Sensu is an open source monitoring tool that is capable of monitoring public, private, hybrid cloud, and container-based Infrastructure environments. Sensu has been designed to be simple, scalable and malleable framework that enables you to customize monitoring to meet the business needs. This guide will walk you through the installation of Sensu Go Monitoring Tool on CentOS 8 / RHEL 8 Linux machine.

Sensu Architecture

<img alt="https://kirelos.com/wp-content/uploads/2020/05/echo/sensu-diagram.gif" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/sensu-diagram.gif" src="data:image/svg xml,”>

Sensu works in a Server-Client model where all systems to be monitored runs a sensu client software. This client application is responsible for executing local checks, managing client subscription and registration, and fulfilling checks requested by the Sensu Server.

Install Sensu Go on CentOS 8 / RHEL 8

There are three main sections of Sensu monitoring tool.

<img alt="Sensu architecture diagram" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/install-sensu.png" ezimgfmt="rs rscb8 src ng ngcb8" src="data:image/svg xml,”>

Step 1: Install Sensu Backend on CentOS 8 / RHEL 8

Add the backend repository:

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

If repository configuration was successful the output will look like below.

Complete!
Generating yum cache for sensu_stable...
Importing GPG key 0x0A3F7426:
 Userid     : "https://packagecloud.io/sensu/stable (https://packagecloud.io/docs#gpg_signing) <[email protected]>"
 Fingerprint: CB16 05C4 E988 C91F 4382 49E3 A5BC 3FB7 0A3F 7426
 From       : https://packagecloud.io/sensu/stable/gpgkey
Generating yum cache for sensu_stable-source...

The repository is setup! You can now install packages.
..

After repository addition, install Sensu backend on CentOS 8 / RHEL 8:

sudo yum install sensu-go-backend

Accept installation prompt:

Dependencies resolved.
========================================================================================================================================================
 Package                                 Architecture                  Version                                Repository                           Size
========================================================================================================================================================
Installing:
 sensu-go-backend                        x86_64                        5.20.1-12427                           sensu_stable                         14 M

Transaction Summary
========================================================================================================================================================
Install  1 Package

Total download size: 14 M
Installed size: 38 M
Is this ok [y/N]: y

Step 2: Configure Sensu Backend on CentOS 8 / RHEL 8

Copy the config template from the docs:

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

Edit it to your liking:

sudo vi /etc/sensu/backend.yml

This is how my configuration looks like:

---
# Sensu backend configuration

# backend configuration
state-dir: "https://computingforgeeks.com/var/lib/sensu/sensu-backend"
cache-dir: "https://computingforgeeks.com/var/cache/sensu/sensu-backend"
config-file: "https://computingforgeeks.com/etc/sensu/backend.yml"
debug: false
log-level: "debug" # available log levels: panic, fatal, error, warn, info, debug

##
# agent configuration
##
agent-port: 8081

##
# api configuration
##
api-listen-address: "[::]:8080" # listen on all IPv4 and IPv6 addresses
#api-url: "http://localhost:8080"

##
# dashboard configuration
##
#dashboard-cert-file: "https://computingforgeeks.com/path/to/ssl/cert.pem"
#dashboard-key-file: "https://computingforgeeks.com/path/to/ssl/key.pem"
dashboard-host: "[::]" # listen on all IPv4 and IPv6 addresses
dashboard-port: 3000

##
# ssl configuration
##
#cert-file: "https://computingforgeeks.com/path/to/ssl/cert.pem"
#key-file: "https://computingforgeeks.com/path/to/ssl/key.pem"
#trusted-ca-file: "https://computingforgeeks.com/path/to/trusted-certificate-authorities.pem"
#insecure-skip-tls-verify: false

##
# store configuration
##
#etcd-advertise-client-urls: "http://localhost:2379"
#etcd-cert-file: "https://computingforgeeks.com/path/to/ssl/cert.pem"
#etcd-client-cert-auth: false
#etcd-initial-advertise-peer-urls: "http://127.0.0.1:2380"
#etcd-initial-cluster: "default=http://127.0.0.1:2380"
#etcd-initial-cluster-state: "new" # new or existing
#etcd-initial-cluster-token: "sensu"
#etcd-key-file: "https://computingforgeeks.com/path/to/ssl/key.pem"
#etcd-listen-client-urls: "http://127.0.0.1:2379"
#etcd-listen-peer-urls: "http://127.0.0.1:2380"
#etcd-name: "default"
#etcd-peer-cert-file: "https://computingforgeeks.com/path/to/ssl/cert.pem"
#etcd-peer-client-cert-auth: false
#etcd-peer-key-file: "https://computingforgeeks.com/path/to/ssl/key.pem"
#etcd-peer-trusted-ca-file: "https://computingforgeeks.com/path/to/ssl/key.pem"
#etcd-trusted-ca-file: "https://computingforgeeks.com/path/to/ssl/key.pem"
#no-embed-etcd: false
#etcd-cipher-suits
#  - TLS_EXAMPLE

For a complete list of configuration options, see the backend reference.

Start Sensu backend service:

sudo systemctl enable --now  sensu-backend

Check service status:

systemctl status sensu-backend
● sensu-backend.service - The Sensu Backend service.
   Loaded: loaded (/usr/lib/systemd/system/sensu-backend.service; enabled; vendor preset: disabled)
   Active: active (running) since Tue 2020-05-19 21:45:05 CEST; 14s ago
 Main PID: 2194 (sensu-backend)
    Tasks: 11 (limit: 26213)
   Memory: 25.8M
   CGroup: /system.slice/sensu-backend.service
           └─2194 /usr/sbin/sensu-backend start -c /etc/sensu/backend.yml

May 19 21:45:11 cent8.computingforgeeks.com sensu-backend[2194]: {"backend_id":"861176a0-1874-4007-be62-c41f1b048dfe","component":"metricsd","level":"d>
May 19 21:45:12 cent8.computingforgeeks.com sensu-backend[2194]: {"backend_id":"861176a0-1874-4007-be62-c41f1b048dfe","component":"metricsd","level":"d>
May 19 21:45:13 cent8.computingforgeeks.com sensu-backend[2194]: {"backend_id":"861176a0-1874-4007-be62-c41f1b048dfe","component":"metricsd","level":"d>
May 19 21:45:16 cent8.computingforgeeks.com sensu-backend[2194]: {"component":"cache","level":"debug","msg":"rebuilding the cache for resource type *v2>
May 19 21:45:16 cent8.computingforgeeks.com sensu-backend[2194]: {"component":"cache","level":"debug","msg":"rebuilding the cache for resource type *v2>
May 19 21:45:16 cent8.computingforgeeks.com sensu-backend[2194]: {"component":"cache","level":"debug","msg":"rebuilding the cache for resource type *v2>
May 19 21:45:16 cent8.computingforgeeks.com sensu-backend[2194]: {"component":"tessend","level":"debug","metric_name":"auth_provider_count","metric_val>
May 19 21:45:16 cent8.computingforgeeks.com sensu-backend[2194]: {"backend_id":"861176a0-1874-4007-be62-c41f1b048dfe","component":"metricsd","level":"d>
May 19 21:45:17 cent8.computingforgeeks.com sensu-backend[2194]: {"backend_id":"861176a0-1874-4007-be62-c41f1b048dfe","component":"metricsd","level":"d>
May 19 21:45:18 cent8.computingforgeeks.com sensu-backend[2194]: {"backend_id":"861176a0-1874-4007-be62-c41f1b048dfe","component":"metricsd","level":"d>

Step 3: Initialize Sensu Backend

You now need to set up your Sensu administrator username and password. Run the following command to initialize the Sensu backend:

export SENSU_BACKEND_CLUSTER_ADMIN_USERNAME=admin
export [email protected]
sensu-backend init

Command execution output:

{"component":"backend.seeds","level":"info","msg":"seeding etcd store with intial data","time":"2020-05-19T21:50:07 02:00"}

You can also run the sensu-backend init command in interactive mode if you prefer to respond to prompts for your username and password:

sensu-backend init --interactive

More details abou the sensu-backend init, see the backend reference documentation.

Step 4: Access Sensu Dashboard

The Sensu web UI provides a unified view of your monitoring events and user-friendly tools to reduce alert fatigue.

Confirm the UI service port is up.

$ sudo ss -tunelp | grep 3000
tcp   LISTEN  0       128                         *:3000                *:*      users:(("sensu-backend",pid=2194,fd=18)) uid:994 ino:27800 sk:a v6only:0

Check if the backend is up and running by querying API health:

$ curl http://127.0.0.1:8080/health
{"Alarms":null,"ClusterHealth":[{"MemberID":9882886658148554927,"MemberIDHex":"8927110dc66458af","Name":"default","Err":"","Healthy":true}],"Header":{"cluster_id":4255616304056076734,"member_id":9882886658148554927,"raft_term":2}}

If you have active firewall service, allow port 3000.

sudo firewall-cmd --add-port=3000/tcp --permanent
sudo firewall-cmd --reload

Open your browser and access Sensu dashboard on http://localhost:3000 or http://server_ip_or_hostname:3000.

<img alt="" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/install-sensu-centos-8-01-1024×635.png" data-ez ezimgfmt="rs rscb8 src ng ngcb8 srcset" src="data:image/svg xml,”>

Login with credentials set earlier.

<img alt="" data-ezsrc="https://kirelos.com/wp-content/uploads/2020/05/echo/install-sensu-centos-8-02-1024×417.png" data-ez ezimgfmt="rs rscb8 src ng ngcb8 srcset" src="data:image/svg xml,”>

Our next guides will cover installation of Sensu Agents and sensuctl command line tool.

Reference:

More on monitoring:

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How to install Cacti on RHEL / CentOS 8

How to Install Zabbix Server on RHEL / CentOS 8

How to Install Netdata on RHEL / CentOS 8

Install and Configure Telegraf on RHEL / CentOS 8

How to Install Prometheus on RHEL / CentOS 8

How to Install Grafana on RHEL 8

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