Open a terminal and apply following commands,

sudo su

wget -O- http://debian.koha-community.org/koha/gpg.asc | sudo apt-key add -

echo deb http://debian.koha-community.org/koha squeeze main | sudo tee /etc/apt/sources.list.d/koha.list

sudo apt-get update
sudo apt-get upgrade

sudo apt-get install koha-common


Initial Configuration
Create a new file

leafpad /etc/koha/koha-sites.conf

Add the following lines and save.

DOMAIN=".yourdomain.org"  # Change this to be your domain. Any instance will be a subdomain of this string.
INTRAPORT="8000"  # TCP listening port for the administration interface
INTRAPREFIX=""  # For administration interface URL: Prefix to be added to the instance name.
INTRASUFFIX="-intra"  # For administration interface URL: Suffix to be added to the instance name.
DEFAULTSQL=""  # a value is generally not needed.
OPACPORT="8001"  # TCP listening port for the users' interface (if you skip this, the apache default of 80 will be used)
OPACPREFIX=""  # For users' interface URL: Prefix to be added to the instance name.
OPACSUFFIX=""  # For users' interface URL: Suffix to be added to the instance name.
ZEBRA_MARC_FORMAT="marc21"  # Specifies format of MARC records to be indexed by Zebra. Possible values are 'marc21', 'normarc' and 'unimarc'
ZEBRA_LANGUAGE="en"  # Primary language for Zebra indexing. Possible values are 'en', 'fr' and 'nb'

Adding ports
Open following file and add ports

leafpad /etc/apache2/ports.conf

Add two ports for Koha

Listen 8000
Listen 8001
 

Apply following commands,  

sudo a2enmod rewrite

Instance creation

sudo apt-get install mysql-server

sudo apt-get clean

sudo koha-create --create-db library

Ubuntu MySQL security Tweak

sudo su

mysql -u root -p

USE mysql;

SELECT host,user FROM user;

DELETE FROM user WHERE user=''; SELECT host,user FROM user;

FLUSH PRIVILEGES;

QUIT

Configuring Apache

sudo a2dissite 000-default

sudo a2enmod rewrite
sudo a2enmod deflate
sudo a2ensite library
sudo /etc/init.d/apache2 restart

Start web installation of Koha

The username to log in with will be koha_library and the password will be near the end of /etc/koha/sites/library/koha-conf.xml

Apply the following command to see the koha login password,

sudo xmlstarlet sel -t -v 'yazgfs/config/pass' /etc/koha/sites/library/koha-conf.xml

Open following link,

http://127.0.1.1:8000  

Zebra rebuild command

sudo su

koha-rebuild-zebra -v -f koha_library

Reference

Koha on Ubuntu packages