• Workflow
• Connecting to the Kubernetes API
• Kubernetes executor interaction diagram
• The available config.toml settings
  • CPU requests and limits
  • Memory requests and limits
  • Storage requests and limits
  • Other config.toml settings
  • Configuring executor Service Account
  • Overwriting Kubernetes Namespace
  • Overwriting Kubernetes Default Service Account
  • Setting Bearer Token to be Used When Making Kubernetes API calls
  • Overwriting pod labels
  • Overwriting pod annotations
  • Overwriting Container Resources
• Define settings in the configuration TOML
• Resources check during prepare step
• Using the cache with the Kubernetes executor
• Using volumes
  • Host Path volumes
  • PVC volumes
  • ConfigMap volumes
  • Secret volumes
  • Empty Dir volumes
  • CSI volumes
  • Mounting volumes on service containers
• Custom builds directory mount
• Using Security Context
  • Container security context
• Using services
• Using pull policies
• Using node selectors
  • Example for linux/arm64
  • Example for windows/amd64
• Adding extra host aliases
• Using Affinity
  • Node Affinity
  • Pod affinity and anti-affinity
• Container lifecycle hooks
  • KubernetesLifecycleExecAction
  • KubernetesLifecycleHTTPGet
  • KubernetesLifecycleHTTPGetHeader
  • KubernetesLifecycleTcpSocket
• Pod’s DNS Config
  • KubernetesDNSConfigOption
• Capabilities configuration
  • Default list of dropped capabilities
  • Example configuration
• Using Runtime Class
• Using Docker in your builds
  • Exposing /var/run/docker.sock
  • Using docker:dind
  • Resource separation
  • Using kaniko
  • Restricting Docker images and services
  • Restrict Docker pull policies
• Job execution
  • Container entrypoint
• Pod cleanup
• Troubleshooting
  • Job failed (system failure): timed out waiting for pod to start
  • context deadline exceeded
  • Connection refused when attempting to communicate with the Kubernetes API
  • Error cleaning up pod and Job failed (system failure): prepare environment: waiting for pod running
  • request did not complete within requested timeout
  • fatal: unable to access 'https://gitlab-ci-token:token@example.com/repo/proj.git/': Could not resolve host: example.com
  • docker: Cannot connect to the Docker daemon at tcp://docker:2375. Is the docker daemon running?
  • curl: (35) OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443
  • MountVolume.SetUp failed for volume "kube-api-access-xxxxx" : chown is not supported by windows
  • Build pods are assigned the worker node’s IAM role instead of Runner IAM role
  • Preparation failed: failed to pull image ‘image-name:latest’: pull_policy ([Always]) defined in GitLab pipeline config is not one of the allowed_pull_policies ([])
• Restrict access to job variables

The Kubernetes executor for GitLab Runner

GitLab Runner can use Kubernetes to run builds on a Kubernetes cluster. This is possible with the use of the Kubernetes executor.

The Kubernetes executor, when used with GitLab CI, connects to the Kubernetes API in the cluster creating a Pod for each GitLab CI Job. This Pod is made up of, at the very least, a build container, a helper container, and an additional container for each service defined in the .gitlab-ci.yml or config.toml files. The names for these containers are as follows:

• The build container is build
• The helper container is helper
• The services containers are svc-X where X is [0-9]+

Note that when services and containers are running in the same Kubernetes pod, they are all sharing the same localhost address. The following restrictions are then applicable:

• Since GitLab Runner 12.8 and Kubernetes 1.7, the services are accessible via their DNS names. If you are using an older version you will have to use localhost.
• You cannot use several services using the same port (e.g., you cannot have two mysql services at the same time).

Workflow

The Kubernetes executor divides the build into multiple steps:

1. Prepare: Create the Pod against the Kubernetes Cluster. This creates the containers required for the build and services to run.
2. Pre-build: Clone, restore cache and download artifacts from previous stages. This is run on a special container as part of the Pod.
3. Build: User build.
4. Post-build: Create cache, upload artifacts to GitLab. This also uses the special container as part of the Pod.

Connecting to the Kubernetes API

The following options are provided, which allow you to connect to the Kubernetes API:

• host: Optional Kubernetes apiserver host URL (auto-discovery attempted if not specified)
• cert_file: Optional Kubernetes apiserver user auth certificate
• key_file: Optional Kubernetes apiserver user auth private key
• ca_file: Optional Kubernetes apiserver ca certificate

The user account provided must have permission to create, list and attach to Pods in the specified namespace in order to function.

If you are running GitLab Runner within the Kubernetes cluster you can omit all of the above fields to have GitLab Runner auto-discover the Kubernetes API. This is the recommended approach.

If you are running it externally to the Cluster then you will need to set each of these settings and make sure that GitLab Runner has access to the Kubernetes API on the cluster.

Kubernetes executor interaction diagram

The diagram below depicts the interaction with a GitLab Runner hosted on a Kubernetes cluster and the Kubernetes API. The Kubernetes API is the mechanism that is used by GitLab Runner on Kubernetes to create pods on the cluster. The interaction depicted in this diagram is valid on any Kubernetes cluster, whether that’s a turnkey solution hosted on the major public cloud providers or a self-managed Kubernetes installation.

The available config.toml settings

The following settings help to define the behavior of GitLab Runner within Kubernetes.

CPU requests and limits

Memory requests and limits

Storage requests and limits

Other config.toml settings

Configuring executor Service Account

You can set the KUBERNETES_SERVICE_ACCOUNT environment variable or use --kubernetes-service-account flag.

Overwriting Kubernetes Namespace

The Kubernetes namespace can be overwritten per CI/CD job in the .gitlab-ci.yml file, by using the variable KUBERNETES_NAMESPACE_OVERWRITE.

You can use this approach to designate a namespace for CI purposes, and deploy a custom set of Pods to it. The Pods spawned by the runner take place on the overwritten namespace, for simple and straight forward access between containers during the CI stages.

variables:
  KUBERNETES_NAMESPACE_OVERWRITE: ci-${CI_COMMIT_REF_SLUG}

Furthermore, to ensure only designated namespaces will be used during CI runs, set the configuration namespace_overwrite_allowed with an appropriate regular expression. When left empty the overwrite behavior is disabled.

When you overwrite the Kubernetes namespace, make sure that:

• In the values.yml file for GitLab Runner Helm charts, this value is set: rbac.clusterWideAccess: true.

• The runner has these permissions in the core API group:

  • For exec strategy:

    Resource	Permissions
    pods/exec	create, patch, delete
    pods	get, list, watch, create, patch, delete
    services	get, list, watch, create, patch, delete
    secrets	get, list, watch, create, update, patch, delete
    serviceAccounts	get (1)

  • For attach strategy:

    Resource	Permissions
    pods/attach	create, patch, delete
    pods/exec	create, patch, delete
    pods	get, watch, create, delete
    services	get, watch, create, delete
    configmaps	get, create, update, delete
    secrets	get, create, update, delete
    serviceAccounts	get (1)

(1) The serviceAccount permission is needed only:

• For GitLab 15.0 and 15.1.
• For GitLab 15.0.1, 15.1.1, and 15.2 when resource_availability_check_max_attempts is set to a value higher than 0.

This can be achieved by setting rbac.create: true or by specifying a service account rbac.serviceAccountName: <service_account_name> with the above permissions in the values.yml file.

Overwriting Kubernetes Default Service Account

Additionally, the Kubernetes service account can be overwritten per CI/CD job in the .gitlab-ci.yml file, by using the variable KUBERNETES_SERVICE_ACCOUNT_OVERWRITE.

This approach allows you to specify a service account that is attached to the namespace, which is useful when dealing with complex RBAC configurations.

variables:
  KUBERNETES_SERVICE_ACCOUNT_OVERWRITE: ci-service-account

To ensure only designated service accounts will be used during CI runs, set the configuration service_account_overwrite_allowed or set the environment variable KUBERNETES_SERVICE_ACCOUNT_OVERWRITE_ALLOWED with an appropriate regular expression. When left empty, the overwrite behavior is disabled.

Setting Bearer Token to be Used When Making Kubernetes API calls

In conjunction with setting the namespace and service account as mentioned above, you may set the bearer token used when making API calls to create the build pods. This will allow project owners to use project secret variables to specify a bearer token. When specifying the bearer token, you must set the Host configuration setting.

variables:
  KUBERNETES_BEARER_TOKEN: thebearertokenfromanothernamespace

Overwriting pod labels

You can overwrite Kubernetes pod labels per CI/CD job.

First, ensure you specify pod_labels_overwrite_allowed in your .config.yaml file.

Then, in your .gitlab-ci.yml file, use the KUBERNETES_POD_LABELS_* variables with values of key=value. The pod labels are overwritten to the key=value.

You can apply multiple values. For example:

variables:
  KUBERNETES_POD_LABELS_1: "Key1=Val1"
  KUBERNETES_POD_LABELS_2: "Key2=Val2"
  KUBERNETES_POD_LABELS_3: "Key3=Val3"

Overwriting pod annotations

Additionally, Kubernetes pod annotations can be overwritten per CI/CD job in the .gitlab-ci.yml file, by using KUBERNETES_POD_ANNOTATIONS_* for variables and key=value for the value. The pod annotations will be overwritten to the key=value. Multiple annotations can be applied. For example:

variables:
  KUBERNETES_POD_ANNOTATIONS_1: "Key1=Val1"
  KUBERNETES_POD_ANNOTATIONS_2: "Key2=Val2"
  KUBERNETES_POD_ANNOTATIONS_3: "Key3=Val3"

Overwriting Container Resources

Additionally, Kubernetes CPU and memory allocations for requests and limits for the build, helper and service containers can be overwritten per CI/CD job, in the .gitlab-ci.yml file, with the following variables:

 variables:
   KUBERNETES_CPU_REQUEST: "3"
   KUBERNETES_CPU_LIMIT: "5"
   KUBERNETES_MEMORY_REQUEST: "2Gi"
   KUBERNETES_MEMORY_LIMIT: "4Gi"
   KUBERNETES_EPHEMERAL_STORAGE_REQUEST: "512Mi"
   KUBERNETES_EPHEMERAL_STORAGE_LIMIT: "1Gi"

   KUBERNETES_HELPER_CPU_REQUEST: "3"
   KUBERNETES_HELPER_CPU_LIMIT: "5"
   KUBERNETES_HELPER_MEMORY_REQUEST: "2Gi"
   KUBERNETES_HELPER_MEMORY_LIMIT: "4Gi"
   KUBERNETES_HELPER_EPHEMERAL_STORAGE_REQUEST: "512Mi"
   KUBERNETES_HELPER_EPHEMERAL_STORAGE_LIMIT: "1Gi"

   KUBERNETES_SERVICE_CPU_REQUEST: "3"
   KUBERNETES_SERVICE_CPU_LIMIT: "5"
   KUBERNETES_SERVICE_MEMORY_REQUEST: "2Gi"
   KUBERNETES_SERVICE_MEMORY_LIMIT: "4Gi"
   KUBERNETES_SERVICE_EPHEMERAL_STORAGE_REQUEST: "512Mi"
   KUBERNETES_SERVICE_EPHEMERAL_STORAGE_LIMIT: "1Gi"

The values for these variables are restricted to the max overwrite setting for that resource. If the max overwrite has not been set for a resource, the variable is ignored.

Define settings in the configuration TOML

Each of the settings can be defined in the config.toml file.

Here is an example config.toml:

concurrent = 4

[[runners]]
  name = "myRunner"
  url = "https://gitlab.com/ci"
  token = "......"
  executor = "kubernetes"
  [runners.kubernetes]
    host = "https://45.67.34.123:4892"
    cert_file = "/etc/ssl/kubernetes/api.crt"
    key_file = "/etc/ssl/kubernetes/api.key"
    ca_file = "/etc/ssl/kubernetes/ca.crt"
    namespace = "gitlab"
    namespace_overwrite_allowed = "ci-.*"
    bearer_token_overwrite_allowed = true
    privileged = true
    cpu_limit = "1"
    memory_limit = "1Gi"
    service_cpu_limit = "1"
    service_memory_limit = "1Gi"
    helper_cpu_limit = "500m"
    helper_memory_limit = "100Mi"
    poll_interval = 5
    poll_timeout = 3600
    dns_policy = "cluster-first"
    priority_class_name = "priority-1"
    [runners.kubernetes.node_selector]
      gitlab = "true"
    [runners.kubernetes.node_tolerations]
      "node-role.kubernetes.io/master" = "NoSchedule"
      "custom.toleration=value" = "NoSchedule"
      "empty.value=" = "PreferNoSchedule"
      "onlyKey" = ""

Resources check during prepare step

Prerequisites:

• image_pull_secrets or service_account is set.
• resource_availability_check_max_attempts is set to a number greater than zero.
• Kubernetes serviceAccount used with the get and list permissions.

GitLab Runner checks if the new service accounts or secrets are available with a 5-second interval between each try. The number of times to check is equal to the value of resource_availability_check_max_attempts.

• In GitLab 15.0 and 15.1, you cannot disable this feature and it defaults to 5 when a negative value is set.
• In GitLab 15.0.1, 15.1.1, 15.2 and later, this feature is disabled by default and can be enabled by setting the resource_availability_check_max_attempts to any value other than 0

Using the cache with the Kubernetes executor

When the cache is used with the Kubernetes executor, a specific volume called /cache is mounted on the pod. The cache volume can be configured in the config.toml file by using the cache_dir setting.

During the job’s execution, if the cached data is needed, the runner checks to see if cached data is available (if a compressed file is available on the cache volume).

• If available, the compressed file is extracted into the build folder and can then be used in the job.
• If not available, the cached data is downloaded from the configured storage and saved into the cache dir as a compressed file. The compressed file is then extracted into the build folder.

Using volumes

As described earlier, volumes can be mounted in the build container. At this time hostPath, PVC, configMap, secret, and CSI volume types are supported. Users can configure any number of volumes for each of mentioned types.

Here is an example configuration:

concurrent = 4

[[runners]]
  # usual configuration
  executor = "kubernetes"
  [runners.kubernetes]
    [[runners.kubernetes.volumes.host_path]]
      name = "hostpath-1"
      mount_path = "/path/to/mount/point"
      read_only = true
      host_path = "/path/on/host"
    [[runners.kubernetes.volumes.host_path]]
      name = "hostpath-2"
      mount_path = "/path/to/mount/point_2"
      read_only = true
    [[runners.kubernetes.volumes.pvc]]
      name = "pvc-1"
      mount_path = "/path/to/mount/point1"
    [[runners.kubernetes.volumes.config_map]]
      name = "config-map-1"
      mount_path = "/path/to/directory"
      [runners.kubernetes.volumes.config_map.items]
        "key_1" = "relative/path/to/key_1_file"
        "key_2" = "key_2"
    [[runners.kubernetes.volumes.secret]]
      name = "secrets"
      mount_path = "/path/to/directory1"
      read_only = true
      [runners.kubernetes.volumes.secret.items]
        "secret_1" = "relative/path/to/secret_1_file"
    [[runners.kubernetes.volumes.empty_dir]]
      name = "empty-dir"
      mount_path = "/path/to/empty_dir"
      medium = "Memory"
    [[runners.kubernetes.volumes.csi]]
      name = "csi-volume"
      mount_path = "/path/to/csi/volume"
      driver = "my-csi-driver"
      [runners.kubernetes.volumes.csi.volume_attributes]
        size = "2Gi"

Host Path volumes

HostPath volume configuration instructs Kubernetes to mount a specified host path inside of the container. The volume can be configured with following options:

PVC volumes

PVC volume configuration instructs Kubernetes to use a PersistentVolumeClaim that is defined in Kubernetes cluster and mount it inside of the container. The volume can be configured with following options:

ConfigMap volumes

ConfigMap volume configuration instructs Kubernetes to use a configMap that is defined in Kubernetes cluster and mount it inside of the container.

When using configMap volume, each key from selected configMap will be changed into a file stored inside of the selected mount path. By default all keys are present, configMap’s key is used as file’s name and value is stored as file’s content. The default behavior can be changed with items option.

items option is defining a mapping between key that should be used and path (relative to volume’s mount path) where configMap’s value should be saved. When using items option only selected keys will be added to the volumes and all other will be skipped.

Notice: If a non-existing key will be used then job will fail on Pod creation stage.

Secret volumes

Secret volume configuration instructs Kubernetes to use a secret that is defined in Kubernetes cluster and mount it inside of the container.

When using secret volume each key from selected secret will be changed into a file stored inside of the selected mount path. By default all keys are present, secret’s key is used as file’s name and value is stored as file’s content. The default behavior can be changed with items option.

items option is defining a mapping between key that should be used and path (relative to volume’s mount path) where secret’s value should be saved. When using items option only selected keys will be added to the volumes and all other will be skipped.

Notice: If a non-existing key will be used then job will fail on Pod creation stage.

Empty Dir volumes

emptyDir volume configuration instructs Kubernetes to mount an empty directory inside of the container.

CSI volumes

CSI volume configuration instructs Kubernetes to use a custom CSI driver to mount an arbitrary storage system inside of the container.

Mounting volumes on service containers

Volumes defined for the build container are also automatically mounted for all services containers. This can be, for example, leveraged to mount database storage in RAM to speed up tests, as an alternative to services_tmpfs which is only available to the Docker executor.

Here is an example configuration:

[[runners]]
  # usual configuration
  executor = "kubernetes"
  [runners.kubernetes]
    [[runners.kubernetes.volumes.empty_dir]]
      name = "mysql-tmpfs"
      mount_path = "/var/lib/mysql"
      medium = "Memory"

Custom builds directory mount

To store the builds directory for the job, define custom volume mounts to the configured builds_dir (/builds by default). To use PVC volumes, be aware that depending on the access mode, you might be limited to running jobs on 1 node.

Here is an example configuration:

concurrent = 4

[[runners]]
  # usual configuration
  executor = "kubernetes"
  builds_dir = "/builds"
  [runners.kubernetes]
    [[runners.kubernetes.volumes.empty_dir]]
      name = "repo"
      mount_path = "/builds"
      medium = "Memory"

Using Security Context

Pod security context configuration instructs executor to set a pod security policy on the build pod.

Assigning a security context to pods provides security to your Kubernetes cluster. For this to work you’ll need to provide a helper image that conforms to the policy you set here.

Read more about the helper image. Example of building your own helper image:

ARG tag
FROM registry.gitlab.com/gitlab-org/ci-cd/gitlab-runner-ubi-images/gitlab-runner-helper-ocp:${tag}
USER root
RUN groupadd -g 59417 nonroot && \
    useradd -u 59417 nonroot -g nonroot
WORKDIR /home/nonroot
USER 59417:59417

This example creates a user and group called nonroot and sets the image to run as that user.

Example of setting pod security context in your config.toml:

concurrent = %(concurrent)s
check_interval = 30
  [[runners]]
    name = "myRunner"
    url = "gitlab.example.com"
    executor = "kubernetes"
    [runners.kubernetes]
      helper_image = "gitlab-registry.example.com/helper:latest"
      [runners.kubernetes.pod_security_context]
        run_as_non_root = true
        run_as_user = 59417
        run_as_group = 59417
        fs_group = 59417

Container security context

Use the container security context configuration to configure the executor to set a container security policy on the build, helper, or service pods.

The example below sets a pod security context, then overrides run_as_user and run_as_group for both the build and helper containers. In the example, all service containers would inherit run_as_user and run_as_group from the pod security context.

Example of setting pod security context in your config.toml:

concurrent = 4
check_interval = 30
  [[runners]]
    name = "myRunner"
    url = "gitlab.example.com"
    executor = "kubernetes"
    [runners.kubernetes]
      helper_image = "gitlab-registry.example.com/helper:latest"
      [runners.kubernetes.pod_security_context]
        run_as_non_root = true
        run_as_user = 59417
        run_as_group = 59417
        fs_group = 59417
      [runners.kubernetes.init_permissions_container_security_context]
        run_as_user = 1000
        run_as_group = 1000
      [runners.kubernetes.build_container_security_context]
        run_as_user = 65534
        run_as_group = 65534
        [runners.kubernetes.build_container_security_context.capabilities]
          add = ["NET_ADMIN"]
      [runners.kubernetes.helper_container_security_context]
        run_as_user = 1000
        run_as_group = 1000
      [runners.kubernetes.service_container_security_context]
        run_as_user = 1000
        run_as_group = 1000

Using services

Define a list of services.

concurrent = 1
check_interval = 30
  [[runners]]
    name = "myRunner"
    url = "gitlab.example.com"
    executor = "kubernetes"
    [runners.kubernetes]
      helper_image = "gitlab-registy.example.com/helper:latest"
      [[runners.kubernetes.services]]
        name = "postgres:12-alpine"
        alias = "db1"
      [[runners.kubernetes.services]]
        name = "registry.example.com/svc1"
        alias = "svc1"
        entrypoint = ["entrypoint.sh"]
        command = ["executable","param1","param2"]

Using pull policies

Use the pull_policy parameter to specify a single or multiple pull policies.

For a single pull policy:

[runners.kubernetes]
  pull_policy = "never"

For multiple pull policies:

[runners.kubernetes]
  # use multiple pull policies
  pull_policy = ["always", "if-not-present"]

To retry a failed pull:

[runners.kubernetes]
  pull_policy = ["always", "always"]

The policy applies to the build image, helper image, and any services. It controls how an image is fetched and updated.

To determine when to use which policy, see the documentation on Kubernetes pull policies.

The GitLab naming convention is slightly different than the Kubernetes one.

When multiple policies are defined, each policy is attempted until the image is obtained successfully. For example, when you use [ always, if-not-present ], you can use the policy if-not-present if always fails due to a temporary registry problem.

Beware of the security considerations when using if-not-present.

Using node selectors

The node_selector option can be used to specify which node in a Kubernetes cluster you want builds to be executed on. It is a table of key=value pairs in the format of string=string (string:string in the case of environment variables).

Runner additionally uses the information provided to determine the OS and architecture for the build. This ensures that the correct helper image is used. By default, the OS and architecture is assumed to be linux/amd64.

By using certain labels, builds can be scheduled on nodes with different operating systems and architectures:

Example for linux/arm64

  [[runners]]
    name = "myRunner"
    url = "gitlab.example.com"
    executor = "kubernetes"

    [runners.kubernetes.node_selector]
      "kubernetes.io/arch" = "arm64"
      "kubernetes.io/os" = "linux"

Example for windows/amd64

Kubernetes for Windows has certain limitations, so if process-isolation is used, you must additionally provide the specific windows build version with the node.kubernetes.io/windows-build label.

  [[runners]]
    name = "myRunner"
    url = "gitlab.example.com"
    executor = "kubernetes"

    # The FF_USE_POWERSHELL_PATH_RESOLVER feature flag has to be enabled for PowerShell
    # to resolve paths for Windows correctly when Runner is operating in a Linux environment
    # but targeting Windows nodes.
    environment = ["FF_USE_POWERSHELL_PATH_RESOLVER=1"]

    [runners.kubernetes.node_selector]
      "kubernetes.io/arch" = "amd64"
      "kubernetes.io/os" = "windows"
      "node.kubernetes.io/windows-build" = "10.0.19041"

Adding extra host aliases

This feature is available in Kubernetes 1.7+.

Host aliases configuration instructs Kubernetes to add entries to /etc/hosts file inside of the container. The host aliases can be configured with the following options:

Here is an example configuration:

concurrent = 4

[[runners]]
  # usual configuration
  executor = "kubernetes"
  [runners.kubernetes]
    [[runners.kubernetes.host_aliases]]
      ip = "127.0.0.1"
      hostnames = ["web1", "web2"]
    [[runners.kubernetes.host_aliases]]
      ip = "192.168.1.1"
      hostnames = ["web14", "web15"]

Using Affinity

Node Affinity

Define a list of node affinities to be added to a pod specification at build time.

concurrent = 1
[[runners]]
  name = "myRunner"
  url = "gitlab.example.com"
  executor = "kubernetes"
  [runners.kubernetes]
    [runners.kubernetes.affinity]
      [runners.kubernetes.affinity.node_affinity]
        [[runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution]]
          weight = 100
          [runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution.preference]
            [[runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution.preference.match_expressions]]
              key = "cpu_speed"
              operator = "In"
              values = ["fast"]
            [[runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution.preference.match_expressions]]
              key = "mem_speed"
              operator = "In"
              values = ["fast"]
        [[runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution]]
          weight = 50
          [runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution.preference]
            [[runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution.preference.match_expressions]]
              key = "core_count"
              operator = "In"
              values = ["high", "32"]
            [[runners.kubernetes.affinity.node_affinity.preferred_during_scheduling_ignored_during_execution.preference.match_fields]]
              key = "cpu_type"
              operator = "In"
              values = ["arm64"]
      [runners.kubernetes.affinity.node_affinity.required_during_scheduling_ignored_during_execution]
        [[runners.kubernetes.affinity.node_affinity.required_during_scheduling_ignored_during_execution.node_selector_terms]]
          [[runners.kubernetes.affinity.node_affinity.required_during_scheduling_ignored_during_execution.node_selector_terms.match_expressions]]
            key = "kubernetes.io/e2e-az-name"
            operator = "In"
            values = [
              "e2e-az1",
              "e2e-az2"
            ]

Pod affinity and anti-affinity

Use these affinities to constrain which nodes your pod is eligible to be scheduled on based on the labels on other pods.

concurrent = 1
[[runners]]
  name = "myRunner"
  url = "gitlab.example.com"
  executor = "kubernetes"
  [runners.kubernetes]
    [runners.kubernetes.affinity]
      [runners.kubernetes.affinity.pod_affinity]
        [[runners.kubernetes.affinity.pod_affinity.required_during_scheduling_ignored_during_execution]]
          topology_key = "failure-domain.beta.kubernetes.io/zone"
          namespaces = ["namespace_1", "namespace_2"]
          [runners.kubernetes.affinity.pod_affinity.required_during_scheduling_ignored_during_execution.label_selector]
            [[runners.kubernetes.affinity.pod_affinity.required_during_scheduling_ignored_during_execution.label_selector.match_expressions]]
              key = "security"
              operator = "In"
              values = ["S1"]
        [[runners.kubernetes.affinity.pod_affinity.preferred_during_scheduling_ignored_during_execution]]
        weight = 100
        [runners.kubernetes.affinity.pod_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term]
          topology_key = "failure-domain.beta.kubernetes.io/zone"
          [runners.kubernetes.affinity.pod_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term.label_selector]
            [[runners.kubernetes.affinity.pod_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term.label_selector.match_expressions]]
              key = "security_2"
              operator = "In"
              values = ["S2"]
      [runners.kubernetes.affinity.pod_anti_affinity]
        [[runners.kubernetes.affinity.pod_anti_affinity.required_during_scheduling_ignored_during_execution]]
          topology_key = "failure-domain.beta.kubernetes.io/zone"
          namespaces = ["namespace_1", "namespace_2"]
          [runners.kubernetes.affinity.pod_anti_affinity.required_during_scheduling_ignored_during_execution.label_selector]
            [[runners.kubernetes.affinity.pod_anti_affinity.required_during_scheduling_ignored_during_execution.label_selector.match_expressions]]
              key = "security"
              operator = "In"
              values = ["S1"]
          [runners.kubernetes.affinity.pod_anti_affinity.required_during_scheduling_ignored_during_execution.namespace_selector]
            [[runners.kubernetes.affinity.pod_anti_affinity.required_during_scheduling_ignored_during_execution.namespace_selector.match_expressions]]
              key = "security"
              operator = "In"
              values = ["S1"]
        [[runners.kubernetes.affinity.pod_anti_affinity.preferred_during_scheduling_ignored_during_execution]]
        weight = 100
        [runners.kubernetes.affinity.pod_anti_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term]
          topology_key = "failure-domain.beta.kubernetes.io/zone"
          [runners.kubernetes.affinity.pod_anti_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term.label_selector]
            [[runners.kubernetes.affinity.pod_anti_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term.label_selector.match_expressions]]
              key = "security_2"
              operator = "In"
              values = ["S2"]
          [runners.kubernetes.affinity.pod_anti_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term.namespace_selector]
            [[runners.kubernetes.affinity.pod_anti_affinity.preferred_during_scheduling_ignored_during_execution.pod_affinity_term.namespace_selector.match_expressions]]
              key = "security_2"
              operator = "In"
              values = ["S2"]

Container lifecycle hooks

Use container lifecycle hooks to run code configured for a handler when the corresponding lifecycle hook is executed. You can configure two types of hooks: PreStop and PostStart. Each of them allows only one type of handler to be set.

Here is an example configuration:

[[runners]]
  name = "kubernetes"
  url = "https://gitlab.example.com/"
  executor = "kubernetes"
  token = "yrnZW46BrtBFqM7xDzE7dddd"
  [runners.kubernetes]
    image = "alpine:3.11"
    privileged = true
    namespace = "default"
    [runners.kubernetes.container_lifecycle.post_start.exec]
      command = ["touch", "/builds/postStart.txt"]
    [runners.kubernetes.container_lifecycle.pre_stop.http_get]
      port = 8080
      host = "localhost"
      path = "/test"
      [[runners.kubernetes.container_lifecycle.pre_stop.http_get.http_headers]]
        name = "header_name_1"
        value = "header_value_1"
      [[runners.kubernetes.container_lifecycle.pre_stop.http_get.http_headers]]
        name = "header_name_2"
        value = "header_value_2"

Each lifecycle hook is configured through the following settings:

KubernetesLifecycleExecAction

KubernetesLifecycleHTTPGet

KubernetesLifecycleHTTPGetHeader

KubernetesLifecycleTcpSocket

Pod’s DNS Config

Pod’s DNS Config gives users more control on the DNS settings of the created build Pods.

concurrent = 1
check_interval = 30
[[runners]]
  name = "myRunner"
  url = "https://gitlab.example.com"
  token = "__REDACTED__"
  executor = "kubernetes"
  [runners.kubernetes]
    image = "alpine:latest"
    [runners.kubernetes.dns_config]
      nameservers = [
        "1.2.3.4",
      ]
      searches = [
        "ns1.svc.cluster-domain.example",
        "my.dns.search.suffix",
      ]

      [[runners.kubernetes.dns_config.options]]
        name = "ndots"
        value = "2"

      [[runners.kubernetes.dns_config.options]]
        name = "edns0"

KubernetesDNSConfigOption

Capabilities configuration

Kubernetes allows to configure different Linux capabilities that should be added or dropped from a container.

GitLab Runner supports configuration of capabilities with the cap_add and cap_drop settings in the [runners.kubernetes] section of the configuration file. By default, GitLab Runner provides a list of capabilities that should be dropped.

Because the default list of dropped capabilities can intersect with user-defined capabilities, the following rules are applied to determine the final list:

1. User-defined cap_drop has priority over user-defined cap_add. If you define the same capability in both settings, only the one from cap_drop is passed to the container.

2. User-defined cap_add has priority over the default list of dropped capabilities. If you want to add the capability that is dropped by default, explicitly add it to cap_add.

The final list of capabilities is added to all containers in the job’s pod.

A few notes:

• Remove the CAP_ prefix from capability identifiers passed to the container configuration. For example, if you want to add or drop the CAP_SYS_TIME capability, in the configuration file, set a SYS_TIME string for cap_add or cap_drop.

• The owner of the Kubernetes cluster can define a PodSecurityPolicy, where specific capabilities are allowed, restricted, or added by default. These rules take precedence over any user-defined configuration.

  Container runtimes can also define a default list of capabilities that you can add, like those seen in Docker or containerd.

Default list of dropped capabilities

GitLab Runner tries to drop these capabilities by default. If any of them are required for the job to be executed properly, you should explicitly add the capability with the cap_add setting:

• NET_RAW

Example configuration

concurrent = 1
check_interval = 30
[[runners]]
  name = "myRunner"
  url = "gitlab.example.com"
  executor = "kubernetes"
  [runners.kubernetes]
    # ...
    cap_add = ["SYS_TIME", "IPC_LOCK"]
    cap_drop = ["SYS_ADMIN"]
    # ...

Using Runtime Class

Use runtime_class_name to set the RuntimeClass for each job container.

If you specify runtime_class_name and it’s not configured in your cluster or the feature is not supported, job pods fail to create.

concurrent = 1
check_interval = 30
  [[runners]]
    name = "myRunner"
    url = "gitlab.example.com"
    executor = "kubernetes"
    [runners.kubernetes]
      runtime_class_name = "myclass"

Using Docker in your builds

There are a couple of caveats when using Docker in your builds while running on a Kubernetes cluster. Most of these issues are already discussed in the Using Docker Build section of the GitLab CI documentation but it is worthwhile to revisit them here as you might run into some slightly different things when running this on your cluster.

Exposing /var/run/docker.sock

Exposing your host’s /var/run/docker.sock into your build container, using the runners.kubernetes.volumes.host_path option, brings the same risks with it as always. That node’s containers are accessible from the build container and depending if you are running builds in the same cluster as your production containers it might not be wise to do that.

Using docker:dind

Running the docker:dind also known as the docker-in-docker image is also possible but sadly needs the containers to be run in privileged mode. If you’re willing to take that risk other problems will arise that might not seem as straight forward at first glance. Because the Docker daemon is started as a service usually in your .gitlab-ci.yml it will be run as a separate container in your Pod. Basically containers in Pods only share volumes assigned to them and an IP address by which they can reach each other using localhost. /var/run/docker.sock is not shared by the docker:dind container and the docker binary tries to use it by default.

To overwrite this and make the client use TCP to contact the Docker daemon, in the other container, be sure to include the environment variables of the build container:

• DOCKER_HOST=tcp://<hostname>:2375 for no TLS connection.
• DOCKER_HOST=tcp://<hostname>:2376 for TLS connection.

If you are using GitLab Runner 12.7 or earlier and Kubernetes 1.6 or earlier, the value of hostname must be set to localhost. Otherwise it should be set to docker.

Make sure to configure those properly. As of Docker 19.03, TLS is enabled by default but it requires mapping certificates to your client. You can enable non-TLS connection for DIND or mount certificates as described in Use Docker In Docker Workflow with Docker executor

Resource separation

In both the docker:dind and /var/run/docker.sock cases the Docker daemon has access to the underlying kernel of the host machine. This means that any limits that had been set in the Pod will not work when building Docker images. The Docker daemon will report the full capacity of the node regardless of the limits imposed on the Docker build containers spawned by Kubernetes.

One way to help minimize the exposure of the host’s kernel to any build container when running in privileged mode or by exposing /var/run/docker.sock is to use the node_selector option to set one or more labels that have to match a node before any containers are deployed to it. For example build containers may only run on nodes that are labeled with role=ci while running all other production services on other nodes. Further separation of build containers can be achieved using node taints. This prevents other pods from scheduling on the same nodes as the build pods without extra configuration for the other pods.

Using kaniko

Another approach for building Docker images inside a Kubernetes cluster is using kaniko. kaniko:

• Allows you to build images without privileged access.
• Works without the Docker daemon.

For more information, see Building images with kaniko and GitLab CI/CD.

Restricting Docker images and services

Added for the Kubernetes executor in GitLab Runner 14.2.

You can restrict the Docker images that are used to run your jobs. To do this, you specify wildcard patterns. For example, to allow images from your private Docker registry only:

[[runners]]
  (...)
  executor = "kubernetes"
  [runners.kubernetes]
    (...)
    allowed_images = ["my.registry.tld:5000/*:*"]
    allowed_services = ["my.registry.tld:5000/*:*"]

Or, to restrict to a specific list of images from this registry:

[[runners]]
  (...)
  executor = "kubernetes"
  [runners.kubernetes]
    (...)
    allowed_images = ["my.registry.tld:5000/ruby:*", "my.registry.tld:5000/node:*"]
    allowed_services = ["postgres:9.4", "postgres:latest"]

Restrict Docker pull policies

In the .gitlab-ci.yml file, you can specify a pull policy. This policy determines how a CI/CD job should fetch images.

To restrict which pull policies can be used in the .gitlab-ci.yml file, you can use allowed_pull_policies.

For example, to allow only the always and if-not-present pull policies:

[[runners]]
  (...)
  executor = "kubernetes"
  [runners.kubernetes]
    (...)
    allowed_pull_policies = ["always", "if-not-present"]

• If you don’t specify allowed_pull_policies, the default is the value in the pull_policy keyword.
• If you don’t specify pull_policy, the cluster’s image default pull policy is used.
• The existing pull_policy keyword must not include a pull policy that is not specified in allowed_pull_policies. If it does, the job returns an error.

Job execution

GitLab Runner uses kube attach instead of kube exec by default. This should avoid problems like when a job is marked successful midway in environments with an unstable network.

If you experience problems after updating to GitLab Runner 14.0, toggle the feature flag FF_USE_LEGACY_KUBERNETES_EXECUTION_STRATEGY to true and submit an issue.

Follow issue #27976 for progress on legacy execution strategy removal.

Container entrypoint

• From GitLab 14.5 to 15.0, GitLab Runner honors the entrypoint defined in a Docker image when used with the Kubernetes executor with kube attach.
• From GitLab 15.1, the entrypoint defined in a Docker image is honored with the Kubernetes executor when FF_KUBERNETES_HONOR_ENTRYPOINT is set.

Pod cleanup

Sometimes old runner pods are not cleared. This can happen when Runner Manager is incorrectly shut down.

To handle this situation, you can use the GitLab Runner Pod Cleanup application to schedule cleanup of old pods. For more information, see:

• The GitLab Runner Pod Cleanup project README.
• GitLab Runner Pod Cleanup documentation.

Troubleshooting

The following errors are commonly encountered when using the Kubernetes executor.

Job failed (system failure): timed out waiting for pod to start

If the cluster cannot schedule the build pod before the timeout defined by poll_timeout, the build pod returns an error. The Kubernetes Scheduler should be able to delete it.

To fix this issue, increase the poll_timeout value in your config.toml file.

context deadline exceeded

The context deadline exceeded errors in job logs usually indicate that the Kubernetes API client hit a timeout for a given cluster API request.

Check the metrics of the kube-apiserver cluster component for any signs of:

• Increased response latencies.
• Error rates for common create or delete operations over pods, secrets, ConfigMaps, and other core (v1) resources.

Logs for timeout-driven errors from the kube-apiserver operations may appear as:

Job failed (system failure): prepare environment: context deadline exceeded
Job failed (system failure): prepare environment: setting up build pod: context deadline exceeded

In some cases, the kube-apiserver error response might provide additional details of its sub-components failing (such as the Kubernetes cluster’s etcdserver):

Job failed (system failure): prepare environment: etcdserver: request timed out
Job failed (system failure): prepare environment: etcdserver: leader changed
Job failed (system failure): prepare environment: Internal error occurred: resource quota evaluates timeout

These kube-apiserver service failures can occur during the creation of the build pod and also during cleanup attempts after completion:

Error cleaning up secrets: etcdserver: request timed out
Error cleaning up secrets: etcdserver: leader changed

Error cleaning up pod: etcdserver: request timed out, possibly due to previous leader failure
Error cleaning up pod: etcdserver: request timed out
Error cleaning up pod: context deadline exceeded

Connection refused when attempting to communicate with the Kubernetes API

When GitLab Runner makes a request to the Kubernetes API and it fails, it is likely because kube-apiserver is overloaded and can’t accept or process API requests.

Error cleaning up pod and Job failed (system failure): prepare environment: waiting for pod running

The following errors occur when Kubernetes fails to schedule the job pod in a timely manner. GitLab Runner waits for the pod to be ready, but it fails and then tries to clean up the pod, which can also fail.

Error: Error cleaning up pod: Delete "https://xx.xx.xx.x:443/api/v1/namespaces/gitlab-runner/runner-0001": dial tcp xx.xx.xx.x:443 connect: connection refused

Error: Job failed (system failure): prepare environment: waiting for pod running: Get "https://xx.xx.xx.x:443/api/v1/namespaces/gitlab-runner/runner-0001": dial tcp xx.xx.xx.x:443 connect: connection refused

To troubleshoot, check the Kubernetes primary node and all nodes that run a kube-apiserver instance. Ensure they have all of the resources needed to manage the target number of pods that you hope to scale up to on the cluster.

To change the time GitLab Runner waits for a pod to reach its Ready status, use the poll_timeout setting.

To better understand how pods are scheduled or why they might not get scheduled on time, read about the Kubernetes Scheduler.

request did not complete within requested timeout

The message request did not complete within requested timeout observed during build pod creation indicates that a configured admission control webhook on the Kubernetes cluster is timing out.

Admission control webhooks are a cluster-level administrative control intercept for all API requests they’re scoped for, and can cause failures if they do not execute in time.

Admission control webhooks support filters that can finely control which API requests and namespace sources it intercepts. If the Kubernetes API calls from GitLab Runner do not need to pass through an admission control webhook then you may alter the webhook’s selector/filter configuration to ignore the GitLab Runner namespace, or apply exclusion labels/annotations over the GitLab Runner pod by configuring podAnnotations or podLabels in the GitLab Runner Helm Chart values.yaml.

For example, to avoid DataDog Admission Controller webhook from intercepting API requests made by the GitLab Runner manager pod, the following can be added:

podLabels:
  admission.datadoghq.com/enabled: false

To list a Kubernetes cluster’s admission control webhooks, run:

kubectl get validatingwebhookconfiguration -o yaml
kubectl get mutatingwebhookconfiguration -o yaml

The following forms of logs can be observed when an admission control webhook times out:

Job failed (system failure): prepare environment: Timeout: request did not complete within requested timeout
Job failed (system failure): prepare environment: setting up credentials: Timeout: request did not complete within requested timeout

A failure from an admission control webhook may instead appear as:

Job failed (system failure): prepare environment: setting up credentials: Internal error occurred: failed calling webhook "example.webhook.service"

fatal: unable to access 'https://gitlab-ci-token:token@example.com/repo/proj.git/': Could not resolve host: example.com

If using the alpine flavor of the helper image, there can be DNS issues related to Alpine’s musl’s DNS resolver.

Using the helper_image_flavor = "ubuntu" option should resolve this.

docker: Cannot connect to the Docker daemon at tcp://docker:2375. Is the docker daemon running?

This error can occur when using Docker-in-Docker if attempts are made to access the DIND service before it has had time to fully start up. For a more detailed explanation, see this issue.

curl: (35) OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443

This error can happen when using Docker-in-Docker if the DIND Maximum Transmission Unit (MTU) is larger than the Kubernetes overlay network. DIND uses a default MTU of 1500, which is too large to route across the default overlay network. The DIND MTU can be changed within the service definition:

services:
  - name: docker:dind
    command: ["--mtu=1450"]

MountVolume.SetUp failed for volume "kube-api-access-xxxxx" : chown is not supported by windows

When you run your CI/CD job, you might receive an error like the following:

MountVolume.SetUp failed for volume "kube-api-access-xxxxx" : chown c:\var\lib\kubelet\pods\xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\volumes\kubernetes.io~projected\kube-api-access-xxxxx\..2022_07_07_20_52_19.102630072\token: not supported by windows

This issue occurs when you use node selectors to run builds on nodes with different operating systems and architectures.

To fix the issue, configure nodeSelector so that the Runner Manager pod is always scheduled on a Linux node. For example, your values.yaml file should contain the following:

nodeSelector:
  kubernetes.io/os: linux

Build pods are assigned the worker node’s IAM role instead of Runner IAM role

This issue happens when the worker node IAM role does not have the permission to assume the correct role. To fix this, add the sts:AssumeRole permission to the trust relationship of the worker node’s IAM role:

{
    "Effect": "Allow",
    "Principal": {
        "AWS": "arn:aws:iam::<AWS_ACCOUNT_NUMBER>:role/<IAM_ROLE_NAME>"
    },
    "Action": "sts:AssumeRole"
}

Preparation failed: failed to pull image ‘image-name:latest’: pull_policy ([Always]) defined in GitLab pipeline config is not one of the allowed_pull_policies ([])

This issue happens if you specified a pull_policy in your .gitlab-ci.yml but there is no policy configured in the Runner’s config file. To fix this, add allowed_pull_policies to your config according to Restrict Docker pull policies.

Restrict access to job variables

When using Kubernetes executor, users with access to the Kubernetes cluster can read variables used in the job. By default, job variables are stored in:

• ConfigMap - There is an ongoing MR to change this
• Pod’s environment section

To restrict access to job variable data, you should use role-based access control (RBAC) so that only GitLab administrators have access to the namespace used by the GitLab Runner.

If you need other users to access the GitLab Runner namespace, set the following verbs to restrict the type of access users have in the GitLab Runner namespace:

• For pods and configmaps:
  • get
  • watch
  • list
• For pods/exec and pods/attach, use create.

Example RBAC definition for authorized users:

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: gitlab-runner-authorized-users
rules:
- apiGroups: [""]
  resources: ["configmaps", "pods"]
  verbs: ["get", "watch", "list"]
- apiGroups: [""]
  resources: ["pods/exec", "pods/attach"]
  verbs: ["create"]