Upgrade to WordPress 2.0

WordPress 2.0 has a LOT of new code. Be very sure that you really do want to upgrade.

It is very important that you backup your database before upgrading. This is an essential step and is your only insurance should something go wrong. It is also your only way of going back to your current version if you do not like the new one.

BACKUP EVERYTHING

I have a guide to backing up your database which you should follow. If you are unsure about phpmyadmin or you do not have such access, please install and use Skippy's backup plugin

If you have hacked any files at all (don't forget your quicktags), download those files or the whole blog.

You must also backup your .htaccess file. Copy this to your computer and keep it safe.

There are some Q & A at the bottom of the page which you may wish to read before starting.

If you have a Multi-user blog, please do read everything about the new roles system and understand the impact of the changes on your existing user management before you upgrade.

Thanks due to Macmanx for assisting, and to Michael for the Dutch translation.

There have been a huge amount of changes 'under the hood' with this version. Because of this, you really should do a complete upgrade as detailed below. If you are after a changelog so you can decide what files to upload, you will not find it here.

DO NOT delete: wp-config.php or the wp-includes/languages folder (if used) or the /wp-content folder but you MUST delete the /wp-content/cache folder. It could cause problems if the cache is not deleted.

This version of WordPress is slightly different to previous versions - the wp-images directory is not part of the download. If you use this directory at all, then do NOT delete that directory from the server. Leaving that directory there is not a problem.

The Short Version

Delete /wp-admin, /wp-includes, /wp-content/cache and all the wp-* files at root
Rename your .htaccess file to htaccess.txt (just to be sure of keeping it)
Upload the new files.
Upload the new plugins in wp-content/plugins
Run /wp-admin/upgrade.php

The Longer Version
You are advised to deactivate any plugins while you upgrade.
This can take quite a while and you might not want to bother .... If there is a conflict though, you will get an error of some degree.
Your choice.....

Step One:
You need to delete the old WordPress files from the server.
You may think it is quicker to just overwrite old files, but this is the cause of many many problems - if you post to the forums with an upgrade problem it's about the first thing we will ask - so please do not do this.

If you have not made any changes to the core files inside wp-admin or wp-includes, you can just delete both those folders. If you are at all unsure, here is the list of files in those directories that you must delete.
Rename your .htaccess file to htaccess.txt

root
readme.html
index.php
wp.php
wp-atom.php
wp-blog-header.php
wp-comments-post.php
wp-commentsrss2.php
wp-feed.php
wp-links-opml.php
wp-login.php
wp-mail.php
wp-pass.php
wp-rdf.php
wp-register.php
wp-rss.php
wp-rss2.php
wp-settings.php
wp-trackback.php
xmlrpc.php
license.txt
wp-admin
wp-admin.css
quicktags.js
admin.php
admin-footer.php
admin-functions.php
admin-header.php
bookmarklet.php
categories.php
edit.php
edit-comments.php
edit-form.php
edit-form-advanced.php
edit-form-comment.php
edit-page-form.php
edit-pages.php
import-b2.php
import-blogger.php
import-greymatter.php
import-livejournal.php
import-mt.php
import-rss.php
import-textpattern.php
index.php
install.php
install-helper.php
link-add.php
link-categories.php
link-import.php
link-manager.php
link-parse-opml.php
menu.php
menu-header.php
moderation.php
options.php
options-discussion.php
options-general.php
options-head.php
options-misc.php
options-permalink.php
options-reading.php
options-writing.php
page-new.php
plugin-editor.php
plugins.php
post.php
profile.php
setup-config.php
sidebar.php
templates.php
theme-editor.php
themes.php
update-links.php
upgrade.php
upgrade-functions.php
upgrade-schema.php
upload.php
user-edit.php
users.php
wp-includes
classes.php
class-IXR.php
class-pop3.php
class-snoopy.php
comment-functions.php
default-filters.php
feed-functions.php
functions.php
functions-compat.php
functions-formatting.php
functions-post.php
gettext.php
kses.php
links.php
locale.php
pluggable-functions.php
rss-functions.php
streams.php
template-functions-author.php
template-functions-category.php
template-functions-general.php
template-functions-links.php
template-functions-post.php
vars.php
version.php
wp-db.php
wp-l10n.php

Step Two:
Upload wp-admin and all the files inside it.
Upload wp-includes and all the files inside it.
Open the wp-content folder. Be sure to upload the new plugins that are inside the /wp-content folder.
The Default and the Classic themes have changed slightly but you do not need to bother with them if you already have a theme you like. You do not have to upload them.
However, if you are using either Default or Classic AND you have not changed them at all then you should indeed upload the new themes and use them. (There is a funky colour editor in the Default theme which you might want to check out).

IMPORTANT
If you want to use the built-in database backup plugin, you must make your wp-content directory writable. You should use the MINIMUM permissions necessary for this to happen.
If you do NOT want to use that plugin, do NOT change the permissions you already have.
If you are unsure about security, either ASK or do NOT use that plugin.
NEVER leave a directory with permissions greater than 755.

Step Three:
Run Upgrade - this is essential.
In your browser go to
http://www.example.com/wp-admin/upgrade.php or
http://www.example.com/blog/wp-admin/upgrade.php
(It depends how your site is set up).
Now wait a while, especially if you have a large blog.

Login. See anything too funky ? Press CTRL and F5 to hard refresh (on a Windows machine) or Apple+R / Shift+Refresh (on a Mac)

Upload a blank text file. Rename it to ".htaccess" and CHMOD (set it's permissions) to 666, then when you are logged into the blog, go to Options > Permalinks and Update.

That should be it ....

Troubleshooting:

Can I have the new editing toolbar and quicktags at the same time ?
No. But Owen has written a plugin that enables you to easily add buttons to either editor - more information.
Where do I put my custom quicktags.js ?
/wp-includes/js/
Can I check if my plugins work before upgrading ?
Yes - Matt's Plugin page
How do I get my custom smilies to work in this version ?
Follow this guide which uses wp-config.php
Can I change back to 1.5.2 ?
If, and only if, you have a complete database copy and all your 1.5.2 files.
Feature 'X' doesn't seem to work.
Please post to the forum with the location of your blog, your webhost, the OS you are using and the browser and browser version you are using. If you just say "This is bust" you will get no help.
Upgrading looks scary, will someone do it for me ?
Probably - post to the forums and ask :)
Can I change the blue colour in the admin ?
Right now, only if you use the Spotmilk Admin Theme
There are a few of us that use the blog, and we don't all want the new editor
Go to Users > Your Profile and scroll to the bottom to set your choice
Can I make multi-blogs from this version ?
No.