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Wordpress upgrade turned out to be quite difficult for a beginner like me. All the Wordpress files have to be replaced manually, and there’s no such thing as automatic script which can do the upgrade seamlessly for us. I have tried to follow the upgrade instruction carefully, nevertheless I was shocked to find out that all my permalink pages were gone, leaving 404 error message! Luckily later I found out that the problem was due to missing .htaccess file, and all my permalink pages were back up after the missing file was restored.
Other than that, I didn’t encounter many problems during the upgrade process, except some small problem while I was performing mysqldump to backup my Wordpress database. For those who want to perform the same upgrade, I would recommend you to read all the upgrade instructions carefully, and don’t forget to backup all your Wordpress files before you replace the files.