Monitor Instances with LibreNMS on Ubuntu Bionic

LibreNMS Overview

LibreNMS is a fully featured network monitoring system that supports a wide range of network hardware and operating systems including Linux and Windows. As well as network equipment made by Cisco, Juniper, Foundry, and many more.

The software is based on PHP and MySQL (MariaDB) and is a community-based fork of the last GPL-licensed version of Observium.

Requirements:

Installing LibreNMS

1 . Update the apt repository information:

apt update

2 . Install the required packages:

apt install software-properties-common
add-apt-repository universe
apt update
apt install curl composer fping git graphviz imagemagick mariadb-client mariadb-server mtr-tiny nginx-full nmap php7.2-cli php7.2-curl php7.2-fpm php7.2-gd php7.2-json php7.2-mbstring php7.2-mysql php7.2-snmp php7.2-xml php7.2-zip python-memcache python-mysqldb rrdtool snmp snmpd whois

3 . Create a user for LibreNMS:

useradd librenms -d /opt/librenms -M -r
usermod -a -G librenms www-data

4 . Enter the directory /opt and download LibreNMS:

cd /opt
git clone https://github.com/librenms/librenms.git

5 . Set the permissions:

chown -R librenms:librenms /opt/librenms
chmod 770 /opt/librenms
setfacl -d -m g::rwx /opt/librenms/rrd /opt/librenms/logs /opt/librenms/bootstrap/cache/ /opt/librenms/storage/
setfacl -R -m g::rwx /opt/librenms/rrd /opt/librenms/logs /opt/librenms/bootstrap/cache/ /opt/librenms/storage/

6 . Switch into the librenms user:

su - librenms

7 . Install the PHP dependencies:

./scripts/composer_wrapper.php install --no-dev

8 . Logout from the user session:

exit

Setting up the Database

LibreNMS stores the data collected from the monitored systems in a MySQL database. The open-source fork MariaDB is used in the setup, providing the same features as MySQL.

1 . Run the MariaDB setup assistant to configure a secure root password for the database server:

mysql_secure_installation

2 . Connect to the MariaDB shell with the user root and the password configured in the previous step:

mysql -uroot -p

3 . Create a database and user for LibreNMS and grant permissions to the database:

CREATE DATABASE librenms CHARACTER SET utf8 COLLATE utf8_unicode_ci;
CREATE USER 'librenms'@'localhost' IDENTIFIED BY '<a_secure_password>';
GRANT ALL PRIVILEGES ON librenms.* TO 'librenms'@'localhost';
FLUSH PRIVILEGES;
exit

Replace <a_secure_password> with a secure password of your choice.

4 . Open the file /etc/mysql/mariadb.conf.d/50-server.cnf in a text editor, for example nano:

nano /etc/mysql/mariadb.conf.d/50-server.cnf

Add the following Lines within the [mysqld] section:

innodb_file_per_table=1
lower_case_table_names=0

Save the file by pressing CTRL+O and exit nano by pressing CTRL+X.

5 . Restart the MariaDB server:

systemctl restart mysql

Setting up Nginx

Nginx is an open-source web server and is being used to serve the web frontend of LibreNMS.

1 . Create the file /etc/nginx/sites-available/librenms.example.com by opening it in a text editor:

nano /etc/nginx/sites-available/librenms.example.com

Add the Nginx configuration to the file, save it and exit nano:

server {
 listen      80;
 server_name <librenms.example.com>;
 root        /opt/librenms/html;
 index       index.php;

 charset utf-8;
 gzip on;
 gzip_types text/css application/javascript text/javascript application/x-javascript image/svg+xml text/plain text/xsd text/xsl text/xml image/x-icon;
 location / {
  try_files $uri $uri/ /index.php?$query_string;
 }
 location /api/v0 {
  try_files $uri $uri/ /api_v0.php?$query_string;
 }
 location ~ \.php {
  include fastcgi.conf;
  fastcgi_split_path_info ^(.+\.php)(/.+)$;
  fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
 }
 location ~ /\.ht {
  deny all;
 }
}

Important: Replace <librenms.example.com> with the FQDN of your instance.

2 . Enable the server block by linking it to the sites-enabled directory:

ln -s /etc/nginx/sites-available/librenms.example.com /etc/nginx/sites-enabled/

3 . Restart the Nginx web server:

service nginx restart

4 . Optional: For security reasons, it is recommended to configure HTTPS by following this tutorial.

Setting up SNMP

Simple Network Management Protocol (SNMP) is a protocol for collecting and organizing information about managed devices on IP networks. Data of SNMP is transported using User Datagram Protocol (UDP). Requests are sent to the agent listening on UDP port 161.

1 . Copy the SNMP configuration file in the directory /etc/snmp:

cp /opt/librenms/snmpd.conf.example /etc/snmp/snmpd.conf

2 . Open the configuration file in a text editor:

nano /etc/snmp/snmpd.conf

Edit the string RANDOMSTRINGGOESHERE to a SNMP group name of your choice.

Save the file and exit nano.

3 . To display distribution information, download the distro script and make it executable:

curl -o /usr/bin/distro https://raw.githubusercontent.com/librenms/librenms-agent/master/snmp/distro
chmod +x /usr/bin/distro

4 . Restart the SNMP service:

systemctl restart snmpd

Setting up the Cronjob and Logrotate

Cron is a job scheduler available on Linux systems. It can be used to run jobs (i.e. shell scripts) automatically at given points in time to automatize system maintenance. Logrotate is a tool to rotate log files automatically. This means to clean up log files periodically by removing old contents to ensure the disk space they occupy does not exceed a configured maximum value.

1 . Copy the cron configuration file into the directory /etc/cron.d/ to execute actions automatically:

cp /opt/librenms/librenms.nonroot.cron /etc/cron.d/librenms

The file contains the basic cronjobs required by LibreNMS.

2 . To avoid that the log files of LibreNMS become too large, logrotate can rotate them out from time to time to save space. Enable it by copying the provided configuration file into /etc/logrotate.d:

cp /opt/librenms/misc/librenms.logrotate /etc/logrotate.d/librenms

Running the Web Installer

1 . Open a web browser and go to your LibreNMS instance:

https://librenms.example.com/install.php

LibreNMS installation

2 . Fill in the database connection parameters and the password set during database creation:

LibreNMS installation

3 . Configure a user and password for LibreNMS and complete the setup.

4 . Login to LibreNMS with the user and password created in the previous step:

LibreNMS installation

Adding Localhost

Start by adding the local host as the first device to monitor:

1 . Once logged in, click on Devices, then Add Device in the pop-up menu:

LibreNMS Add Device

2 . Enter the hostname localhost, keep SNMP on, leave the values for SNMP version and Port Association Mode as preset. Enter the configured community name in the file /etc/snmp/snmpd.conf as value for Community. Once all values are set, click on Add Device to add the device:

LibreNMS Add Device

3 . LibreNMS starts polling the device and different graphs are created, showing the status of the device.

Adding a Remote Device

LibreNMS is capable of monitoring many different network devices. To monitor a remote cloud instance or bare metal server, the use of SNMP is widespread. SNMP stands for Simple Network Management Protocol. It is a protocol that was designed for monitoring and management purposes of network-connected devices (servers, switches, printers, routers, etc.). On Ubuntu systems a daemon called SNMPd is available to listen and reply to SNMP requests.

1 . To monitor another cloud instance or bare metal server, connect to the machine as root:

ssh root@second_cloud_instance

2 . Update the apt repository inventory:

apt update

3 . To display distribution information, download the distro script and make it executable:

curl -o /usr/bin/distro https://raw.githubusercontent.com/librenms/librenms-agent/master/snmp/distro
chmod +x /usr/bin/distro

4 . Install SNMPd via apt:

apt install snmpd

5 . Open the SNMPd configuration file in a text editor (e.g. nano):

nano /etc/snmp/snmpd.conf

6 . Delete the content present in the default configuration file and replace it with the example below:


# Change RANDOMSTRINGGOESHERE to your preferred SNMP community string
com2sec readonly  123.123.123.123         RANDOMSTRINGGOESHERE
group MyROGroup v2c        readonly
view all    included  .1                               80
access MyROGroup ""      any       noauth    exact  all    none   none

syslocation "Paris, France"
syscontact Your Name <your@email.address>

#Distro Detection
extend .1.3.6.1.4.1.2021.7890.1 distro /usr/bin/distro

Edit the file to meet your requirements, the meaning of the different lines is explained below:

  • com2sec readonly 123.123.123.123 RANDOMSTRINGGOESHERE - This line maps a security string to a community name. A security string is an access policy, an IP address limitation (replace 123.123.123.123 with the IP address of the LibreNMS instance) and a community name (replace RANDOMSTRINGGOESHERE with the community name configured during the installation of LibreNMS).

  • The line group MyROGroup v2c readonly maps a group (MyROGroup) to a security name (v2c readonly).

  • The line view defines a subset of which information from the MIB is visible when polling the device via SNMP

  • With the line access MyROGroup "" any noauth exact all none none acces rules are tied to the group set before. In this example it means that the group MyROGroup can, in any context (“”), access the data over any version of the protocol (any), without authentication (noauth), matching the exact context (exact), allowing access to all view rules (all). No write (none) or modify access (none) is permitted.

  • syslocation “Paris, France” is pretty self-explanatory and specifies the geographical location of the machine.

  • syscontact Your Name <your@email.address> defines the administrative contact for the machine.

  • The last line is used to communicate the distribution information collected by distro via SNMP

Edit the values in the file towards your needs before saving it and exiting the editor.

7 . Restart the SNMP service:

systemctl restart snmpd

8 . Add the device to LibreNMS by clicking on Devices, then Add Device in the pop-up menu from within the LibreNMS web interface.

9 . Enter the hostname of the device, keep SNMP on, leave the values for SNMP version and Port Association Mode as preset. Enter the community name set in the file /etc/snmp/snmpd.conf as value for Community. Once all values are set, click on Add Device to add the device.

10 . LibreNMS starts polling the device and creating different graphs showing the status of the device:

LibreNMS Graphs

For more information about the configuration options of SNMP, refer to the official documentation. You may also refer to the documentation of LibreNMS.

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