Have you logged into WordPress and you get the message “WordPress update available, click here to upgrade”, you click “here”, wait and then the upgrade fails?
This is a common problem so we would like to post the solution for our clients:
1) Ensure that your FTP user is the owner of your WordPress install directory, this is most likely not the problem unless you have your own dedicated server and installed WordPress using root user.
2) Ensure that your WordPress directory has the correct permissions, it should be 755. This is the most probable problem. Change the permissions to 755 and then try the WordPress upgrade again.
If your FTP user is not the owner of your WordPress directory OR your WordPress directory has permissions other than 755, your WordPress install/upgrade will fail with the message “Could not copy file: /var/www/wordpress/wp-activate.php”.