Install DSpace 6.x on Ubuntu 16.04 LTS

Installation of prerequisite applications
Open  Applications > Accessories > Terminal and execute the following commands. Apply following commands,

sudo apt update
sudo apt upgrade
sudo apt install leafpad openjdk-8-jdk ant maven

Install PostgreSQL
Apply the following commands one by one to install PostgreSQL 9.6.

sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ xenial-pgdg main" >> /etc/apt/sources.list.d/pgdg.list'
 
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
 
sudo apt-get update

sudo apt install postgresql-9.6

Login to PostgreSQL and create the database

sudo su postgres

createuser --username=postgres --no-superuser --pwprompt dspace

Enter a password for new role: [Enter a password e.g. dspace]

Shall the new role be allowed to create more new roles? (y/n) n

[Enter n and press enter button]

createdb --username=postgres --owner=dspace --encoding=UNICODE -T template0 dspace

psql --username=postgres dspace -c "CREATE EXTENSION pgcrypto;"

exit

Open the following file,

sudo leafpad /etc/postgresql/9.6/main/pg_hba.conf

Add this line to the configuration file at the end:

local all dspace md5

save and close the file

Restart PostgreSQL :

sudo /etc/init.d/postgresql restart

Create a DSpace user
Apply the following commands one by one,

sudo useradd -m dspace
sudo passwd dspace [enter a password for the new user dspace]
sudo mkdir /dspace
sudo chown dspace /dspace

Create a directory to build Dspace

sudo mkdir /build
sudo chmod -R 777 /build
cd /build

Download DSpace into /build directory
Copy-paste following line in the terminal,

wget https://github.com/DSpace/DSpace/releases/download/dspace-6.3/dspace-6.3-src-release.tar.gz

You can find the latest updated of Dspace 6.x version from this page and copy the link to download latest version.

Extracting Dspace package

tar -zxf dspace-6.3-src-release.tar.gz

Open following file and remove a piece of lines.

sudo leafpad /build/dspace-6.3-src-release/dspace-api/pom.xml

Remove the following group of codes. Carefully check the lines in the file.

<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>buildnumber-maven-plugin</artifactId>
<version>1.4</version>
<executions><execution>
<phase>validate</phase>
<goals>
<goal>create</goal>
</goals>
</execution>
</executions>
</plugin>

Save and close the file.

Installation of Dspace
Enter into Dspace package folder and apply following commands one by one.

cd /build/dspace-6.3-src-release
sudo mvn -U package 
cd dspace/target/dspace-installer
sudo ant fresh_install

Installation of Tomcat
Download the and extract the Tomcat package,

cd /opt

sudo wget http://mirrors.estointernet.in/apache/tomcat/tomcat-8/v8.5.50/bin/apache-tomcat-8.5.50.tar.gz


If the above mentioned link not working, visit Tomcat website and download the package.

sudo tar xvzf apache-tomcat-8.5.50.tar.gz

Rename folder "apache-tomcat-8.5.50" to "tomcat"

sudo mv apache-tomcat-8.5.50 tomcat

Delete the Tomcat package file from /opt folder

sudo rm apache-tomcat-8.5.50.tar.gz

Open the following file, 

sudo leafpad /etc/profile

Setup environment variables

Environment variables to find JAVA.

Add following lines at the bottom of the file,

export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64
export CATALINA_HOME=/opt/tomcat

Copy Dspace web apps files to Tomcat folder 

sudo cp -r /dspace/webapps/* /opt/tomcat/webapps

Running Tomcat automatically
You can set up to start the Tomcat server start automatically at the time of system turn on.

Open following file in a Terminal,

sudo leafpad  /etc/init.d/tomcat

Add following lines in the file,

#!/bin/bash
### BEGIN INIT INFO
# Provides:        tomcat8
# Required-Start:  $network
# Required-Stop:   $network
# Default-Start:   2 3 4 5
# Default-Stop:    0 1 6
# Short-Description: Start/Stop Tomcat server
### END INIT INFO

PATH=/sbin:/bin:/usr/sbin:/usr/bin

start() {
 sh /opt/tomcat/bin/startup.sh
}

stop() {
 sh /opt/tomcat/bin/shutdown.sh
}

case $1 in
  start|stop) $1;;
  restart) stop; start;;
  *) echo "Run as $0 <start|stop|restart>"; exit 1;;
esac

save and close the file.

Apply the following commands too;

sudo chmod +x /etc/init.d/tomcat
sudo update-rc.d tomcat defaults

Start Tomcat server,

sudo service tomcat start

Now you can start and stop Tomcat server using the following commands;

sudo service tomcat start
sudo service tomcat stop
sudo service tomcat restart

Make an initial administrator account (an e-person) in DSpace:

Apply following command in a terminal,

sudo /dspace/bin/dspace create-administrator

It will ask to enter the email address for user login.
Enter an email address (e.g. dspace@localhost).
Enter First name and surename (e.g. dspace)
Enter a password.

Delete the build folder

sudo rm -rf /build

Open DSpace in your browser
DSpace has two interfaces; xmlui and jspui. You can load either one Dspace interface in a browser.

http://localhost:8080/xmlui
http://localhost:8080/jspui

Reference:
https://wiki.duraspace.org/display/DSDOC4x/Installing+DSpace

https://www.wissenschaft.com.ng/blog/installing-dspace-6-x-on-ubuntu-14-04-16-04-18-04-lts/