How to upgrade Magento 1.6 to magento 1.9

Question

I am having my current website running on Magento 1.6. I am looking to upgrade it to 1.9 but don't know how to start. I went through the below articles but was not able to move ahead.

http://www.customerparadigm.com/magento-development/upgrade/how-to-upgrade-magento/

http://www.crucialwebhost.com/kb/installing-magento-via-ssh/

Can anyone please help me from ground level. I need to know it from scratch. I wanted to replace the below code but was not able to locate the file in my database. I am currently using filezilla to access my server file. My database is maintained by a different company called nexcess.

wget http://www.magentocommerce.com/index.php/getmagento/1.9.1.0/magento-1.9.1.0.tar.gz
wget http://www.magentocommerce.com/downloads/assets/1.9.0.0/magento-sample-data-1.9.0.0.tar.gz
tar xvf magento-1.9.1.0.tar.gz
tar xvf magento-sample-data-1.9.0.0.tar.gz
mv magento-sample-data-1.9.0.0/media/* magento/media/
mv magento-sample-data-1.9.0.0/magento_sample_data_for_1.9.0.0.sql magento/data.sql
mv magento/* magento/.htaccess .
mysql -h DBHOST -u DBUSER -pDBPASS DBNAME < data.sql
rm -rf *.sample magento/ magento-sample-data-1.9.0.0/
rm -rf magento-1.9.1.0.tar.gz magento-sample-data-1.9.0.0.tar.gz data.sql

Please help me how to go through with it

Answer 1

Upgrade Roadmap for CE 1.9.0.1 from 1.6

1) take a backup of current database and current 1.6 code.
2) download latest magento from the http://www.magentocommerce.com/download
3) remove all folders and files from your 1.6 code (but you should have backup somewhere) and place all folders and files from the 1.9.
4) now from your 1.6 merge your following folders into the 1.9
    - Community app/code/community
    - Local app/code/local
    - Media 
    - your theme or package (app/design/frontend/default/<ur theme> or app/design/frontend/<your package>)
    - custom folders from Skin (both for adminhtml and frontend).
    - copy your custom xml files from app/etc/modules/ to current app/etc/modules/
    - any custom admin theme folder from adminhtml/default/yourtheme.
    - copy your custom folders from adminhtml/default/default/ (1.6) to adminhtml/default/default/ (1.9).
    - custom js files if any from app/js/.
5) now go to app/etc/local.xml.Edit database details their.put your database username and password and database name.
6) now check the site.it done.`enter code here`

P.S. for more information check my answer on http://magento-online-tutorials.blogspot.in/2015/06/magento-upgrade-from-17-to-19.html

Answer 2

Any template you are using will need to be upgraded to use formkeys, otherwise your add to cart, registration, etc. will fail mightily.

Time to fire up a dev or staging server so you don't break your source of income.