Upgrading Drupal

The following download is provided for those users who do not want to overwrite all of the files in their Drupal 6.14 installation. Using a file comparison utility, the following zip file contains only the date modified files for the latest release of Drupal 6.15.

Upload the new files to your Drupal site, then log into your site as the administrator and run update.php. A link to the update.php file can be found on the Administer » Site building » Modules page.

Hi All..
I have a question. I am developing my website in Drupal. I have used several core and contributed modules. Some of the contributed modules i have costomized.. what i want to know is if there is an update for that particular module is available and if i want to upgrade that module.. all my customize settings for that module will be lost? or is there any way using which i can upgrade my module as well as my customize settings for that particular module remains intact?
Plese reply soon..its quite urgent

Just upgraded from 6.14 to 6.15, all modules disabled, update was succesful, but now when I try edit any existing content I get this error:

warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'magazine_article_node_form' was given in /home/content/g/a/a/gaaorg/html/2010/drupal/includes/form.inc on line 372.

Thanks in advance.

Ok, so a new security update just came out. What is the easiest,least painful way of updating?

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nevermind, it was easy. just copy and paste the contents of drupal-6.15 folder into your current folder containing your files and "overright all files" should be selected. So far, haven't noticed any problems.

Sorry to bother any of you fine peeps.

After upgrading to 6.15, my admin page indicated "You do not have any administrative items", and the page was empty of any admin options. (The path is /admin.) I believe it is related to the Administrative Menu module because the page returned after I disabled the module.

I've copied my modules / scripts and other files over to my old 6.14 installation...
And ran mysite/update.php

But it keeps bugging me of not being 6.15, but 6.14.

What is wrong?