The error was “Warning: Attempt to assign property of non-object in /path/to/wp-content/link-template.php on line 999″

The offending code looked like this:

if ( empty($post->post_title)  )
$post->post_title = $previous ? __('Previous Post') : __('Next Post');

Even though the theme the site is using didn’t have a custom Image Attachment Template (image.php), the default theme does, so it led me to believe the issue lied with the core files.  Essentially, it seems as though the post object wasn’t being set, and since I haven’t yet had the time to delve into a more proper method for resolving the error, I simply changed the if conditions to the following.

if ( empty($post->post_title) && !is_attachment() )
$post->post_title = $previous ? __('Previous Post') : __('Next Post');

That cleared the error so at least I can get on with my life, and look into the real source of the problem when some free time shakes loose, preferrably before the next WordPress Upgrade boils the error back to the surface.

Install Ubuntu

Download Ubuntu.    By default, the button downloads the 32-bit version.  If you need 64-bit, or a version other than the one listed, click on the Alternative download options link to expose more options.  When it’s done, you should have an disc image (.ISO) of the installation media on your hard drive.   If you are installing on a blank computer rather than a virtual machine (VM), you will want to burn that .ISO to a CD.  In Windows 7 it’s part of the native functionality, but explaining how to do that is outside the scope of this article.

Next we need to insert the media into our VM so it is available for installation.  The easiest way to accomplish that on a brand new VM is just to go ahead and start it.  You can do this by double-clicking the name of the VM in the main VirtualBox window.  This will prompt you with the First Run wizard.  Click next to pass the welcome screen and you will arrive at the Select Installation Media screen.

CD/DVD-ROM Device should be selected by default.  If not, make it so.  Under Media Source, click on the folder icon to the right of the drop-down.  This will launch the Virtual Media Manager with the CD/DVD Images tab selected.

Click on the Add icon and browse to, then select, the Ubuntu .ISO you previously downloaded.  This will close the Virtual Media Manager and return you to the First Run wizards Select Installation Media screen.  Note the Media Source.

Clicking Next will take you to a summary page.  Click Finish to begin booting the VM with the selected installation media.  The Ubuntu install should begin almost immediately.

Use your arrow keys to select your language, then hit enter.  At the resulting menu, select Install Ubuntu.  This will load a GUI installer for Ubuntu.

I have to tell you, the Ubuntu installation is about as easy as OS installations can get. Select your Language, timezone, keyboard preferences, partitioning scheme, enter your user information, and let ‘er rip. For me, the timezone and user information screen were the only two I needed to provide meaningful input for, the rest were good by default.

When it’s time to restart the machine you will prompted to remove the installation media. You can do this easily enough from the VirtualBox menu at the top of the VM window; Devices => CD/DVD Devices => Unmount CD/DVD Device. At the point, you can safely reboot by pressing the Enter key.

Once the VM comes back up, and you’ve logged in to your new Ubuntu installation for the very first time, the first thing you will want to do is install any update that has been published for your version. Do this through the GUI by navigating the System menu at the top left of your Ubuntu interface (System => Administration => Update Manager), or through the command line by bringing up a terminal window (Applications => Accessories => Terminal) and entering the following commands:

The dollar sign is not part of the command but is displayed to indicate the start of a new line which will be helpful when my examples start wrapping.

$ sudo aptitude update
$ sudo aptitude upgrade

As soon as that is finished, you might have/want to reboot the virtual machine.

$ sudo shutdown now -r

Our next step is installing the VirtualBox Guest Additions which are a set of tools designed to make interacting with your new VM a whole lot easier. Using the VirtualBox menu, select Devices => Install Guest Additions… or simple press your Host key and the D key together (Right CTRL + D by default). This will mount the Guest Additions CD and probably prompt you with a worthless auto-play window. Go ahead and cancel out of that, and return to your terminal window.

For 32-bit systems:
$ sudo /media/cdrom/VBoxLinuxAdditions-x86.run

For 64-bit systems:
$ sudo /media/cdrom/VBoxLinuxAdditions-amd64.run

Time for another reboot.

$ sudo shutdown now -r

Once it is back up, your are ready to continue on to the next step. However, if you are thinking you might want to share folder between your Host machine and your VM, it might behoove you to take a peek at this article I wrote on folder sharing. Otherwise, continue on to Step 3: MySQL, PHP, REE, and nginx via source through Passenger!

While much of this is specific to my particular requirements, this would be a good starting point for anyone looking to get their feet wet with PHP and/or RoR application development.  It would also be a good starting point for people interested in familiarizing or re-acquainting themselves with Linux, as Ubuntu is about as newb-friendly as Linux distributions get.

I should also note that even though I’m installing this as a virtual machine, it would work equally well on a real machine without the use of VirtualBox.  If you are going that route, or you are familiar with creating new virtual machines, then skip the first step altogether and go on to part 2.

Create the Virtual Machine

Install the latest release of VirtualBox for your existing platform.  The latest version at time of writing was 3.1.2.

Once installed, launch VirtualBox. From the Machine menu, select New (or press CTRL+N) to start the  Create New Virtual Machine wizard.  Click Next to continue past the welcome screen to the Name and OS Type selection screen.

Enter a descriptive name (like UbuntuDev) in the text box provided, and choose Linux from the Operating System drop-down.  After selecting Linux, the drop-down for Version automatically changed to Ubuntu on my version of VirtualBox.  If you are running a 64-bit host operating system with an architecture that supports VT-x or AMD-V virtualization technologies, then you can change the Version to Ubuntu (64 bit).  If what I just said made you dizzy, you aren’t sure how to check, or you might be exporting the VM for use on a computer you are unsure of, then leave the Version as Ubuntu.  There is no significant difference for our purposes, but make a note of which you selected so that you know whether to be downloading 32-bit or 64-bit binaries as we go on.   Click Next to continue to the Memory screen.

Select the amount of memory (RAM) you’d like to dedicate to the Ubuntu VM.  A good rule of thumb is to assign less than half of your computer’s physical RAM to your VM, but you should never need more than 2GB (2048MB) for this sort of appliance.  In fact, 1GB (1024mb) should be more than enough.  Also, keep in mind that this RAM is only used while the VM is running, so it’s not like you have to be overly stingy either.  Click Next to continue to the Virtual Hard Disk screen.

The Virtual Hard Disk screen is cake, assuming that Boot Hard Disk (Primary Master) is checked, and Create new hard disk is selected, you can click Next to spawn the New Virtual Disk wizard screen.  At the Welcome screen, click Next to continue to the Hard Disk Storage Type selection.

Another easy one, choose Dynamically expanding storage, and click Next to continue on to the Disk Location and Size screen.

The Location field should be auto-populated with a variation of the name you chose for this VM, but feel free to change it if you like.  The Size warrants some consideration.  First, an explanation; virtual disks are represented individually as single large files on your hard drive.  Had we chose Fixed-size storage on the previous screen, then whatever value we enter here would determine the size of the corresponding file.  However, since we chose Dynamically expanding storage, the size selected here only represents the largest possible size the virtual drive could consume, but in reality the file stored on our physical hard drive will be much smaller.  In this specific case, it will be less than 5GB after we’ve installed everything.  In addition, running out of space is kind of a pain to rectify, so we definitely don’t want to be stingy.  Mine defaulted to 8.00 GB, and even though I know that will be enough room for this VM’s intended purpose, I doubled it to be safe. Tripling it works too, or even quadrupling it since it is very unlikely that this VM will ever need that much space, and it will likely sit below 10gb for the duration of it’s lifespan.  Once you’ve selected a size, click Next to see the virtual disk summary screen.  If everything looks right, Finish to return to the virtual machine summary page.

Review, and when ready, click Finish there too.

Need a break?  Take one, otherwise you can continue on to Part 2 – Installing Ubuntu.