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Now that we have a raid array created, we are going to create some virtual drives. Why virtual drives? Well, we have one large terabyte drive right now, and if we just put folders in there, it can quickly get cumbersome. You have no control on size of those folders, and permissions can be more difficult. And if you try to share this drive, you can’t assign different drive letters in windows to different folders, just one to the drive. One other issue is file system. I am going to use just a basic file system here, but in the past I have created different file systems based on the type of use ie. large video files, small text files, etc. Making those decisions is beyond the scope of this tutorial, and I have decided that for my purposes now, it doesn’t matter that much. You can decided differently.

What we will discuss is using LVM. This enables you to set up virtual drives that can contain different file systems, and that can be grown and shrunk (usually) to fit the space needs of the system. We will look at maintenance of these file systems at a later tutorial. Here we will create a backup, and a pictures virtual drive. We will not use the full terabyte of space, so that we can grow these as needed, or add another for say music at another time.

I will once again be doing this on an ubuntu system, but the use of these tools is fairly standard across linux distributions.
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We are well into this whole patterns thing now, picking up lots of new lingo, and becoming better at communicating with other developers. Next on the list: the observer pattern. This is an important pattern to use to help prevent tight coupling and keep code separated into discrete objects. This pattern allows communication between two objects at particular times without each object needing to be too tightly coupled to the other.

The Observer in the Physical World

The idea behind the observer is like a subscription. Do you have a newspaper or magazine subscription? Have you signed up for cell phone texts from your favorite band when they have new tour dates? The act of you signing up with the newspaper, the magazine, or the band, is you saying you want a subscription, or that you want to become an observer. When the subject (newspaper, magazine, band) has something new to share (on a schedule or not) they run down their subscriber list, and notify the observers by mail, or text.

The Observer in the Software World

On the software side, the idea is the same. Your subject needs to provide a way to take subscriptions, hold a list of observers, and when a particular state changes, notify them. There is usually a couple of methods on the subject that takes in an interface that is used for getting on or off the subscription list. On this interface is also the “call back” method. This is the method that the subject will execute when it wants to inform the observers of state changes.
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We have looked at the Factory, the Adapter, and the Singleton patterns. Now we look at the Decorator. The Decorator is similar to the Adapter, but with a subtle difference. With our ReptileAdapter, we wrapped the Reptile class to map the interface methods of Animal to the appropriate methods on Reptile. With the Decorator we also wrap a class, but to add functionality, not to map it or replace the functionality.

The Decorator in the Physical World

The idea behind decorating things in the real world is pretty much how it sounds. We wrap an object with new functionality, while keeping the old functionality. How about a camera in a waterproof housing? When closed up, we have added the functionality of waterproofing, but we still provide a way to press the buttons and turn the dials so that the camera can be operated.

The Decorator in the Software World

On the software side, the idea is the same. It is usually used when we have one object that we like how it functions, but we want to augment the behavior for a different situation. Done correctly, we can keep inserting one object inside another adding functionality at every step.
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The last pattern we looked at was the Adapter pattern. It was a good pattern to start with as it maps well to the physical world and is fairly simple. Now we will look at the Singleton pattern. In some respects it is the simplest of patterns, but there are some things to think about.

The Singleton in the Physical World

The idea behind the Singleton is to ensure that there can be only one (insert Highlander jokes here). If you had a factory that made widgets, you would want a widget to be created many many times. But there is only one factory. If you were modeling the US government, you would only want one president. Only one senate.

The Singleton in the Software World

On the software side, the idea is the same. It is usually used when we only want one set of configuration variables, one controller, one data base connection pool, that kind of thing.
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Annotations allow you to attach metadata to a field, class, or method. Metadata is data that describes something else. For example, metadata about a song in mp3 format could be the artists name or the bit rate it was encoded at. A jpeg image could have metadata that described the image height or the number of colors in the image.

What do they look like?

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@Override
public String getName() {
	return "no name";
}

The word after the ‘@’ is the Annotation. It precedes a method or class name. The Override annotation is built into Java. It is used to indicate that a method overrides a parents method. These are used for compiler hinds, for documentation, and to apply meta data.
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This is part of our series on building a NAS. In this article we will get the box set up with a static IP address, and get your drives set up for RAID 1.

We are assuming that at this point you have Ubuntu installed. We are gong to install software raid in a moment. The first thing I want to do is make sure we have a static ip address. Usually Ubuntu will start up with a dynamic ip address. This can make it more difficult to transfer files to this box, so lets make it static.
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To me it seems a better word would be Specifics. The use of Generics is applying a specific type to a class that can be used in a generic way. One of the most common generic classes is List. A list allows you to put any type of Object in to it. In fact, you can put several different types of Objects into a List. But, there is a way to create a specific List type that can only take one type of Object.

What do they look like?

Since we are talking about Lists, lets look at what a ArrayList would look like that could only take Strings.

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List aList = new ArrayList();

What goes between the <> is the type that you want to specify for the List. You need to do it in the left side declaration, and on the right side where you are creating the Object.
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I don’t want to get too deep into every little thing in the collections classes here. In fact, you already know a fair bit about them, because we have used them with some of our Animal class examples. This is more an overview of some of the basic Collections classes.

What do they look like?

There are three main types of collections: Lists, Maps, and Sets. Technically you could try to argue that Map doesn’t extend Collection, so therefore it is not a Collection, but I think of it as part of the group.
They are used for groups of objects, or exactly as its name would imply, collections of objects.

List

A List is just that, a list of objects. The List interface provides a way to add, remove and get objects from a list. It however is just an interface. ArrayList is one of the more popular concrete collections that implements the List interface. Each implementation of the List interface may behave slightly different, but once you understand how a List works, you have a good start on understanding any List.
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I am not sure why I was acting to ridiculously. When version 2 came out, I was super psyched, then I found out that if you wanted to use the Dodge and Burn tool, Aperture would make a copy, and send you to the plugin. If you had made any adjustments before this, you couldn’t tell anymore, all the sliders would look reset. It bugged me that the dodge and burn plug in wasn’t non destructive. So… I ignored it.

Just recently I came across an image (can’t find it now) that was adjusted with this plug-in, and I had a “what the heck” kind of moment. I immediately fired up Aperture to re-check out this tool. To get to the plug-in, right click on an image, select Edit With… and pick Dodge and Burn.

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I had all kinds of trouble getting Zenphoto to install on 1and1. None of which I believe are the fault of the Zenphoto project. I am blaming the difficulties on how you need to configure php on 1and1.

What problems did I have. It appears that there were tables that were not created correctly. The way I figured this out was that I was trying to save a ¬†guest user and password to¬†and album. The name wouldn’t stick. When I went in and look under the MySql admin¬†tool (phpMyAdmin), there was no user field in the albums table. Something was wrong right from setup.

So here are the steps that I came up with to get zenphoto installed properly. I can’t say that all of the steps I took were necessary, and some might even be suspect, but in total it works.

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