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How to Configure Nagios to Monitor a PostgreSQL 16 Database with Dashboards on Ubuntu 24.04 LTS #postgresql #postgres #nagios


This content originally appeared on DEV Community and was authored by Chitt Ranjan Mahto (Chirag)

inchirags@gmail.com Chirag PostgreSQL DBA Tutorial https://www.chirags.in

How to Configure Nagios to Monitor a PostgreSQL 16 Database with Dashboards on Ubuntu 24.04 LTS

Here’s a step-by-step guide to configure Nagios to monitor a PostgreSQL 16 database with dashboard access on Ubuntu 24.04 LTS.

🧭 Architecture

Role IP Address Description

Nagios Server 192.168.136.129 Hosts Nagios Core + Dashboards

PostgreSQL Server 192.168.136.130 PostgreSQL 16 server being monitored

Default password everywhere: admin@123

Step 1: Install PostgreSQL 16 (on 192.168.136.130)

If PostgreSQL is already installed and running, skip this step.

sudo apt update
sudo apt install postgresql-16 postgresql-contrib -y
sudo systemctl enable –now postgresql
Set password for the postgres user:

sudo -u postgres psql -c “ALTER USER postgres WITH PASSWORD ‘admin@123’;”
Step 2: Enable PostgreSQL Remote Access (on 192.168.136.130)

Edit postgresql.conf:

sudo nano /etc/postgresql/16/main/postgresql.conf
Find and change:

listen_addresses = ‘*’
Edit pg_hba.conf:

sudo nano /etc/postgresql/16/main/pg_hba.conf
Add at the end:

host all all 192.168.136.129/32 md5
Restart PostgreSQL:

sudo systemctl restart postgresql
Step 3: Create Monitoring User in PostgreSQL (on 192.168.136.130)

sudo -u postgres psql
Inside psql:

CREATE USER nagios WITH PASSWORD ‘admin@123’;
GRANT CONNECT ON DATABASE postgres TO nagios;
\q
Step 4: Install Nagios Core on Server1 (192.168.136.129)

Step 4.1: Install Dependencies

sudo apt update
sudo apt install nagios-plugins-basic nagios-plugins-standard -y
sudo apt install -y apache2 php php-gd unzip build-essential libgd-dev libapache2-mod-php \
libperl-dev libssl-dev daemon wget libnet-snmp-perl gettext
Step 4.2: Add Nagios User

sudo useradd nagios
sudo groupadd nagcmd
sudo usermod -a -G nagcmd nagios
sudo usermod -a -G nagcmd www-data
Step 4.3: Download and Compile Nagios

cd /tmp
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.5.1.tar.gz
tar xvf nagios-4.5.1.tar.gz
cd nagios-4.5.1
./configure –with-command-group=nagcmd
make all
sudo make install
sudo make install-commandmode
sudo make install-init
sudo make install-config
sudo make install-webconf
Step 4.4: Create Nagios Web User

sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Enter: admin@123

Enable Apache modules:

sudo a2enmod rewrite cgi
sudo systemctl restart apache2
Start Nagios:

sudo systemctl enable –now nagios
Step 5: Install Nagios Plugins and NRPE

On Server2 (PostgreSQL server: 192.168.136.130):

sudo apt install nagios-nrpe-server nagios-plugins -y
Allow Server1 IP in /etc/nagios/nrpe.cfg:

sudo nano /etc/nagios/nrpe.cfg
Edit:

allowed_hosts=127.0.0.1,192.168.136.129
Restart NRPE:

sudo systemctl restart nagios-nrpe-server
Step 6: Install PostgreSQL Plugin for Nagios (192.168.136.129)

On Server1 (Nagios):

cd /usr/local/nagios/libexec
wget https://raw.githubusercontent.com/bucardo/check_postgres/master/check_postgres.pl
chmod +x check_postgres.pl
Plugins get installed to /usr/local/nagios/libexec

Step 7: Configure Nagios to Monitor PostgreSQL

Edit command file:

sudo nano /usr/local/nagios/etc/objects/commands.cfg
Add:

define command {
command_name check_postgres_connection
command_line /usr/local/nagios/libexec/check_postgres.pl –action=connection –dbhost=192.168.136.130 –dbuser=nagios –dbpass=admin@123
}

define command {
command_name check_postgres_backends
command_line /usr/bin/perl /usr/local/nagios/libexec/check_postgres.pl –action=backends –dbhost=$ARG1$ –dbuser=$ARG2$ –dbpass=$ARG3$ –warning=50 –critical=100
}

define command {
command_name check_postgres_locks
command_line /usr/bin/perl /usr/local/nagios/libexec/check_postgres.pl –action=locks –dbhost=$ARG1$ –dbuser=$ARG2$ –dbpass=$ARG3$ –warning=10 –critical=20
}

define command {
command_name check_postgres_replication_lag
command_line /usr/bin/perl /usr/local/nagios/libexec/check_postgres.pl –action=replication_lag –dbhost=$ARG1$ –dbuser=$ARG2$ –dbpass=$ARG3$ –warning=5 –critical=10
}
Edit Nagios configuration to add host/service:

mkdir -p /usr/local/nagios/etc/servers/
sudo nano /usr/local/nagios/etc/servers/postgres.cfg
Add:

define host {
use linux-server
host_name server2
alias PostgreSQL Server
address 192.168.136.130
}

define service {
use generic-service
host_name server2
service_description PostgreSQL Connection
check_command check_postgres_connection
}

define service {
use generic-service
host_name server2
service_description PostgreSQL Backends
check_command check_postgres_backends!192.168.136.130!nagios!admin@123
}

define service {
use generic-service
host_name server2
service_description PostgreSQL Locks
check_command check_postgres_locks!192.168.136.130!nagios!admin@123
}

define service {
use generic-service
host_name server2
service_description PostgreSQL Replication Lag
check_command check_postgres_replication_lag!192.168.136.130!nagios!admin@123
}
Include this config in nagios.cfg:

sudo nano /usr/local/nagios/etc/nagios.cfg
Add:

cfg_dir=/usr/local/nagios/etc/servers
Validate Configuration:

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
Output:

Total Warnings: 0

Total Errors: 0

–Create directory:

—sudo mkdir -p /usr/local/nagios/etc/servers

—sudo mv /usr/local/nagios/etc/servers/postgres.cfg /usr/local/nagios/etc/servers/

Step 8: Restart Nagios

sudo systemctl restart nagios
Step 9: Access Nagios Dashboard

sudo ufw allow 80/tcp
sudo ufw reload
Visit:

🔗 http://192.168.136.129/nagios
Login:

Username: nagiosadmin

Password: admin@123

Step 10: Monitor Additional Metrics (Optional)

Go to Current Status → Services

You should now see:

PostgreSQL Connection

PostgreSQL Backends

PostgreSQL Locks

PostgreSQL Replication Lag

You can monitor more metrics like:

--action=locks

--action=bloat

--action=backends

--action=connection

(Adjust check_command accordingly)

Step 11: Test the connection in Server1

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
If you see “Total Warnings=0, Total Errors=0”, config is fine.

❌ If not, fix the path (cfg_dir) in nagios.cfg

Log file Path:

sudo tail -f /usr/local/nagios/var/nagios.log
Remove the bad one

sudo rm -f /usr/local/nagios/libexec/check_ping
Recreate the symlink properly

sudo ln -s /usr/lib/nagios/plugins/check_ping /usr/local/nagios/libexec/check_ping
Test the plugin manually

/usr/local/nagios/libexec/check_ping -H 127.0.0.1 -w 100.0,20% -c 500.0,60%
Test the plugin manually

/usr/local/nagios/libexec/check_ping -H 192.168.136.130 -w 100.0,20% -c 500.0,60%
You should get something like:

PING OK – Packet loss = 0%, RTA = 0.12 ms
For any doubts and query, please write on YouTube video 📽 comments section.

Note : Flow the Process shown in video 📽.

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Thanks & Regards,

Chitt Ranjan Mahto “Chirag”

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This content originally appeared on DEV Community and was authored by Chitt Ranjan Mahto (Chirag)