There are coexistence for 2 version of Gallery. Gallery 1.x and Gallery 2.x One question you may ask is why 2 versions. For more information on the 2 version comparison, do take a look G1-G2 Comparison from Gallery
This blog entry will focus on the Gallery 1.5 which uses File Metadata Storage. This documentation is a modification of the original documentation Gallery1:Installation on a Unix/Linux Server with Shell Access
Step 1: Change your current working directory to the directory where you want to install Gallery, and download the Gallery tarball
cd /var/html/www
Step 2: Change to your fresh gallery directory
cd gallery
Step 3: Create two blank files, .htaccess and config.php, and chmod them 0666
touch .htaccess
touch config.php
chmod 0666 .htaccess config.php
Step 4: Assuming you are saving the album in the home directory of user named "photo" /home/photo
cd /home/photo/public_html
mkdir albums
chmod 0777 albums
cd /home
chmod 711 /home/photo
Create a softlink from /var/www/html/albums to /home/photo/public_html/albums
cd /var/www/html/
ln -s /home/photo/public_html/albums albums
Step 5: Configure Apache
vim /etc/httpd/conf/httpd.confType the following in httpd.conf
Restart Apache
Service httpd restart
Step 6: Install the latest version of jhead
You have to enable your EPEL repository to get the latest jhead 2.87
yum install jhead
Step 7: Launch the Gallery web-based configuration......
http://yourwebsite/gallery/setup and follow through...
Your Gallery should be up and running in no-time