When setting up SMART monitoring via Nagios on Ubuntu servers, I've found these plugins to be the most reliable and feature-rich:

# Example command to check all drives using check_smart.pl:
/usr/lib/nagios/plugins/check_smart.pl -d /dev/sda -i

Here's my working configuration that monitors both attributes and scheduled tests:

# /etc/nagios-plugins/config/smart.cfg
define command {
    command_name    check_smart
    command_line    /usr/lib/nagios/plugins/check_smart.pl -d $ARG1$ -i -w $ARG2$ -c $ARG3$
}

# /etc/nagios3/conf.d/host-smart.cfg
define service {
    use                     generic-service
    host_name               storage-server
    service_description     SMART Health /dev/sda
    check_command           check_smart!/dev/sda!5,10!10,20
    notification_options    w,c,r
}

The best plugins allow setting custom thresholds for specific attributes:

# Monitoring reallocated sector count with custom thresholds
define service {
    host_name               storage-server
    service_description     SMART Reallocated Sectors /dev/sdb
    check_command           check_smart!/dev/sdb!5:5,10:10!10:10,20:20
}

Before using any SMART monitoring plugins, ensure these packages are installed:

sudo apt-get install smartmontools libmonitoring-plugin-perl \
nagios-plugins-basic nagios-plugins-extra

If you encounter permission problems when running checks, add the nagios user to the disk group:

sudo usermod -a -G disk nagios
sudo systemctl restart nagios

For more detailed monitoring, consider combining multiple plugins to cover all aspects of disk health monitoring.

When integrating SMARTd/smartmontools with Nagios on Ubuntu servers, four primary plugin options emerge from Monitoring Exchange:

1. check_smart.pl (Perl-based)
2. check_smartmon (Python implementation) 
3. check_smart_attributes (Bash script)
4. check_ide_smart (C-based solution)

For Ubuntu environments, check_ide_smart offers the most robust solution with direct hardware access and NRPE compatibility. Installation requires:

wget http://www.monitoringexchange.org/p/download/check_ide_smart.tar.gz
tar xvf check_ide_smart.tar.gz
cd check_ide_smart/
./configure
make
sudo make install

Sample NRPE configuration for /etc/nagios/nrpe.cfg:

command[check_smart]=/usr/local/nagios/libexec/check_ide_smart -d /dev/sda -i
command[check_smart_threshold]=/usr/local/nagios/libexec/check_ide_smart -d /dev/sda -a -w 5 -c 10

For comprehensive monitoring across multiple drives:

#!/bin/bash
for drive in /dev/sd[a-z]; do
  /usr/local/nagios/libexec/check_ide_smart -d $drive -a -w 5 -c 10
done

For environments requiring Python:

sudo apt install python3-smartmontools
wget https://raw.githubusercontent.com/prometheus-community/node-exporter-textfile-collector-scripts/master/smartmon.sh
chmod +x smartmon.sh