subPath: my-subdir

Example TaskRun with an embedded Task

In this example, a TaskRun named build-push-task-run-2 directly executes a Task from its definition embedded in the TaskRun's taskSpec field:

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: build-push-task-run-2
spec:
  workspaces:
  - name: source
    persistentVolumeClaim:
      claimName: my-pvc
  taskSpec:
    workspaces:
    - name: source
    steps:
      - name: build-and-push
        image: gcr.io/kaniko-project/executor:v0.17.1
        workingDir: $(workspaces.source.path)
        # specifying DOCKER_CONFIG is required to allow kaniko to detect docker credential
        env:
          - name: "DOCKER_CONFIG"
            value: "/tekton/home/.docker/"
        command:
          - /kaniko/executor
        args:
          - --destination=gcr.io/my-project/gohelloworld

You can also embed resource definitions in your TaskRun. In the example below, a git resource definition provides input for the TaskRun named read-repo:

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: read-repo
spec:
  taskRef:
    name: read-task
  resources:
    inputs:
      - name: workspace
        resourceSpec:
          type: git
          params:
            - name: url
              value: https://github.com/pivotal-nader-ziada/gohelloworld

Example of Using custom ServiceAccount credentials

The example below illustrates how to specify a ServiceAccount to access a private git repository:

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: test-task-with-serviceaccount-git-ssh
spec:
  serviceAccountName: test-task-robot-git-ssh
  workspaces:
  - name: source
    persistentVolumeClaim:
      claimName: repo-pvc
  - name: ssh-creds
    secret:
      secretName: test-git-ssh
  params:
    - name: url
      value: https://github.com/tektoncd/pipeline.git
  taskRef:
    name: git-clone

In the above code snippet, serviceAccountName: test-build-robot-git-ssh references the following ServiceAccount:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-task-robot-git-ssh
secrets:
  - name: test-git-ssh

And secretName: test-git-ssh references the following Secret:

apiVersion: v1
kind: Secret
metadata:
  name: test-git-ssh
  annotations:
    tekton.dev/git-0: github.com
type: kubernetes.io/ssh-auth
data:
  # Generated by:
  # cat id_rsa | base64 -w 0
  ssh-privatekey: LS0tLS1CRUdJTiBSU0EgUFJJVk.....[example]
  # Generated by:
  # ssh-keyscan github.com | base64 -w 0
  known_hosts: Z2l0aHViLmNvbSBzc2g.....[example]

Example of Running Step Containers as a Non Root User

All steps that do not require to be run as a root user should make use of TaskRun features to designate the container for a step runs as a user without root permissions. As a best practice, running containers as non root should be built into the container image to avoid any possibility of the container being run as root. However, as a further measure of enforcing this practice, TaskRun pod templates can be used to specify how containers should be run within a TaskRun pod.

An example of using a TaskRun pod template is shown below to specify that containers running via this TaskRun's pod should run as non root and run as user 1001 if the container itself does not specify what user to run as:

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  generateName: show-non-root-steps-run-
spec:
  taskRef:
    name: show-non-root-steps
  podTemplate:
    securityContext:
      runAsNonRoot: true
      runAsUser: 1001

If a Task step specifies that it is to run as a different user than what is specified in the pod template, the step's securityContext will be applied instead of what is specified at the pod level. An example of this is available as a TaskRun example.

More information about Pod and Container Security Contexts can be found via the Kubernetes website.

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