In this post we will Install Nagios on Ubuntu 18.04. Nagios is a solid network monitoring tool that has a bit of a learning curve.
We are going to install Nagios Core 4.4.2 which is the latest open source version of Nagios as of this writing.
We will start off with a fresh install of Ubuntu Server 18.04 and perform all the updates. Next we will reboot.
sudo apt update && apt upgrade -y
Next, do a reboot in case we got a new kernel.
reboot
We are now ready to install Nagios.
Installing Nagios Server
First lets download Nagios
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.2.tar.gz
We also need to download Nagios plugins.
wget https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
Next we need to untar both tarballs.
tar -xzvf nagios-4.4.2.tar.gz tar -xzvf nagios-plugins-2.2.1.tar.gz
We are going to install Nagios Core from source which means are going to have to build it.
But first we need to install some dependencies.
sudo apt-get install wget build-essential apache2 php php-gd libgd-dev unzip sendmail
Create Nagios User
We are going to create a nagios user and a user group called nagcmd.
We will then add the nagios user to the nagcmd user group.
finally we will add both the nagios user and the nagcmd user group to the www-data group.
Run the following commands:
useradd nagios groupadd nagcmd usermod -aG nagcmd nagios usermod -aG nagios,nagcmd www-data
Building Nagios
Now it is time to build Nagios from source.
Change to the nagios-4.4.2 directory.
cd nagios-4.4.2/
Next run the configuration script.
./configure --with-command-group=nagcmd --with-mail=/usr/bin/sendmail --with-httpd-conf=/etc/apache2/
This tells the nagios build scripts to set the command group to the nagcmd user group, send emails using sendmail, and tells it where to put our web site configuration.
Now lets compile everything. Run the following commands.
make all
Now we need to use make to install everything.
make install make install-init make install-config make install-commandmode make install-webconf
Awesome we now have Nagios Core installed. But we have no configuration at this point.
Configuring Nagios Core
The tarball we downloaded earlier comes with some sample configuration files.
Let’s copy those over.
cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/ chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers
Now lets verify that our config is good to go.
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
You should see something like this:
Nagios Core 4.4.2 Copyright (c) 2009-present Nagios Core Development Team and Community Contributors Copyright (c) 1999-2009 Ethan Galstad Last Modified: 2018-08-16 License: GPL Website: https://www.nagios.org Reading configuration data... Read main config file okay... Read object config files okay... Running pre-flight check on configuration data... Checking objects... Checked 8 services. Checked 1 hosts. Checked 1 host groups. Checked 0 service groups. Checked 1 contacts. Checked 1 contact groups. Checked 24 commands. Checked 5 time periods. Checked 0 host escalations. Checked 0 service escalations. Checking for circular paths... Checked 1 hosts Checked 0 service dependencies Checked 0 host dependencies Checked 5 timeperiods Checking global event handlers... Checking obsessive compulsive processor commands... Checking misc settings... Total Warnings: 0 Total Errors: 0 Things look okay - No serious problems were detected during the pre-flight check
Everything looks good.
So now we can enable our nagios site. Run the following commands:
cp /etc/apache2/nagios.conf /etc/apache2/sites-available/nagios.conf a2ensite nagios a2enmod rewrite cgi
Restart Apache to enable the rewrite module and our new site.
systemctl restart apache2
Now let’s configure SystemD.
Edit a new file /etc/init.d/nagios and add the following contents:
#! /bin/sh ### BEGIN INIT INFO # Provides: skeleton # Required-Start: $remote_fs $syslog # Required-Stop: $remote_fs $syslog # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: Example initscript # Description: This file should be used to construct scripts to be # placed in /etc/init.d. ### END INIT INFO # Author: Foo Bar# # Please remove the "Author" lines above and replace them # with your own name if you copy and modify this script. # Do NOT "set -e" # PATH should only include /usr/* if it runs after the mountnfs.sh script PATH=/sbin:/usr/sbin:/bin:/usr/bin DESC="Nagios" NAME=nagios DAEMON=/usr/local/nagios/bin/$NAME DAEMON_ARGS="-d /usr/local/nagios/etc/nagios.cfg" PIDFILE=/usr/local/nagios/var/$NAME.lock SCRIPTNAME=/etc/init.d/$NAME # Exit if the package is not installed [ -x "$DAEMON" ] || exit 0 # Read configuration variable file if it is present [ -r /etc/default/$NAME ] && . /etc/default/$NAME # Load the VERBOSE setting and other rcS variables . /lib/init/vars.sh # Define LSB log_* functions. # Depend on lsb-base (>= 3.2-14) to ensure that this file is present # and status_of_proc is working. . /lib/lsb/init-functions # # Function that starts the daemon/service # do_start() { # Return # 0 if daemon has been started # 1 if daemon was already running # 2 if daemon could not be started start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON --test > /dev/null \ || return 1 start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON -- \ $DAEMON_ARGS \ || return 2 # Add code here, if necessary, that waits for the process to be ready # to handle requests from services started subsequently which depend # on this one. As a last resort, sleep for some time. } # # Function that stops the daemon/service # do_stop() { # Return # 0 if daemon has been stopped # 1 if daemon was already stopped # 2 if daemon could not be stopped # other if a failure occurred start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE --name $NAME RETVAL="$?" [ "$RETVAL" = 2 ] && return 2 # Wait for children to finish too if this is a daemon that forks # and if the daemon is only ever run from this initscript. # If the above conditions are not satisfied then add some other code # that waits for the process to drop all resources that could be # needed by services started subsequently. A last resort is to # sleep for some time. start-stop-daemon --stop --quiet --oknodo --retry=0/30/KILL/5 --exec $DAEMON [ "$?" = 2 ] && return 2 # Many daemons don't delete their pidfiles when they exit. rm -f $PIDFILE return "$RETVAL" } # # Function that sends a SIGHUP to the daemon/service # do_reload() { # # If the daemon can reload its configuration without # restarting (for example, when it is sent a SIGHUP), # then implement that here. # start-stop-daemon --stop --signal 1 --quiet --pidfile $PIDFILE --name $NAME return 0 } case "$1" in start) [ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME" do_start case "$?" in 0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;; 2) [ "$VERBOSE" != no ] && log_end_msg 1 ;; esac ;; stop) [ "$VERBOSE" != no ] && log_daemon_msg "Stopping $DESC" "$NAME" do_stop case "$?" in 0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;; 2) [ "$VERBOSE" != no ] && log_end_msg 1 ;; esac ;; status) status_of_proc "$DAEMON" "$NAME" && exit 0 || exit $? ;; #reload|force-reload) # # If do_reload() is not implemented then leave this commented out # and leave 'force-reload' as an alias for 'restart'. # #log_daemon_msg "Reloading $DESC" "$NAME" #do_reload #log_end_msg $? #;; restart|force-reload) # # If the "reload" option is implemented then remove the # 'force-reload' alias # log_daemon_msg "Restarting $DESC" "$NAME" do_stop case "$?" in 0|1) do_start case "$?" in 0) log_end_msg 0 ;; 1) log_end_msg 1 ;; # Old process is still running *) log_end_msg 1 ;; # Failed to start esac ;; *) # Failed to stop log_end_msg 1 ;; esac ;; *) #echo "Usage: $SCRIPTNAME {start|stop|restart|reload|force-reload}" >&2 echo "Usage: $SCRIPTNAME {start|stop|status|restart|force-reload}" >&2 exit 3 ;; esac :
Save the file and restart everything.
systemctl restart apache2 systemctl start nagios systemctl enable nagios
Create an Admin user for the web interface.
We need to create an administrator user for when we access the Nagios web interface.
Run the following command to create a nagiosadmin account.
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
Enter the password you want to use.
Now we need to build and install the Nagios Plugins that we downloaded earlier.
Install Nagios Plugins
First we need to change to the plugins directory we created.
cd ../nagios-plugins-2.2.1/
Run the configuration script.
./configure --with-nagios-user=nagios --with-nagios-group=nagios
Build and install the plugins.
make make install
We now have everything installed and we can view our Nagios web application.
Browse to the following URL.
http://{your_server}/nagios
You will see the Nagios web interface.
Conclusion
In this post, we installed Nagios Core and some sample plugins. In a later post, I will walk you through how to configure a Nagios agent so that we can monitor everything.
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