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Lesson 3: Using the Sensu CLI

Goals

In this lesson we will introduce the sensuctl command-line tool. You will learn how to install and configure the tool, then practice performing some essential operations.

This lesson is intended for operators of Sensu and assumes you have set up a local workshop environment.

The sensuctl Command Line Interface (CLI)

The sensuctl CLI, short for Sensu Control, gives you full control of your Sensu pipeline from a command-line environment. You can use sensuctl interactively in a shell, or script it as part of an automated solution.

The sensuctl tool is available for Linux, macOS, and Windows.

EXERCISE 1: Install the sensuctl CLI

Scenario

You want to view and manage resources in Sensu from a command-line environment or in an automated script.

Solution

Install the sensuctl CLI tool.

First, we will configure some helpful environment variables, download the sensuctl binary, then install it.

Steps

  1. Configure Environment Variables.

    The workshop repository includes platform-specific files that export some environment variables which we will use throughout the workshop. The exercises assume you are in a shell that has these variables configured.

    When you open a new shell environment, export the variables using one of the following commands:

    Mac and Linux:

    source .envrc

    Windows (Powershell):

    . .\.envrc.ps1

  2. Verify Your Environment.

    The Sensu-specific environment variables are prefixed with SENSU. You can verify that you have the Sensu environment variables set up correctly by running one of these commands:

    Mac and Linux:

    env | grep SENSU

    Windows (Powershell):

    Get-ChildItem env: | Out-String -Stream | Select-String -Pattern SENSU

    The output should include a value for SENSU_VERSION (i.e. a release version such as 6.2.7).

    Example Output:

    SENSU_VERSION=6.5.1
SENSU_BUILD=5325
SENSU_BACKEND_HOST=127.0.0.1
SENSU_NAMESPACE=default
SENSU_USER=sensu
SENSU_PASSWORD=sensu
SENSU_BACKEND_URL=ws://127.0.0.1:8081
SENSU_API_URL=http://127.0.0.1:8080

  3. Download and Install sensuctl.

    Download the platform-specific archive from Sensu's official release location. Unpack the archive into a standard location.

    Mac:

    curl -LO "https://s3-us-west-2.amazonaws.com/sensu.io/sensu-go/${SENSU_VERSION}/sensu-go_${SENSU_VERSION}_darwin_amd64.tar.gz"
sudo tar -xzf "sensu-go_${SENSU_VERSION}_darwin_amd64.tar.gz" -C /usr/local/bin/

    Linux:

    curl -LO "https://s3-us-west-2.amazonaws.com/sensu.io/sensu-go/${SENSU_VERSION}/sensu-go_${SENSU_VERSION}_linux_amd64.tar.gz"
tar -xzf "sensu-go_${SENSU_VERSION}_linux_amd64.tar.gz" -C /usr/local/bin/

    Windows (Powershell):

    Invoke-WebRequest `
  -Uri "https://s3-us-west-2.amazonaws.com/sensu.io/sensu-go/${Env:SENSU_VERSION}/sensu-go_${Env:SENSU_VERSION}_windows_amd64.zip" `
  -OutFile "${Env:UserProfile}\sensu-go_${Env:SENSU_VERSION}_windows_amd64.zip"
Expand-Archive `
  -LiteralPath "${Env:UserProfile}\sensu-go_${Env:SENSU_VERSION}_windows_amd64.zip" `
  -DestinationPath "${Env:UserProfile}\Sensu\bin"
${Env:Path} += ";${Env:UserProfile}\Sensu\bin"

    NOTE: On Unix-like systems /usr/local/bin is the standard location for binaries shared between multiple users. On macOS, the default permissions for /usr/local/bin require the used of sudo. However, any location that is on your $PATH will work (i.e. ~/bin). On Windows systems we create a new location specifically for Sensu, then add it to the path.

Configuration Options

Sensu is an API

Sensu has an API-based architecture. Everything that happens on the platform is done by interacting with one or more APIs. The primary function of sensuctl is to manage Sensu resources. It does this by calling Sensu's API to create, read, update, and delete (CRUD) resources like events, checks, and handlers.

Since sensuctl is an API client, it requires some configuration settings to get started.

Sensu Backend Url

Sensu's API is provided by a backend. The backend URL is the adress and port of the backend you want to manage.

For this workshop, we will be using the URL http://127.0.0.1:8080.

Authentication Type

Because all access to the Sensu API requires authentication, sensuctl must be configured with login credentials. Sensu supports both username/password and OIDC-based authentication.

For this workshop, we will be using the username sensu and the password sensu.

Namespaces

Sensu resources can be organized by namespace. This is helpful in complex infrastructures where there are many systems to observe and manage.

For this workshop, we will be using the default namespace.

Output Format

Since sensuctl can be used both interactively and in automated scripts, there are a variety of output options available. The default tabular output mode is a compact and human-readable format.

For this workshop, we will be using the tabular output mode.

EXERCISE 2: Configure the sensuctl CLI

Scenario

You've just installed sensuctl and need to configure it to interact with a Sensu backend API.

Solution

Run the sensuctl configure command. This interactive command will prompt you for all the necessary configuration variables.

Steps

  1. Run the sensuctl configure Command.

    The sensuctl configure command will prompt you to provide the preferred authentication method, backend URL, namespace, output format, username, and password.

    sensuctl configure

    For this workshop, we will use the following options:

    • Authentication method: username/password
    • Sensu Backend URL: http://127.0.0.1:8080
    • Namespace: default
    • Preferred output format: tabular
    • Username: sensu
    • Password: sensu

  2. Verify the sensuctl Configuration.

    You should now have successfully configured sensuctl.

    To confirm, run a sensuctl command to verify the configuration:

    sensuctl config view

    Example Output:

    === Active Configuration
API URL:                  http://127.0.0.1:8080
Namespace:                default
Format:                   tabular
Timeout:                  15s
Username:                 sensu
JWT Expiration Timestamp: 1234567890

PROTIP: Certain sensuctl commands support a non-interactive mode. This is helpful when using sensuctl in an automated context like a CI/CD pipeline.

For example, the sensuctl configure command can be run non-interactively using the -n option.

Example: Non-interactive use of sensuctl configure

$ sensuctl configure -n \
  --api-url http://127.0.0.1:8080 \
  --namespace default \
  --username sensu \
  --password ${SENSU_PASSWORD} \
  --format json

API Keys

Another way to authenticate requests is to use an api key. API keys allow automated components access to the API without the need for usernames and passwords.

Many of the exercises in this workshop will require an API key, so let's create one now.

EXERCISE 3: Create an API Key

Scenario

You want to use tools like curl and sensuctl to create and manage resources, but you prefer to use revocable API keys instead of usernames and passwords.

Solution

Create an API key using sensuctl api-key grant. This will create a user-specific key that can be used in an authorization header of an API request.

This key can also be used with any sensuctl command by adding the --api-key option.

Steps

  1. Create an API Key Using the sensuctl api-key grant Command.

    API keys are user-specfic, so we need to specify the user. This key will be created for the sensu user.

    sensuctl api-key grant sensu

    Example Output:

    Created: /api/core/v2/apikeys/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

  2. Save the API Key in the SENSU_API_KEY Environment Variable.

    For this workshop, we want to save the API key in an environment variable for use in future exercises.

    1. Copy the xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx part of the output onto the clipboard (without the /api/core/v2/apikeys/ portion).

    2. Modify the .envrc or .envrc.ps1, replacing the value for SENSU_API_KEY with the key we just copied, then uncomment the line.

      When complete, your file should have a line like this:

      Mac and Linux users (.envrc):

      export SENSU_API_KEY=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

      Windows users (.envrc.ps1):

      ${Env:SENSU_API_KEY}="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"

  3. Reload the Environment Variables.

    Mac and Linux:

    source .envrc

    Windows (Powershell):

    . .\.envrc.ps1

  4. Verify that the SENSU_API_KEY environment variable is set:

    Mac and Linux:

    echo $SENSU_API_KEY

    Windows (Powershell):

    $env:SENSU_API_KEY

PROTIP: If you like to automate things like this using shell scripts, you might already be thinking about how to parse the output of the sensuctl api-key grant command.

The following example should do the trick for Mac and Linux users:

Example: Parsing an API key using awk

export SENSU_API_KEY=$(sensuctl api-key grant sensu | awk -F "/" '{print $NF}')

Listing and Viewing Resources

One of the common uses of sensuctl is to list and view resources like namespaces, users, and entities.

EXERCISE 4: List Sensu Resources

Scenario

You want to explore the resources under management by Sensu.

Solution

To see a list, use the sensuctl <resource_type> list command pattern. The list subcommand is available for nearly all resources, including common resources like namespaces, users, and entities.

Steps

  1. Use the sensuctl namespace list Command to Get a List of Namespaces.

    sensuctl namespace list

    Example Output:

       Name
 ─────────
  default
  trainee

  2. Use the sensuctl user list Command to Get a List of Users.

    sensuctl user list

    Example Output:

      Username           Groups            Enabled
 ────────── ───────────────────────── ─────────
  agent      system:agents             true
  sensu      cluster-admins            true
  trainee    trainee,trainee:trainee   true

PROTIP: Want to explore what sensuctl can do? Try using the --help option to show a list of commands. This option is available on all commands and subcommands.

Inventory Management

One of the use cases for Sensu is endpoint management. The infrastructure Sensu is monitoring can be listed using sensuctl, creating a real-time "inventory of nodes".

Nodes are represented as entities, and they either have an agent running locally, or are proxying observability data through an agent running elsewhere.

The commands sensuctl entity list and sensuctl entity info <entity_id> are used to list and inspect entities.

EXERCISE 5: List an Inventory of Nodes

Scenario

You have a large inventory of nodes and you want to view a real-time list of those entities. You also want to automate some tasks based on that list, but need some detailed information about the node in JSON format.

Solution

To view a list of nodes, use the sensuctl entity list command. Individual node information can be viewed using the sensuctl entity info <entity_id> command. In automated scenarios, adding the --format json option will output the information in JSON format.

Steps

  1. List Entities Under Management by Sensu.

    To get a real-time list of entities, run sensuctl entity list.

    sensuctl entity list

    Example Output:

               ID         Class      OS                       Subscriptions                              Last Seen
 ──────────────── ─────── ────────── ───────────────────────────────────────────────── ───────────────────────────────
  0ed711859366     agent   linux      system/linux,workshop,devel,entity:0ed711859366   2021-09-15 17:18:18 -0700 PDT
  learn.sensu.io   proxy   Workshop   entity:learn.sensu.io                             N/A

  2. Show Detailed Entity Information.

    To get detailed information about an entity, run sensuctl entity info <entity_id>.

    sensuctl entity info learn.sensu.io

    Example Output:

    === learn.sensu.io
Name:                   learn.sensu.io
Entity Class:           proxy
Subscriptions:          entity:learn.sensu.io, workshop-test
Last Seen:              N/A
Hostname:               learn.sensu.io
OS:                     Workshop
Platform:               Sensu Go
Platform Family:        Training
Platform Version:       6.2.7
Auto-Deregistration:    true
Deregistration Handler:

  3. Output Entity Information in JSON Format.

    Entity information is commonly used in automation scenarios, such as scripts or CI/CD workflows. In those situations it you may wish to output this information in a structured format like JSON.

    sensuctl entity info learn.sensu.io --format json

    Example Output:

    {
  "entity_class": "proxy",
  "system": {
    "hostname": "learn.sensu.io",
    "os": "Workshop",
    "platform": "Sensu Go",
    "platform_family": "Training",
    "platform_version": "6.2.7",
    "network": {
      "interfaces": [
        {
          "name": "lo",
          "mac": "00:00:00:00:00:00",
          "addresses": [
            "127.0.0.1/8",
            "::1/128"
          ]
        },
        {
          "name": "eth0",
          "mac": "00:00:00:00:00:00",
          "addresses": [
            "10.0.0.1/8"
          ]
        }
      ]
    },
    "arch": "arm",
    "libc_type": "",
    "vm_system": "",
    "vm_role": "",
    "cloud_provider": "",
    "processes": null
  },
  "subscriptions": [
    "entity:learn.sensu.io",
    "workshop-test"
  ],
  "last_seen": 0,
  "deregister": true,
  "deregistration": {},
  "user": "workshop",
  "metadata": {
    "name": "learn.sensu.io",
    "namespace": "default",
    "labels": {
      "app": "workshop"
    },
    "created_by": "sensu"
  },
  "sensu_agent_version": ""
}

    PROTIP: The ability to output JSON is especially powerful when combined with tools like jq. For example, let's try extracting the system platform version that is running on the system that this event came from:

    sensuctl entity info learn.sensu.io --format json | jq .system.platform_version

Monitoring as Code

The sensuctl monitoring-as-code workflow manages resource configurations using plain-text formats like YAML and JSON.

Managing resources follows these basic steps:

  1. Resource configurations are defined in a YAML or JSON file.
  2. The sensuctl create command reads the resource configuration from the file, then pushes that configuration to the backend API where the resource is created.
  3. The file can then be saved to a file within a source code repository.
  4. Later, the file can be modified and sensuctl create is used to update the resource.

You can also use the sensuctl dump command to export a resource to a file, or add the --format option to a sensuctl entity info command to output the resource in a structured format.

These features together enable Sensu's monitoring-as-code workflow.

EXERCISE 6: Exporting and Updating Resource Configurations

Scenario

You have an entity in a running Sensu environment but don't have a YAML file that describes it. You'd like to save the resource to a file so you can modify the configuration, and store that configuration to a code repository.

Solution

To accomplish this, we will use the sensuctl entity info command with the --format yaml option to output an existing resource to YAML. Once we have that YAML file, we can modify the configuration, then update the resource configuration using sensuctl create.

Steps

  1. Export an Entity Configuration in YAML Format.

    Use the sensuctl entity info command with the --format yaml option. Pipe the output to a file named entity.yaml.

    sensuctl entity info learn.sensu.io --format yaml > entity.yaml

    Example Output: entity.yaml

    type: Entity
api_version: core/v2
metadata:
  created_by: sensu
  labels:
    app: workshop
  name: learn.sensu.io
  namespace: default
spec:
  deregister: true
  deregistration: {}
  entity_class: proxy
  last_seen: 0
  sensu_agent_version: ""
  subscriptions:
  - entity:learn.sensu.io
  system:
    arch: arm
    cloud_provider: ""
    hostname: learn.sensu.io
    libc_type: ""
    network:
      interfaces:
      - addresses:
        - 127.0.0.1/8
        - ::1/128
        mac: "00:00:00:00:00:00"
        name: lo
      - addresses:
        - 10.0.0.1/8
        mac: "00:00:00:00:00:00"
        name: eth0
    os: Workshop
    platform: Sensu Go
    platform_family: Training
    platform_version: 6.2.7
    processes: null
    vm_role: ""
    vm_system: ""
  user: workshop

  2. Modify the Resource Configuration.

    Using a text editor, change the subscriptions list, adding a new item workshop-test.

    Example: entity.yaml

    type: Entity
api_version: core/v2
metadata:
  created_by: sensu
  labels:
    app: workshop
  name: learn.sensu.io
  namespace: default
  spec:
    deregister: true
    deregistration: {}
    entity_class: proxy
    last_seen: 0
    sensu_agent_version: ""
    subscriptions:
    - entity:learn.sensu.ioi
    - workshop-test
    system:
[..clipped..]

  3. Update the Running Resource Configuration.

    Update the running entity configuration using sensuctl create. The -f option specifies the YAML file to read from.

    If the specified resource doesn't exist, the sensuctl create command will create it. However, if it already exists, the command will update it.

    sensuctl create -f entity.yaml

  4. Verify the Updated Configuration.

    View the updated configuration by running sensuctl entity info.

    sensuctl entity info learn.sensu.io

    Example Output:

    === learn.sensu.io
Name:                   learn.sensu.io
Entity Class:           proxy
Subscriptions:          entity:learn.sensu.io, workshop-test
Last Seen:              N/A
Hostname:               learn.sensu.io
OS:                     Workshop
Platform:               Sensu Go
Platform Family:        Training
Platform Version:       6.2.7
Auto-Deregistration:    true
Deregistration Handler:

    If you now have workshop-test listed in the Subscriptions value, the update was successful!

Discussion

In this lesson, you learned how to install and configure the sensuctl CLI tool, create an API key, and how to explore and manage resources in Sensu.

Sensu is an API, sensuctl is the Client

At the core of these operations is the Sensu API. In fact, sensuctl can be thought of as a client for the Sensu API, making it easier to perform common tasks from the command line. These same tasks could have been perfomed with curl or any other system that can make HTTP requests.

Sensu's API-based design is key to enabling monitoring-as-code workflows, and allows for extensive customization via scripting and automation.

Sensu Web App

For those who prefer a browser-based user experience, the Sensu Web App can perform many of the same tasks. It interacts with the same APIs and gives you some powerful visualization and exploration tools. Learn more about the Sensu Web App in Lesson X.

Learn More

Next Steps

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Lesson 4: Introduction to Handlers