How to install Nagios Server in Ubuntu

After adding the repositories, add Nagios user and group.

root@linuxhelp:~# useradd nagios
root@linuxhelp:~# groupadd nagcmd 

Then add the Nagios and Apache user into Nagios group as follows.

root@linuxhelp:~# usermod -a -G nagcmd nagios
root@linuxhelp:~# usermod -a -G nagios,nagcmd www-data 

Use wget command as shown below to download and extract the Nagios core.

root@linuxhelp:~# wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.2.0.tar.gz 
--2016-10-13 03:57:03--  https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.2.0.tar.gz
Resolving assets.nagios.com (assets.nagios.com)... 72.14.181.71, 2600:3c00::f03c:91ff:fedf:b821
Connecting to assets.nagios.com (assets.nagios.com)|72.14.181.71|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 11155104 (11M) [application/x-gzip]
Saving to: ‘ nagios-4.2.0.tar.gz’ 

nagios-4.2.0.tar.gz                         100%[========================================================================================> ]  10.64M   780KB/s    in 21s     

2016-10-13 03:57:26 (513 KB/s) - ‘ nagios-4.2.0.tar.gz’  saved [11155104/11155104]
root@linuxhelp:~# ls 
Desktop  Documents  Downloads  examples.desktop  Music  nagios-4.2.0.tar.gz  Pictures  Public  Templates  Videos
root@linuxhelp:~# tar -xzvf nagios-4.2.0.tar.gz  
nagios-4.2.0/
nagios-4.2.0/.gitignore
nagios-4.2.0/Changelog
nagios-4.2.0/INSTALLING
nagios-4.2.0/LEGAL
nagios-4.2.0/LICENSE
nagios-4.2.0/Makefile.in
nagios-4.2.0/README
nagios-4.2.0/README.asciidoc
nagios-4.2.0/THANKS
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nagios-4.2.0/xdata/xcddefault.h
nagios-4.2.0/xdata/xodtemplate.c
nagios-4.2.0/xdata/xodtemplate.h
nagios-4.2.0/xdata/xpddefault.c
nagios-4.2.0/xdata/xpddefault.h
nagios-4.2.0/xdata/xrddefault.c
nagios-4.2.0/xdata/xrddefault.h
nagios-4.2.0/xdata/xsddefault.c
nagios-4.2.0/xdata/xsddefault.h

Now compile the Nagios core as shown below.

root@linuxhelp:~# cd nagios-4.2.0/ 
root@linuxhelp:~/nagios-4.2.0# ./configure --with-nagios-group=nagios --with-command-group=nagcmd 
checking for a BSD-compatible install... /usr/bin/install -c
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking whether make sets $(MAKE)... yes
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Web Interface Options:
 ------------------------
                 HTML URL:  http://localhost/nagios/
                  CGI URL:  http://localhost/nagios/cgi-bin/
 Traceroute (used by WAP):  

Review the options above for accuracy.  If they look okay,
type ' make all'  to compile the main program and CGIs.

Then run make script to install Nagios.

root@linuxhelp:~/nagios-4.2.0# make all 
cd ./base & &  make
make[1]: Entering directory ' /home/user1/nagios-4.2.0/base' 
gcc -Wall -I.. -g -O2 -DHAVE_CONFIG_H -DNSCORE -c -o nagios.o nagios.c
nagios.c: In function ‘ main’ :
nagios.c:594:4: warning: ignoring return value of ‘ asprintf’ , declared with attribute warn_unused_result [-Wunused-result]
    asprintf(& mac-> x[MACRO_PROCESSSTARTTIME], " %llu" , (unsigned long long)program_start) 
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before you post a question to one of the mailing lists.
Also make sure to include pertinent information that could
help others help you.  This might include:

     - What version of Nagios you are using
     - What version of the plugins you are using
     - Relevant snippets from your config files
     - Relevant error messages from the Nagios log file

For more information on obtaining support for Nagios, visit:

       https://support.nagios.com

*************************************************************

Enjoy.

root@linuxhelp:~/nagios-4.2.0# make install 
cd ./base & &  make install
make[1]: Entering directory ' /home/user1/nagios-4.2.0/base' 
make install-basic
make[2]: Entering directory ' /home/user1/nagios-4.2.0/base' 
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/bin
/usr/bin/install -c -m 774 -o nagios -g nagios nagios /usr/local/nagios/bin
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  make install-config
     - This installs sample config files in /usr/local/nagios/etc

make[1]: Leaving directory ' /home/user1/nagios-4.2.0' 

root@linuxhelp:~/nagios-4.2.0# make install-commandmode 
/usr/bin/install -c -m 775 -o nagios -g nagcmd -d /usr/local/nagios/var/rw
chmod g+s /usr/local/nagios/var/rw

*** External command directory configured ***

root@linuxhelp:~/nagios-4.2.0# make install-init 
/usr/bin/install -c -m 755 -d -o root -g root /etc/init.d
/usr/bin/install -c -m 755 -o root -g root daemon-init /etc/init.d/nagios

*** Init script installed ***

root@linuxhelp:~/nagios-4.2.0# make install-config 
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/etc
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/etc/objects
/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/nagios.cfg /usr/local/nagios/etc/nagios.cfg
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Remember, these are *SAMPLE* config files.  You' ll need to read
the documentation for more information on how to actually define
services, hosts, etc. to fit your particular needs.
root@linuxhelp:~/nagios-4.2.0# /usr/bin/install -c -m 644 sample-config/httpd.conf /etc/apache2/sites-available/nagios.conf 

Then copy the directory as shown below command.

root@linuxhelp:~/nagios-4.2.0# cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/ 

Change the ownership for the directory.

root@linuxhelp:~/nagios-4.2.0# chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers 

Next we need to download and install Nagios plugins.

root@linuxhelp:~# wget https://nagios-plugins.org/download/nagios-plugins-2.1.2.tar.gz 
--2016-10-13 04:10:58--  https://nagios-plugins.org/download/nagios-plugins-2.1.2.tar.gz
Resolving nagios-plugins.org (nagios-plugins.org)... 72.14.186.43
Connecting to nagios-plugins.org (nagios-plugins.org)|72.14.186.43|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2695301 (2.6M) [application/x-gzip]
Saving to: ‘ nagios-plugins-2.1.2.tar.gz’ 

nagios-plugins-2.1.2.tar.gz                 100%[========================================================================================> ]   2.57M   627KB/s    in 4.4s    

2016-10-13 04:11:04 (593 KB/s) - ‘ nagios-plugins-2.1.2.tar.gz’  saved [2695301/2695301]
root@linuxhelp:~# tar -xzvf nagios-plugins-2.1.2.tar.gz  
nagios-plugins-2.1.2/
nagios-plugins-2.1.2/perlmods/
nagios-plugins-2.1.2/perlmods/Config-Tiny-2.14.tar.gz
nagios-plugins-2.1.2/perlmods/parent-0.226.tar.gz
nagios-plugins-2.1.2/perlmods/Test-Simple-0.98.tar.gz
nagios-plugins-2.1.2/perlmods/Makefile.in
nagios-plugins-2.1.2/perlmods/version-0.9903.tar.gz
nagios-plugins-2.1.2/perlmods/Makefile.am
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nagios-plugins-2.1.2/pkg/solaris/
nagios-plugins-2.1.2/pkg/solaris/preinstall
nagios-plugins-2.1.2/pkg/solaris/solpkg
nagios-plugins-2.1.2/pkg/solaris/pkginfo.in
nagios-plugins-2.1.2/pkg/solaris/pkginfo
nagios-plugins-2.1.2/pkg/redhat/
nagios-plugins-2.1.2/pkg/redhat/requires

To configure Nagios Plugins

Then run the following command to configure Nagios plugin.

root@linuxhelp:~# cd nagios-plugins-2.1.2/ 
root@linuxhelp:~/nagios-plugins-2.1.2# ./configure --with-nagios-user=nagios --with-nagios-group=nagios --with-openssl 
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... no
checking for mawk... mawk
checking whether make sets $(MAKE)... yes
checking whether to disable maintainer-specific portions of Makefiles... yes
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
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.
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--with-gnutls: no
               --enable-extra-opts: yes
                       --with-perl: /usr/bin/perl
             --enable-perl-modules: no
                     --with-cgiurl: /nagios/cgi-bin
               --with-trusted-path: /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
                   --enable-libtap: no

Run the make scripts to install Nagios.

root@linuxhelp:~/nagios-plugins-2.1.2# make 
make  all-recursive
make[1]: Entering directory ' /home/user1/nagios-plugins-2.1.2' 
Making all in gl
make[2]: Entering directory ' /home/user1/nagios-plugins-2.1.2/gl' 
.
.
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make[2]: Leaving directory ' /home/user1/nagios-plugins-2.1.2/po' 
make[2]: Entering directory ' /home/user1/nagios-plugins-2.1.2' 
make[2]: Leaving directory ' /home/user1/nagios-plugins-2.1.2' 
make[1]: Leaving directory ' /home/user1/nagios-plugins-2.1.2' 
root@linuxhelp:~/nagios-plugins-2.1.2# make install 
Making install in gl
make[1]: Entering directory ' /home/user1/nagios-plugins-2.1.2/gl' 
make  install-recursive
make[2]: Entering directory ' /home/user1/nagios-plugins-2.1.2/gl' 
.
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make[2]: Entering directory ' /home/user1/nagios-plugins-2.1.2' 
make[2]: Nothing to be done for ' install-exec-am' .
make[2]: Nothing to be done for ' install-data-am' .
make[2]: Leaving directory ' /home/user1/nagios-plugins-2.1.2' 
make[1]: Leaving directory ' /home/user1/nagios-plugins-2.1.2' 

Now configure Nagios file by uncommenting the following line.

root@linuxhelp:~# vim /usr/local/nagios/etc/nagios.cfg 
cfg_dir=/usr/local/nagios/etc/servers

Now create the directory for servers.

root@linuxhelp:~# mkdir -p /usr/local/nagios/etc/servers 

After creating the directory open the contacts.cfg file and replace the default mail id with yours to receive mail alerts.

root@linuxhelp:~# vim /usr/local/nagios/etc/objects/contacts.cfg 

Next enable the following Apache modules.

root@linuxhelp:~# a2enmod rewrite 
Enabling module rewrite.
To activate the new configuration, you need to run:
  service apache2 restart

root@linuxhelp:~# a2enmod cgi 
AH00557: apache2: apr_sockaddr_info_get() failed for linuxhelp
AH00558: apache2: Could not reliably determine the server' s fully qualified domain name, using 127.0.0.1. Set the ' ServerName'  directive globally to suppress this message
Enabling module cgi.
To activate the new configuration, you need to run:
  service apache2 restart

Then add password for Nagios user “ nagiosadmin” .

root@linuxhelp:~# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin 
New password: 
Re-type new password: 
Adding password for user nagiosadmin

Enable the Nagios virtual host by creating the soft link.

root@linuxhelp:~# ln -s /etc/apache2/sites-available/nagios.conf /etc/apache2/sites-enabled/ 

Create file to start the services for Nagios and add the following services.

root@linuxhelp:~# vim /etc/systemd/system/nagios.service 

[Unit]
Description=Nagios
BindTo=network.target

[Install]
WantedBy=multi-user.target

[Service]
User=nagios
Group=nagios
Type=simple
ExecStart=/usr/local/nagios/bin/nagios /usr/local/nagios/etc/nagios.cfg

Now start the services for Nagios and Apache.

root@linuxhelp:~# systemctl start apache2
root@linuxhelp:~# systemctl start nagios

root@linuxhelp:~# systemctl enable nagios 
Synchronizing state of nagios.service with SysV init with /lib/systemd/systemd-sysv-install...
Executing /lib/systemd/systemd-sysv-install enable nagios

Open and edit the Nagios file and make the following entry into it.

root@linuxhelp:~# vim /etc/init.d/nagios 

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

Now make the Nagios file into an executable format.

root@linuxhelp:~# chmod +x /etc/init.d/nagios 

Once again restart the services.

root@linuxhelp:~# systemctl restart apache2
root@linuxhelp:~# systemctl restart nagios