Configure VM startup routines

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When you use Anthos clusters on bare metal version 1.13.0 and later, you can specify startup routines to customize the initialization of your VM on startup. You can configure your VM to create SSH keys, add users and passwords, install packages, write files, configure network settings, and more.

These startup tasks are configured with either the cloud-init API or with startup scripts API (not both). These startup directives are specified in the VirtualMachine YAML manifest file and execute automatically each time your VM starts.

Prerequisites

In order to configure a VM with startup directives, you must meet the following prerequisites:

  • Enable Anthos VM Runtime.

  • Use a verified Linux guest OS and set osType to Linux in the VM manifest. Windows guest OSes aren't supported for this capability, since they don't support cloud-init.

  • Ensure that the guest OS has cloud-init installed. Most recent Linux OSes include cloud-init.

The following sections describe how to specify startup routines in the VM manifest with either the cloud-init API or startup scripts.

Use the cloud-init API to initialize VMs

Cloud-init is commonly used for cloud instance initialization and for customizing VMs during startup. VM initialization typically involves tasks like package installations, repository setup, SSH key creation, writing data out to files, and setting up other aspects of your VM. You incorporate cloud-init configuration YAML into the VirtualMachine custom resource with the spec.cloudInit field. When your VM instance starts, cloud-init reads the provided data and initializes the VM accordingly.

Note the following details of our cloud-init implementation:

  • You specify cloud-init data in the VirtualMachine YAML manifest when you create or update a VM. For instructions to create a VM by applying a manifest, see Tutorial: Create and manage a Linux VM in Anthos VM Runtime.

  • We use the NoCloud data source, spec.cloudInit.noCloud, in our VM spec.

  • You specify user data and network data in separate sections in the VirtualMachine manifest. The section naming and structure depend upon the data format you decide to use.

  • You can specify cloud-init configuration information in the following data formats:

    • Clear text
    • Base64-encoded string
    • Kubernetes Secret

To help you get started, we've provided some configuration examples for common VM initialization tasks.

Cloud-init user data

Anthos VM Runtime supports cloud-init user data in cloud-config syntax, so begin your user data with #cloud-config. You can format the user data as clear text, a base64-encoded string, or a Kubernetes Secret.

For more information about user data syntax and module reference, see the cloud-init documentation.

Cloud-init user data as clear text

The following example manifest shows how to specify user data as clear text. In this case, cloud-init executes a command when the VM starts:

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userData: |
        #cloud-config
        runcmd:
          - echo hello

Cloud-init user data as a base64-encoded string

The following example shows how to specify user data in base64-encoded format. In this example, the user data consists of the same echo hello command as in the clear text example:

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userDataBase64: I2Nsb3VkLWNvbmZpZwpydW5jbWQ6CiAgLSBlY2hvIGhlbGxvCg==

Cloud-init user data as a Kubernetes Secret

The following example shows a YAML manifest for both a VirtualMachine and a Secret. The spec.cloudInit.noCloud.secretRef section in the VirtualMachine configuration indicates that the cloud-init user data is in a Kubernetes Secret named my-sec. The corresponding Secret configuration specifies the user data as a key-value pair. The base64-encoded value in this case is the cloud-init user data in cloud-config syntax.

In the referenced Secret, use the data key userData (shown) or userdata to specify the cloud-init user data.

In this example, the user data consists of the same echo hello command as in the clear text example:

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      secretRef:
        name: my-sec
---
apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: my-sec
data:
  userData: I2Nsb3VkLWNvbmZpZwpydW5jbWQ6CiAgLSBlY2hvIGhlbGxvCg==

If the referenced Secret isn't found or the data key userData or userdata doesn't exist in the Secret, note the following VM startup behavior:

  • For VM creation, the VM is put in an ErrorConfiguration state with a detailed reason and message.

  • In other cases, the VM continues to use the old cloud-init user data until the VM is correctly configured. As a result, guest agent enable or disable updates don't take effect until the VM is correctly configured.

To retrieve VM information, including what cloud-init user data was used, use the following command:

kubectl get vm VM_NAME -o yaml --kubeconfig KUBECONFIG_PATH

Replace the following:

  • VM_NAME: the name of your VM.

  • KUBECONFIG_PATH: the path to the kubeconfig file for the cluster containing your VM.

To retrieve the related Kubernetes warning event, use either kubectl get event or kubectl describe gvm.

Cloud-init network data

Similar to user data, you can format the network data as clear text, a base64-encoded string, or a Kubernetes Secret. Unlike user data, network data doesn't use cloud-config syntax.

When using clear text or a base64-encoded string, the maximum size allowed is 2048 bytes. If the user data size is near or greater than 2048 bytes, specify it as a Kubernetes Secret.

For more information about network data syntax and related details, see the Networking Config Version 2 in the cloud-init documentation.

Cloud-init network data as clear text

The following example manifest shows how to specify network data as clear text. In this case, cloud-init enables DHCP for all ethernet devices with names that start with an "e" (e*):

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userData: |
        #cloud-config
        runcmd:
          - echo hello
      networkData: |
        version: 2
        ethernets:
          alleths:
            match:
              name: e*
            dhcp4: true

Cloud-init network data as a base64-encoded string

The following example shows how to specify network data in base64-encoded format. In this example, the network data consists of the same DHCP configuration specified in the clear text example:

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      networkDataBase64: dmVyc2lvbjogMgpldGhlcm5ldHM6CiAgYWxsZXRoczoKICAgIG1hdGNoOgogICAgICBuYW1lOiBlKgogICAgZGhjcDQ6IHRydWUK

Cloud-init network data as a Kubernetes Secret

The following example shows a YAML manifest for both a VirtualMachine and a Secret. The spec.cloudInit.noCloud.networkDataSecretRef section in the VirtualMachine configuration indicates that the cloud-init network data is in a Kubernetes Secret named my-sec. The corresponding Secret configuration specifies the network data as a key-value pair. The base64-encoded value in this case is the cloud-init network data.

In the referenced Secret, use the data key networkData (shown) or networkdata to specify the cloud-init network data.

In this example, the network data consists of the same DHCP configuration specified in the clear text example:

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      networkDataSecretRef:
        name: my-sec
---
apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: my-sec
data:
  networkData: dmVyc2lvbjogMgpldGhlcm5ldHM6CiAgYWxsZXRoczoKICAgIG1hdGNoOgogICAgICBuYW1lOiBlKgogICAgZGhjcDQ6IHRydWUK

Cloud-init examples

The following sections contain clear text examples of some common use cases for VM initialization with cloud-init:

Configure authorized SSH keys

The following user data example assigns the authorized SSH key ssh-rsa AAAAB3NzaK8L93bWxnyp to the default user.

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userData: |
        #cloud-config
        ssh_authorized_keys:
          - ssh-rsa AAAAB3NzaK8L93bWxnyp

Add a new user

The following user data example creates a user test and gives test full sudo access. This example assigns the user a non-expiring password of pwd.

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userData: |
        #cloud-config
        users:
        - default
        - name: test
          sudo: ALL=(ALL) NOPASSWD:ALL
        chpasswd:
          list: |
            test:pwd
          expire: False

Run commands on the first startup

The following user data example runs an echo command and an ls command. You can use commands to install packages and more when your VM starts.

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userData: |
        #cloud-config
        runcmd:
          - [ echo, hello ]
          - [ ls, -l, / ]

Write files

The following user data example writes a bash script to the file test in the /var/lib/google directory of your VM. The cloud-init directives set the file permissions to read, write, and execute (0744) for the file owner.

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  cloudInit:
    noCloud:
      userData: |
        #cloud-config
        write_files:
        - path: /var/lib/google/test
          permissions: 0744
          content: |
            #!/bin/bash
            echo hello

Troubleshooting cloud-init

If you encounter issues with your VM initialization and you're using cloud-init, check the following cloud-init logs in your VM:

  • /var/log/cloud-init.log: By default, cloud-init writes all events with a level of DEBUG or higher to this log.

  • /var/log/cloud-init-output.log: By default, cloud-init directs both stdout and stderr from all cloud-init stages to this log.

Use startup scripts to initialize VMs

Startup scripts perform tasks during the startup process of a virtual machine (VM) instance. You can specify one or more scripts in the spec.startupScripts section of the VirtualMachine spec. Startup scripts can be used to initialize your VM. VM initialization typically involves tasks like package installations, repository setup, SSH key creation, writing data out to files, and setting up other aspects of your VM.

Note the following details for startup scripts:

  • You specify startup scripts in the VirtualMachine YAML manifest when you create or update a VM. For instructions to create a VM by applying a manifest, see Tutorial: Create and manage a Linux VM in Anthos VM Runtime.

  • Specified scripts run every time the VM starts.

  • Include #!/bin/... at the top of the script to indicate the script interpreter. For example, include #!/bin/bash to execute the script with the Bash shell.

  • You can't specify both cloud-init API directives (spec.cloudInit) and startup scripts (spec.startupScripts) in the same VirtualMachine manifest.

Script formats

You can specify startup scripts in the following data formats:

  • Clear text
  • Base64-encoded string
  • Kubernetes Secret

Note the following rules for working with different script formats:

  • When using clear text or a base64-encoded string, the maximum size allowed for script contents is 2048 bytes. If your script content size is near or greater than 2048 bytes, specify scripts as a Kubernetes Secret.

  • When using a Kubernetes Secret, use the data key script in the referenced Secret to specify the script content.

  • If a referenced Secret isn't found or the data key script doesn't exist in the referenced Secret, the VM continues to run the script. The VM doesn't, however, write or update the script content. In this case, you can find the Kubernetes warning event with either kubectl get event or kubectl describe gvm.

The following sample VirtualMachine YAML manifest contains three scripts, one in each of the supported formats. In this case, each script runs the echo hello command shown in myscript1, the clear text example.

apiVersion: vm.cluster.gke.io/v1
kind: VirtualMachine
metadata:
  name: "my-vm"
spec:
  ...
  startupScripts:
  - name: myscript1
    script: |
      #!/bin/bash
      echo hello
  - name: myscript2
    scriptBase64: IyEvYmluL2Jhc2gKICAgICAgZWNobyBoZWxsbwo=
  - name: myscript3
    scriptSecretRef:
      name: my-sec
---
apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: my-sec
data:
  script: IyEvYmluL2Jhc2gKICAgICAgZWNobyBoZWxsbwo=

Script troubleshooting

To check the script results or logs, run the following command:

journalctl -u cloud-final

The startup script log entries begin with the following text:

started to run the command /var/lib/google/startup-scripts/SCRIPT_NAME ...

The log entry includes SCRIPT_NAME, the name of the startup script.