Install Ubuntu Server as usual
Don't forget to install Openssh Server during the process

After it finished, if you want to install lightweight desktop: (this is optional, because most of the works are done in terminal via ssh)
For ex: (lxde)

#sudo apt-get install --no-install-recommends lubuntu-desktop

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Now to install NetXMS (current: 2.0.6)

#apt-get update
#apt-get install mysql-server
#apt-get install tomcat7
#apt-get install libmysqlclient-dev
#apt-get install libssl-dev
#apt-get install g++
#apt-get install c++

Create a database:

#sudo mysql -u root
mysql> CREATE DATABASE netxms;
mysql> GRANT ALL ON netxms.* TO netxms@localhost IDENTIFIED BY 'password';
mysql> quit

Download the NetXMS server package:

#wget http://www.netxms.org/download/netxms-2.0.6.tar.gz
#tar -xvf  netxms-2.0.6.tar.gz

Configure the package:

#cd netxms.x.x.x
#sudo sh ./configure --with-server --with-mysql --with-agent (it will show some results)
#sudo make
#sudo make install
#sudo cp contrib/netxmsd.conf-dist /etc/netxmsd.conf
#sudo cp contrib/nxagentd.conf-dist /etc/nxagentd.conf
#sudo nano /etc/netxmsd.conf

sample output:

DBDriver = mysql.ddr
DBServer = localhost
DBName = netxms
DBLogin = netxms
DBPassword = password
LogFile = /var/log/netxmsd
LogFailedSQLQueries = yes

#sudo nano /etc/nxagentd.conf
MasterServers = 127.0.0.1, 192.168.1.1

Initiaze agent and server services:

#sudo cat /etc/ld.so.conf.d/libc.conf (check it contain /usr/local/lib, if not add it)
#sudo ldconfig
#sudo ldconfig -p|grep libnetxms (it shows some output)
#/usr/local/bin/nxdbmgr init /usr/local/share/netxms/sql/dbinit_mysql.sql
#/usr/local/bin/nxagentd -d
#/usr/local/bin/netxmsd -d

Download the web based management:

#wget http://www.netxms.org/download/webui/nxmc-2.0.6.war
#sudo rename nxmc-2.0.6.war nxmc.war
#sudo cp nxmc.war /var/lib/tomcat7/webapps/

#sudo netxmsd  (this is to start netXMS server properly, otherwise you will get connection refused when you login)

Open browser:
http://ip_address:8080/nxmc/nxmc
(default username: admin, password: netxms)

NetXMS website: http://www.netxms.org/
My installation was based on this reference, though there was some hiccups along the way!