How to Install Sensu Monitoring Solution on Rocky Linux 9

Sensu is an open-source infrastructure and application monitoring system designed for container and non-container monitoring and multi-cloud infrastructure.

Sensu is a scalable, secure, integrated monitoring solution for your technology and server infrastructure. It can be used to monitor servers, application health, and services, and send alerts notification to multiple targets with third-party integration.

In this tutorial, you will install Sensu Monitoring Solution on a Rocky Linux 9 server. In addition to that, you will also install and set up Sensuctl which allows you to manage Sensu via the command line terminal.

Through the end of this tutorial, you will also install Sensu Agent on RHEL-based distributions and Debian-based distributions. Then, you will set up checks for monitoring servers via Sensu Agent.

Prerequistes

To follow this tutorial, you will need the following requirements:

• A Linux server with Rocky Linux 9.
• A non-root user with sudo/root administrator privileges.
• An SELinux is running on permissive mode.

As for the target monitoring server, this example uses Rocky Linux and Debian servers. Below are the details servers that will be used for the demonstration:

Host          IP Address        Used as
-----------------------------------------------
sensu-rock    192.168.5.45    Sensu Go Backend
RPM-OS        192.168.5.80    Sensu Go Agent
DEB-OS        192.168.5.85    Sensu Go Agent

That's it. You're good to go to start the Sensu installation.

Setting up Repository

The first thing you will do is enable CRB (Code Ready Builder) repository, add the EPEL (Extra Package for Enterprise Linux) repository, then you will add the Sensu repository via packagecloud.io.

On Rocky Linux 9, the crb repository is equivalent to PowerTools which is available on CentOS. Run the following dnf command to enable the crb repository and install the EPEL repository.

sudo dnf config-manager --set-enabled crb
sudo dnf install epel-release

Once crb is enabled and the EPEL repository installed, run the following command to add the Sensu repository to your Rocky Linux server. This will set up the Sensu repository on your system automatically, and you'll be using the Sensu repository from the stable branch.

curl -s https://packagecloud.io/install/repositories/sensu/stable/script.rpm.sh | sudo bash

Verify the list of enabled repositories on your system by entering the dnf command below. You should receive an out that the crb, epel, and sensu_stable repositories are added to your Rocky Linux system.

sudo dnf repolist

Now that you've added the necessary repositories, you're ready to start Sensu installation.

Installing Sensu Go Backend

Sensu is a complete solution for monitoring at scale that can be used to monitor traditional servers, containers, applications, and/or cloud applications. Before installing Sensu, you must know that there are three components on Sensu, below is the list:

• Sensu Backend - the main component of Sensu that is powered by an embedded transport and etcd datastore. Sensu Backend exposed the WebSocket that will be used to communicate with Sensu Agent, the HTTP API that will be used to communicate with sensuctl. Also, it provides a web UI dashboard that you can access via browser.
• Sensu Agent - this is a lightweight client that will be installed and running on target servers. AN agent will generate status and metrics on the target server and send the results to the Sensu Backend via WebSocket.
• Sensu Workstation - this is the local computer on that you can install Sensuctl, or you can access Sensu Dashboard from your browser.

In this section, you will install and configure Sensu Backend on the Rocky Linux server.

Enter the following dnf command to install the 'sensu-go-backend' package to your system. When prompted, input y to confirm and press ENTER to proceed.

sudo dnf install sensu-go-backend

Once Sensu Backend is installed, download the sample configuration of Sensu Backend to '/etc/sensu/backend.yml' via curl. Then, open the downloaded file using the following nano editor command.

sudo curl -L https://docs.sensu.io/sensu-go/latest/files/backend.yml -o /etc/sensu/backend.yml
sudo nano /etc/sensu/backend.yml

Uncomment the following lines.

cache-dir: "/var/cache/sensu/sensu-backend"
config-file: "/etc/sensu/backend.yml"

log-level: "debug"
state-dir: "/var/lib/sensu/sensu-backend"

Save and close the file '/etc/sensu/backend.yml' when finished.

Next, run the following systemctl command utility to start and enable the 'sensu-backend' service. With this, the Sensu Backend should be running and will start automatically at system startup.

sudo systemctl start sensu-backend
sudo systemctl enable sensu-backend

Run the following systemctl command to verify the 'sensu-backend' service and ensure that the service is running and enabled.

sudo systemctl is-enabled sensu-backend
sudo systemctl status sensu-backend

The output 'enabled' confirms that the Sensu Backend will start automatically at system startup. And the output 'active (running)' confirms that the Sensu Backend is currently running.

Now that you've installed the Sensu backend and it's running and enabled. Next, you will initialize the Sensu admin user and verify the installation.

Configuring Sensu Go Backend

In this section, you will initialize the administrator username and password for Sensu Backend, verify the installation via curl and web browser, and open some ports via firewalld.

Run the following command to set up environment variables 'SENSU_BACKEND_CLUSTER_ADMIN_USERNAME' and 'SENSU_BACKEND_CLUSTER_ADMIN_PASSWORD'. Be sure to change the value with your username and password.

export SENSU_BACKEND_CLUSTER_ADMIN_USERNAME=adminsensu
export SENSU_BACKEND_CLUSTER_ADMIN_PASSWORD=SensuRocks

Now run the following 'sensu-backend init' command to initialize your Sensu installation. With this, your Sensu backend admin user is created.

sensu-backend init

Next, run the following command to install the 'jq' package for parsing output to json. Then, run the curl command to verify the Sensu Backend status. The HTTP API of the Sensu backend is running on the default port 8080.

sudo dnf install jq
curl -s http://127.0.0.1:8080/health | jq .

The output 'Healthy: true' confirms that the Sensu Backend is running without an error.

Before accessing the Sensu dashboard, you must open ports on firewalld.

Enter the following firewall-cmd command top some ports for Sensu Backend. Then, reload the firewalld to apply the changes.

sudo firewall-cmd --add-port={2379/tcp,2380/tcp,3000/tcp,6060/tcp,8080/tcp,8081/tcp} --permanent
sudo firewall-cmd --reload

Verify the list of open ports on firewalld via the following command.

sudo firewall-cmd --list-all

Now open your web browser and visit the server IP address followed by port 3000 (i.e: http://192.168.5.45:3000/). You should get the login page of the Sensu backend.

Log in with your username and password, then click 'SIGN-IN'.

When successful, you should get the Sensu administration dashboard.

With this, you have now installed Sensu Backend, configured the admin user and password, and also successfully logged in to the Sensu dashboard from the browser. In the next step, you will install the Sensuctl, then connect to the Sensu Backend via Sensuctl.

Installing Sensuctl Command Line

Run the following dnf command to install the Sensuctl command. When prompted, input y to confirm and press ENTER to proceed.

sudo dnf install sensu-go-cli

Once Sensuctl is installed, run the following command to verify the binary path and version of Sensuctl.

which sensuctl
sensuctl --version

The binary path of Sensuctl is available at the '/bin/sensuctl', and the installed version is v6.9.1.

Next, run the following 'sensuctl' command to configure the connection to your Sensu Backend server.

sensuctl configure

You'll now be asked about some configurations:

• Authentication method? username/password
• Sensu Backend API URL? Sensu API is running by default on http://127.0.0.1:8080
• Namespace? default
• Preferred output format? Select the output format that you want - this example is json.
• Username? admin user for sensu
• Password? password for the sensu admin user

When finished, run the below command to verify the details connection.

sensuctl config view

You'll receive the output similar to this - The Sensuctl is connected to the Sensu Backend via HTTP API that runs by default on 'http://127.0.0.1:8080'.

After configuring Sensuctl, you will now enable the auto-completion for the Sensuctl command line.

Run the following dnf command to install the 'bash-completion' package.

sudo dnf install bash-completion -y

When 'bash-completion' is installed, open the '~/.bashrc' file using the following nano editor command.

sudo nano ~/.bashrc

Add the following lines to the file. This will enable the 'bash-completion' for the root user.

if [ -f /usr/share/bash-completion/bash_completion ]; then
. /usr/share/bash-completion/bash_completion
elif [ -f /etc/bash_completion ]; then
. /etc/bash_completion
fi

source <(sensuctl completion bash)

Save and exit the file when finished.

Next, run the following command to reload the '~/.bashrc' file on your current session.

source ~/.bashrc

Verify the auto-completion by entering the 'sensuctl' command and pressing TAB.

sensuctl TAB

When successful, you should get the list of options that are available on the 'sensuctl' command.

With this, you have now installed Sensuctl, connected to the Sensu Backend server via Sensuctl, and also configured its auto-complete. Next, you will set up Sensu Agent on Rocky Linux and Debian servers.

Installing Sensu Agent

In this section, you will install and set up Sensu Agent on two different nodes. You will install Sensu Agent on RHEL-based distributions and Debian-based distributions. Then, set up the Sensu Agent to connect to the Sensu Backend server that you've installed via WebSocket.

Now, let's start.

Sensu Agent on RHEL-Based Distributions

This example uses a Rocky Linux 9 machine, which is based on RHEL or CentOS 9. To install Sensu Agent, you must add the Sensu repository and open some ports on firewalld.

Run the following firewall-cmd command to open some ports. Then, reload the firewalld to apply the changes.

sudo firewall-cmd --add-port={3030/tcp,3030/udp,3031/tcp,8125/udp} --permanent
sudo firewall-cmd --reload

Verify the list of enabled ports on firewalld via the command below.

sudo firewall-cmd --list-all

You should receive an output like this:

Next, enter the following dnf command to enable the crb repository and install the EPEL repository.

sudo dnf config-manager --set-enabled crb
sudo dnf install epel-release

Now add the Sensu repository by entering the below command. This will download and run the bash installer script that will automate the repository configuration.

curl -s https://packagecloud.io/install/repositories/sensu/stable/script.rpm.sh | sudo bash

Output:

Once the Sensu repository is added, run the following dnf command to install the 'sens-go-agent' package to your system. When prompted, input y to confirm and press ENTER to proceed.

sudo dnf install sensu-go-agent

Output:

Next, run the following command to download the Sensu Agent config file to '/etc/sensu/agent.yml'. Then, open the config file '/etc/sensu/agent.yml' using the nano editor command below.

sudo curl -L https://docs.sensu.io/sensu-go/latest/files/agent.yml -o /etc/sensu/agent.yml
sudo nano /etc/sensu/agent.yml

Uncomment the following lines and be sure to change the default 'name' with the system hostname and the 'backend-url' with the WebSockt IP address of the Sensu Backend server.

In this example, the system hostname is 'RPM-OS' and the Sensu Backend server IP address is '192.168.5.45'.

name: "RPM-OS"
namespace: "default"
...
backend-url:
  - "ws://192.168.5.45:8081"
cache-dir: "/var/cache/sensu/sensu-agent"
config-file: "/etc/sensu/agent.yml"

Save the file '/etc/sensu/agent.yml' and exit the editor when finished.

Now run the following systemctl command to start and enable the 'sensu-agent' service.

sudo systemctl start sensu-agent
sudo systemctl enable sensu-agent

An output 'Create symlink ... => ...' confirms that the Sensu Agent is enabled.