Upgrading Magento is quite the undertaking. Finding a clear set of steps to follow, let alone actually performing the upgrade, can be a substantial challenge, so we’ve put together a detailed guide for upgrading from Magento Community Edition 1.4.2.0 to 1.5.1.0. It is tempting to try and upgrade directly from 1.4.2.0 to the latest stable edition (currently 1.7.0.2); however, this is not recommended as it will likely break your store. Follow the steps below to upgrade to 1.5.1 and then proceed with further upgrades.

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Steps to Upgrade Magento 1.4.2.0 to 1.5.1.0
The preferred method of upgrading Magento 1.4.2 to 1.5.1 is to run a fresh install of 1.5.1 and connect it to a copy of the 1.4.2 database that you want to upgrade at the appropriate step in the installation. Do not use your live database for this! Make a backup per the below instructions.

1) Before doing anything, create a full backup of your site. Always backup!

2) Create a backup of your database by running the mysqldump command from SSH. If you don’t have SSH access, you can export a copy of your database via the Magento admin panel (System > Tools > Backup, more) or phpMyAdmin. Make sure you select the correct database and the appropriate export options if using phpMyAdmin. A benefit of the first two methods is that you don’t need to worry about export options.

If using SSH:

mysqldump -uusername -ppassword database_name > database_copy.sql

3) Create a new database in cPanel and import the database_copy.sql file you just created in Step 2. Note that the direction of the angle bracket (pointy arrow in layman’s terms) changes directions and be sure that you use the new database name (you don’t want to import the exported data back into your live database). You can also import database_copy.sql with phpMyAdmin if you don’t have SSH access.

mysql -uusername -ppassword new_database < database_copy.sql

4) Create a development subdomain or directory and get a copy of the 1.5.1.0 fileset to install. If you don’t have SSH access, you can download from the Magento website, unzip, and upload via FTP. Whether you use SSH or FTP for this step, make sure that you upload / unzip the folders to the development directory. You do not want to overwrite any of the files on your live site!

wget http://www.magentocommerce.com/downloads/assets/1.7.0.2/magento-1.5.1.0.tar.gz
tar -zxvf magento-1.5.1.0.tar.gz
mv magento/* magento/.htaccess .
chmod -R o+w media var
chmod o+w app/etc

Line 1 gets the fileset via wget. Line 2 unzips it (it unzips in to a /magento/ subdirectory). Line 3 moves all files from the /magento/ sub-directory into the parent directory. Lines 4 and 5 update permissions.

Once all the files for 1.5.1 are uploaded / unzipped, proceed to Step 5.

5) Run the Magento installer by visiting yourdomain.com/yourdevelopmentdirectory/. Agree to the license and configure localization settings. For the Database Connection section, enter the database and user info for the new database that you created in Step 3. Remember to check to see if your database is using prefixes. If so, be sure to fill in that field as well. Once you have submitted your database info, the Magento installer will automatically update your database from 1.4.2 to 1.5.1. If the update is successful, you will be prompted to enter new admin credentials and then shown an installation success screen.

6) Clear /var/cache/ and /var/session/ by deleting all files and folders in each directory.

7) Load your upgraded store and check for any errors. To confirm that you have upgraded to 1.5.1.0, log into the admin panel and check the footer. If it reads “Magento ver. 1.5.1.0”, then give yourself a pat on the back. You have successfully upgraded to 1.5.1!

If you experience any errors during the upgrade process, please contact us. We also offer Magento upgrade services.