I’ve done a fair bit of WordPress troubleshooting over the last few weeks, including moving sites from one server to another and upgrading server operating systems. While a lot of this isn’t probably that interesting, I did come across a few things that might help other people undertaking similar tasks.
My method for moving content between sites generally involves exporting the content to XML, installing a fresh instance of WordPress on the new server, importing the content using the WordPress Importer plugin, and then seeing what doesn’t work. What usually doesn’t work is uploaded images and files, but it’s just a case of copying across the whole contents of /var/www/html/wp-content/uploads to the new server to fix that.
Talking of which, Debian (and derivatives) changed the default location for websites from /var/www to /var/www/html last year. If you upgrade Debian to the latest version and all your WordPress sites break, then it should just be a case of editing /etc/apache2/sites-available/000-default.conf so that the DocumentRoot value is set back to to /var/www/.
My last revelation is around hardwired links. When moving a site to a new server (with a new URL) there are likely to be many references to the old site URL in config files and in the WordPress database. There is a plugin called Search and Replace which does all the heavy lifting for you, and which should rewrite your new URL to everywhere it needs to be. I’ve used this a few times now and it works really well.
I’m also half way through writing up how I install sites from scratch, but that’s going to be quite a lengthy document and probably deserves a separate post.