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Linux is blessed with a variety of methods for accessing, expanding and building dynamic, scalable storage solutions. And they’re not just for industry experts either – even everyday Linux users can get access to a great deal of functionality by sharing and accessing data across a network.

Set up iSCSI and your data will stream from your PC like a magical rainbow. Perhaps. If you’re very lucky.

But there’s a new generation of solutions that can increase performance, offer more features and improve security – one of which is iSCSI. As its name implies, iSCSI is a version of the SCSI protocol, which is responsible for shuffling data between various SCSI devices. The key difference with iSCSI is that instead of transporting data across local cables and buses, the ‘i’ takes that data across the internet or your local network, attaching remote storage devices to your local system. It’s perfect for storage area networks (SANs) in particular, and you’ll find network administrators in enterprises of all sizes singing the praises of iSCSI’s ability to combine big-business fibre channel commands with generic networking hardware, saving their departments thousands of pounds in both hardware and infrastructure costs. iSCSI is also a great general-purpose remote storage solution that could easily replace the NFS protocol.

Understanding iSCSI

You can now find iSCSI in many network-attached storage (NAS) devices for the home and even standard Linux installations. This is because it’s a great storage protocol for an expanding network. It might be hard work to master, but you can build a working configuration with relative ease. The great advantage that iSCSI has over some of the alternatives is that drives are exported as block devices, just as blocks of data would be transported over an old SCSI cable. This means that, to the Linux kernel, these drives are handled exactly like local block devices. This makes it perfect for connecting the storage area of a database to the client application or, more recently, the virtual storage devices used by VMware and VirtualBox virtual machines. It’s also ideal if you want to run a machine without any local storage – traditionally the domain of NFS.

Use ‘apt-get install iscsitarget’ to add the appropriate packages to your installation.

Before getting started, your first step should be to familiarise yourself with some of the concepts that are used by iSCSI. These appear to take their names from the Terminator films, with the two most important being the Initiator and the Target. The Initiator is the iSCSI equivalent of the client. It’s the machine you want to have access to the remote data – the one that’s running the applications, or your desktop. The Target is the place the Initiator grabs the data from – another machine running the iSCSI server software and managing the requests to and from the storage medium. You’ll often find NAS drives running the Target server, for example, and you’ll only need to run the Initiator on your local machine in order to access the Target drive.

Set up the Target

It’s possible to share a large variety of different storage types over iSCSI, but the easiest to configure are entire drives. iSCSI connects devices at the block level, which means the job of partitioning and formatting can be left to the Initiator rather than the machine that’s attached directly to the hard drive. On our system, the drive we used was listed as /dev/sdb, and we’ll stick with this example throughout this tutorial. The system drive is normally /dev/sda. To find out what yours is, type fdisk -l on the command line for an overview of what’s connected to your system.

Edit the configuration file in nano. You’ll need to add a line which ensures iSCSI is switched on.

On the Target machine, you first need to install the ‘iscsitarget’ package. You can do this either from the Synaptic package manager or by typing sudo apt-get install iscsitarget on the command line. This will also install several configuration files, and the first of these that we need to look at is ‘/etc/default/iscsitarget’. You can type sudo nano followed by the path to the file name to edit it on the command line, or use your favourite desktop editor if you prefer. We only need to make a single edit here – making sure ‘ISCSITARGET_ENABLE=true’ is the only line in the file. Nano users need to press [Ctrl]+[X], then [Y] to save the changes.

Edit configuration files

The next file we need to edit is ‘/etc/ietd.conf’, which you’ll need to open in an editor. This document contains a working configuration, with lines using the # symbol designated as comments and therefore out of action.

The first line we need to edit defines what’s known as the iSCSI qualified name, or IQN for short. Just search for Target, followed by iqn. As with pages on the net, this IQN name has to be unique to your installation, and it takes the form of ‘iqn’, followed by the year and month, then a reversed version of your domain name. This is then followed by a colon and a reference to whatever you’re going to call the target storage device. This can be anything you like. Here’s what we chose:

iqn.2010-01.com.example:storage.disk2

Next, we need to define the drive that’s going to be shared over iSCSI. Remove the # symbol from the line starting with ‘Lun’ and modify it to read Lun 0 Path=/dev/sdb,Type=fileio. You need to change ‘/dev/sdb’ to the location of the drive that you’ve decided to share. Next, uncomment the Alias line at the bottom of the current section and save the file.

You’ll need to do some deeper editing to the ‘/etc/ietd.conf’ file.

You may have noticed that there are two lines available for a username and password, but we’re going to leave these untouched for now because we’re running our iSCSI device over a trusted network. You can always come back to this point and change the configuration after you’ve got the basic connection working, if you think that you need to.

To enable the device to be shared, open ‘/etc/initiators.allow’ and add iqn.2010-01.com.example:storage.disk2 ALL. When you get the connection working, you’ll need to change ‘ALL’ to the IP address of the machines allowed to access your iSCSI device, but for now we’re trying to remove all obstacles that could stop us getting the connection working. Start the Target server by typing sudo /etc/init.d/iscsitarget start.

Set up the Initiator

It’s now the turn of the other machine, the Initiator. To begin, you need to install the ‘open-iscsi’ package. Once that’s done, open the ‘/etc/iscsi/iscsid.conf’ configuration file and look for the line starting with ‘node.startup’. Change the default value of ‘manual’ to automatic, save the file and restart the service by typing sudo /etc/init.d/open-iscsi restart.

Make sure you change the node startup option to ‘manual’.

Almost everything is now configured and ready to go. Our next step is to probe the Target machine to see what storage services it offers, hopefully listing our drive in the process. Type iscsiadm -m discovery -t st -p, followed by the IP address of the Target. You can find this by typing ipconfig on the Target machine. If everything is set up correctly, you should see the IQN of your drive as output to the iscsiadm. This is the output we received:

iscsiadm -m discovery -t st -p 192.168.1.61
192.168.1.61:3260,1 iqn.2010-01.com.example:storage.disk2

Now you know that the Target machine is correctly configured and that iSCSI can see the remote storage device, you need to type iscsiadm -m node. This will automatically create configuration files within /var/lib/iscsi/nodes for the storage unit on your local machine, which will allow the Initiator to mount the device automatically when the service is restarted. You may need to do this manually by typing sudo /etc/init.d/open-iscsi restart.

The remote drive should now be mounted locally. The best way to check is to type fdisk -l to list all the storage devices attached to your machine. The iSCSI drive should be part of the output, but you won’t see any indication that it’s being connected over a network. That’s the great advantage of using iSCSI.

Mount the drive

iSCSI passes the block information, so you need to format the remote drive from the Initiator machine before it can be used. This process is exactly the same as partitioning and formatting any other drive on your system. You could use fdisk on the command line, for example, or you could take the easy route and use a graphical partitioning tool like GParted, which you can install through your distro’s package manager.

After launching GParted, you first need to select the remote drive from the dropdown list in the top-right of the main window. As with fdisk, the iSCSI drive looks exactly like a local drive, so you need to take special care to select the correct device. You can lose data from other drives permanently with GParted, so proceed with caution.

If you’re hooked up to your target drive you should be able to treat it like any locally connected module – including partitioning it.

With the remote drive selected, click on the large grey area in the middle of the window marked ‘unallocated’. This is the unpartitioned area on your remote drive. Click on ‘New’. By default GParted will use the entire disk, but you’re free to subdivide the remote drive in exactly the same way you would a local one if you prefer. Leave ‘Primary Partition’ selected, then select ‘ext4’ as the filesystem and give your drive a meaningful label before clicking ‘Add’. Click on ‘Apply’ to make the changes to the remote drive, and then simply sit back and wait while the formatting process finishes.

Now that the drive is correctly formatted and partitioned, it’s time to mount it onto the local filesystem so you can start reading and writing data to it. You can use the ‘mount’ command to attach the drive just as you would any other, but there’s one small difference that you have to consider whenever you use multiple iSCSI devices – they might not always have the same /dev path. The solution is to navigate to the device using the /dev/disk/by-path/ nodes, so you can be sure you’re getting the same disk every time.

If you type ls /dev/disk/by-path, for example, you can easily see which devices are using the IQN address. In our example, we mounted the remote drive onto the local /mnt/iscsi folder with the following commands:

mkdir /mnt/iscsi
mount /dev/disk/by-path/ip-192.168.1.61\:3260-iscsi-iqn.2010-01.com.example\:storage.disk2-lun-0-part1 /mnt/iscsi

You can now read and write files to the /mnt/iscsi mount point, and these are passed directly to the remote drive just as if they were connected using an extremely long SCSI cable.

iSCSI on NAS boxes

Two of the trickiest parts of using iSCSI are finding the hardware and configuring the Target machine, but luckily there may be another option if you have a Linux-based network-attached storage box. Many of these will offer up a chunk of the storage inside the box over an iSCSI connection, and you can usually activate and configure this facility with just a couple of clicks. Some of these will let multiple Initiators access a single target and enable you to add CHAP password authentication. Then it’s simply a case of running the iSCSI discovery procedure on your Initiator hardware. If you’ve chosen to use a password and username, you’ll need to run the ‘iscsiadm’ command on the Initiator to add those values to the configuration file for that Target. The command takes the following format:

iscsiadm -m node --targetname IQN --portal IP AND PORT OF TARGET --op=update --name node.session.auth.

You need to run this three times, changing the end parameters each time. With the first execution, add authmethod –value=CHAP to the authentication check. For the second, add username –value=username to specify the username for the connection, and for the third execution add password –value=password to specify the password.

Create a virtual hard drive

Many more technical distributions, such as Fedora, use logical volume management (LVM) for local storage and filesystems. One of the advantages of LVM is that you can shrink, expand and create partitions on the fly from the pool of storage on your machine. Logical volumes can be used for all sorts of tasks. Virtual machines often use them to keep data from the main system, and they’re handy if you enjoy playing with filesystems. They’re also useful if you want to try iSCSI, because you don’t need to have a spare hard drive – you just need the space within your logical volume pool.

The key to adding new virtual drives is the ‘lvcreate’ command. We used the following command to create a 10GB logical volume: lvcreate -L10G -n vdrive vg. This creates a volume called ‘vdrive’ in a volume group called ‘vg’. You’ll need to take a look in your /dev directory to discover the name of the logical volume group used by your installation. After creating the drive, it appears in the /dev volume tree just like any other device and you can share it across the iSCSI connection like a real hard drive.

Even without LVM, there are other options for dynamically shared storage. You could create an image file, for example, by typing dd if=/dev/zero of=/mnt/iscsi.img bs=1024k count=1000. The ‘count’ value is the size of the image, while ‘/mnt/iscsi.img’ is the file that’s created. You can use that path as the source for the iSCSI Target on the ‘Lun 0’ line in the ‘/etc/ietd.conf’ configuration file, and use it like a real partition.

Virtualisation

iSCSI is commonly used by cloud applications and the world of virtualisation. This is so you can access the same hard drive data regardless of where the virtual machine is running. If you’re in the market for a major, enterprise-grade virtualisation solution that uses iSCSI, take a look at VMware’s ESXi solution, which is available for free from www.vmware.com.

Boot options

If you want the Target iSCSI device to be available each time you boot the Initiator machine, you will need to add the remote device to the ‘/etc/fstab’ file. The quickest way to do this is to copy another line in the file and change the parameters to suit the iSCSI device. Make sure the path uses the ‘by-name’ format so that you can be sure you get the same drive at each boot.

Tags: application, authentication, business, database, desktop, device, directory, Discovery, functionality, generation, Hardware, industry experts, information, Internet, ip address, linux, Nano, network, Networking, parameters, partition, performance, security, Server, Software, space, storage, storage service, system, type, virtual machine, virtualisation, vmware, XP

There’s a delightful story that does the rounds regarding one of the founding fathers of Linux. It’s said that during the early days of the open-
source operating system’s development, this fellow took to attending conferences in complete silence. All attempts to communicate via means other than hand gestures were refused. Instead, he pointed at things.

Apocryphal or not, the tale remains highly relevant today. Our hero’s beef was with the windows-based graphical interface metaphor and its knack for turning us into mouse-pointing morons. Fast-forward a decade or two and astonishingly little has changed. The windows GUI has, you might say, proven to be extremely gluey.

The classic case study is Microsoft’s eponymous Windows OS. Admittedly, early versions of Windows would seem pretty alien to today’s users – but that’s an illusion. Look past the clunky graphics and Windows 95 is largely identical even to Windows 7, Redmond’s latest and greatest OS. Icons, taskbar, the folder metaphor – all are essentially the same as they were 15 years ago.

That’s a long time in any industry, but it’s an absolute eternity in information technology. Along the way, Microsoft has flirted with a few interesting new features. Early betas of Vista included widespread use of virtual folders and the promise of a fully vectorised and hence scalable graphical interface, for instance. But in the end, the retail build of Vista was yet another reskin of Windows NT, just a bit prettier.

Linux and Apple’s Macintosh operating systems have scarcely been any more innovative. More user-friendly and configurable? Perhaps. More polished? Certainly. But both remain firmly rooted in the window-juggling keyboard-and-mouse camp.

Compared to the enormous advances made in computer hardware, it’s all a bit bizarre. Back in 1995, a single-core Pentium processor running at 100MHz or so was your lot. That’s an in-order 3.1 million transistor chip with 8kB of cache memory, for goodness sake. Today, we’re up to six cores, multiple GHz, over a billion transistors and cache pools nigh on double-digits in MB.

If you think that’s merely a matter of scale rather than a new paradigm per se, what about features such as virtualisation or hardware-accelerated 3D graphics? That’s to say nothing of the rapid rise of LCD monitors and more recently solid-state drives. By any sane metric, computer hardware has been in a constant state of revolution. It’s utterly relentless.

So, not to put too fine a point on it, what gives with GUIs? The answer, frankly, is that I don’t know. Over the years, I’ve visited several labs dedicated to advanced interface research, including those of Microsoft and Intel. I’ve even interviewed luminaries from the heyday of interface research, including some who worked at the fabled Xerox PARC lab in Palo Alto. The very people who invented the GUI, in other words. In fact, I reckon I’ve spoken to all the right people. I’ve played with all the latest table-top, touchscreen human-machine interfaces. But I remain essentially clueless. Nothing I’ve seen or heard of is obviously the next big thing.

At this point, Apple’s iPad inevitably hovers into view. A remarkable device in many ways, it’s no good for data input or content creation and therefore doesn’t offer a plausible alternative for desktop computing. However, what it does is underline just how painful the Windows interface is. Once you’ve danced around a few of your favourite websites courtesy of the iPad’s delightfully responsive screen, the scrolly-scrolly, pointy-clicky PC experience seems pretty laughable.

Even a good smartphone can make the PC feel clumsy; I often prefer reading emails on mine. Replying to them is out of the question, but as a viewing device it’s very pleasant and provides temporary relief from what is becoming an overly familiar and oppressive desktop computing experience. You could say the differences are largely arbitrary, but trawling emails on my phone feels like a break from work. That’s got to say something about the tiredness of the windows metaphor.

Tags: API, Apple, Computer, Computing, cores, desktop, Development, device, email, Ghz, Hardware, information, Information Technology, interface, linux, Macintosh, memory, microsoft, Operating Systems, processor, Research, system, Technology, transistor, virtualisation, Vista, web, Windows, XP

The future of scalable, distributed computing is in the cloud. This is a nebulous concept that’s supposed to describe a cloud’s perpetual elasticity in providing online storage, processing and bandwidth. There are user-facing cloud services such as Google’s web-based applications, the Ulteo online desktop and Canonical’s One service for silently cross-computer folder synchronicity. And there are the more ambitious services of Amazon’s EC2 platform, enabling websites like Facebook to expand and contract their resource requirements in realtime, catering for peaks and troughs in demand and only paying for the capacity and the CPU cycles it actually uses.

Tux: the ideal combination of experienced mountain climber and feathered networking expert.

This latter kind of cloud is a big enterprise oriented subject, and Facebook-like scenarios are way off the scale when it comes to the ordinary Linux user. But Linux is at the heart of many of these installations, and there’s plenty of enterprise cloud technology left lying around for us mortals to play with. Incredibly, considering it’s user-friendly approach to Linux, that includes the latest release of Ubuntu.

Ubuntu 9.10 bundles something called ‘Eucalyptus’, an open source tool for generating private clouds that can dynamically connect to Amazon EC2. Eucalyptus, an acronym for ‘Elastic Utility Computing Architecture Linking Your Programs To Useful Systems’, originated as an ambitious project run by the Computer Science Department at the University of California. But it quickly became apparent that the technology it was developing was in great demand, and professor Rich Wolski, as well as many of his students took sabbatical leave from their day jobs and founded Eucalyptus. So far, they haven’t gone back.

STEP 1: Getting Started

Before trying Eucalyptus for yourself, there are some demanding requirements. Installation is relatively straightforward, but you will need to use the Linux command line, and possibly, troubleshoot any problems by reading the log files.

You will need at least two machines. One for front-end management and another to act as a single nodes on the cluster. Clouds like these rely on virtualisation to provide the elasticity and software scaleability of the hardware doing the processing. They run virtualised instances, called images, of your chosen operating system. In the case of Eucalyptus, virtualisation is handled by either KVM or Xen at the kernel level, which is why you need a VT-enabled CPU for the node machines, along with plenty of horsepower, memory and storage. It also means that you will need to configure your cloud to do something useful after you’ve got it working, just as you would a standard Ubuntu server installation.

You’ll be given the option of installing a new cluster or adding a node to an existing one.

The machine used to control and manage your cloud is usually referred to as the backend, and to get started you need to insert the Ubuntu 9.10 Server into its drive and reboot. When you see the boot menu, select a language followed by ‘Install Ubuntu Enterprise Cloud’. Choose language, location and keyboard layout, then enter a host name, we used ubuntu1. The next step will ask whether you want to create a ‘Cluster’ or a ‘Node’, and you need to select the first option, ‘Cluster’.

You will then need to work through the standard Ubuntu partition options. Ideally, use the entire disk for the installation unless you need to keep data on the machine, and leave the most options at their default values. The installer will then go off and create the partitions it needs then download and install a few packages. After this, it will ask for the default username and password for the machine, and whether you need your home directory encrypting. Skip the HTTP proxy question and leave the automatic updates off for now, and set Postfix to ‘No Configuration’.

STEP 2: Network and Nodes

We now have a couple of questions that deal specifically with the Eucalyptus configuration. The first asks for a cluster name, and you can call it what you like. This is the name people will see if they access your cloud. The second question asks for a range of IP addresses on your LAN that Eucalyptus can safely use to assign to each node. To answer this, you need to know the range of addresses that your router is using.

Many routers on a home network, for example, will issue IP addresses in the range of 192.168.1.2 – 192.168.1.100, or similar. You need to find this information from your router and enter a range that isn’t going to be assigned automatically from the router but is on the same domain. ‘192.168.1.100-192.168.1.200’ would work with our previous example. But for the sake of our experiment, you only need to find a couple of spare addresses on the same domain.

It’s best to assign a range of currently-free IP addresses to make up your cluster. It saves a lot of hassle later on.

After entering these details, the remainder of the packages will be installed and you’ll be asked to reboot the machine without the disc in the drive. When the backend reboots, login to your account. You should see the IP address for the server displayed and the message about documentation, and you need to make sure this address in within your network’s range.

It’s now time to tackle the node. Take the same disc you used for the backend and use it to boot your node machine. Choose ‘Install Ubuntu Enterprise Cloud’ from the boot menu again, and go through the first few questions. After entering a new hostname, you should be told that there’s already a Eucalyptus cluster controller on your network, and ‘Node’ will be selected automatically. Just press return. Installation will now be identical to the earlier install, only without any further Eucalyptus questions. Even your user name and password are grabbed from the backend machine, and at the end of the process, you can reboot and the node is now running.

STEP 3: Configuration

On each machine, you should login and type ‘apt-get upgrade’ to download and install the latest package updates for the system. You’ll probably have to reboot each machine again.

We now need to tell the backend about the existence of our single node. Login to the backend machine, and type ‘sudo euca_conf –no-rsync –discover-nodes’. You should see something like the following:

New node found on 192.168.1.62; add it? [Yn]

Just press return, and you should see that the two machines connect and synchronise a pair of keys that will be used to authenticate future connections. Now launch a browser from any other machine on the LAN and go to ‘https://backend_ip:8443’. You will get a security warning about the unverified nature of the certificate used for the connection, but you’ll need to add an exception for this site. Firefox will step you through this process automatically.

You should run the configuration tool as a super user.

You will then see the ‘Eucalyptus Enterprise Cloud’ login screen. Enter ‘admin’ for username and the password, and you’ll be immediately asked to enter a new administrator password, and check the IP address of the server so that a new certificate can be generated. After clicking submit, you’ll find yourself at the Eucalyptus management console, but before we can get stuck into the details, we need to download something called a credentials file, that we can use to authenticate our own tinkering with the server, as well as any other cloud service you may want to use to expand your installed.

STEP 4: Credentials

Click on the Credentials tab followed by the ‘Download Credentials’ button. This will leave you with a zip file that you will need to transfer to your user account on the backend machine. The easiest way is from the command line, using ‘sftp backend_ip’ to connect to the machine, followed by the command ‘put’ with by the path to the zip file, ‘put euca2-admin-x509.zip’ for instance. On the backend, you then need to unzip the file into a hidden folder in your home directory with ‘unzip -d ~/.euca euca2-admin-x509.zip’ and run the script it contains that configures various environmental variables and keys for managing the cloud, ‘. ~/.euca/eucarc’. This script will need to be run whenever you re-connect to your backend system.

Once it’s properly installed, Eucalyptus’ web interface looks after much of the heavy lifting.

To check that everything is working as it should be, type ‘euca-describe-availability-zones verbose’. The output should look like the following:

AVAILABILITYZONE pcp_cloud 192.168.1.48
AVAILABILITYZONE |- vm types free / max cpu ram disk
AVAILABILITYZONE |- m1.small 0002 / 0002 1 128 2
AVAILABILITYZONE |- c1.medium 0002 / 0002 1 256 5

This is important information. The critical data is beneath the free/max columns. This shows the CPU cores available on your cloud for immediate use. The more nodes you have on the network, the higher the number here. If you see only zeros, then there has been a problem with the node starting the appropriate controller, and you’ll need to check its /var/log/eucalyptus’ directory for the log files.

STEP 5: Run an image

It’s now time to create a virtual instance of a machine to run on our node. Eucalyptus makes this very easy because it allows you to download pre-built packages.

Go back to the browser and click on the ‘Store’ tab in the management console and choose a pre-built image to download. We opted for Karmic Koala (i386), which is a 174MB download. You will also have to wait a couple of minutes for the image to be installed after the download has completed, but before long you should see the message ‘How to run?’, and you’re ready to go. We did have problems with our backend machine hanging at this point, but we added more memory to the system and it worked though a hitch.

You’re provided with a selection of pre-configured virtual machines just begging to be run on your new cloud.

Before we go back to the command line, click on the ‘How to run’ link next to the download, and make a note of the ‘emi’ value at the end of the command. This is the unique identifier for the image, and we’ll need to use this when we run it. Back on the command line, type ‘touch ~/.euca/mykey.priv; chmod 0600 ~/.euca/mykey.priv; euca-add-keypair mykey > ~/.euca/mykey.priv’ to create a key pair to authenticate the connection to your running image. Then type ‘euca-describe-groups’ followed by ‘euca-authorize default -P tcp -p 22 -s 0.0.0.0/0’ to enable SSH access to the virtualised machine, and finally, type the following to launch it:

euca-run-instances -k mykey -t c1.medium emi

Replace the emi value with the identifier you took from the web interface. You should also notice that we’ve specified ‘c1.medium’ as the type of image, and this is a preset for the amount of resources the image is given. These can be viewed and modified using the Configuration page of the web management interface. It may take a while to initialise as there’s a lot of data being copied across the network, but you can check it’s status with the ‘euca-describe-instances’ command, and wait for it’s state to switch to ‘running’ rather than ‘pending’. On our hardware, this took about 20 minutes.

You’ll also see the IP address of the new instance, and you can now connect to your new cloud server by typing ‘ssh -i ~/.euca/mykey.priv ubuntu@ip_address’. You’re now ready to install and run your mind-blowing web 2.0 application!

See also: Amazon EC2

Private clouds, of the kind we’ve started to build above, are an excellent raw resource if you need a dynamic pool of processing power. But the beauty of cloud computing is that it’s designed to be elastic, and this means you needn’t be restricted by the physical limitations of your own setup. With Eucalyptus, for example, you can take exactly the same images you’re running on your local machines, and move them to Amazon’s EC2 service as and when you need the extra horsepower.

This gives you relatively unlimited resources in terms of processing power, storage and network bandwidth, and you only have to pay for what you need, rather than the old model of paying for a rack of servers somewhere that spend most of their time idle. Eucalyptus manages this by building an API that’s compatible with Amazon’s, making the images that you configure on your local network drop-in compatible with the images that run on Amazon’s servers. Also, the tools that you use to manage and maintain your private cloud are the same you use to manage an Amazon-hosted cloud, making the transition between the two almost seamless.

There are other advantages to this compatibility too. You can create, test and experiment with private clouds before committing your concept to the costs and scrutiny of a public cloud running on Amazon’s servers. And private clouds, such as the one we create in the main text, can give you an excellent feel for how the technology works, and how you and your company may find it useful.

Troubleshooting

As you might have noticed, despite the Ubuntu installation being the easiest way of getting a usable cloud system, it’s still far from easy. There are a lot of aspect to the configuration that can go wrong, from the hardware that you choose, to the network that the various machines are communicating across. Another problem is that the Eucalyptus project is only in its infancy, with Ubuntu 9.10 being the first distribution to include packages by default. This means there isn’t a great deal of support, especially if you’re new to the world of clouds.

But there are several things you can do to help solve problems yourself. Firstly, you should run ‘euca-describe-availability-zones verbose’ to check whether your node machine has been detected and added to the cloud. If you have zero resources available, then it hasn’t. The most common cause for this problem is that the synchronisation of the keys from the backend to the node has failed, stopping the node from registering itself. Check ‘/var/lib/eucalyptus/keys’ on both machines to make sure the keys are available. If the keys on the backend are missing, trying running ‘/etc/init.d/eucalyptus-cc-registration restart’ to regenerate the keys, then then try to add the node again using ‘euca_conf –no-rsync –discover-nodes’. If all else fails, try ‘sudo /etc/init.d/eucalyptus-sc-registration restart’ too.

We also had problems trying to register nodes after updating the system with new packages. The solution to this problem is to either add nodes to the cluster before you update any packages, or leave your installation with the packages include with the default install. This shouldn’t matter for an experimental installation. Finally, if all else fails, trawl through files within the /var/log/eucalyptus directory on both machines, as this should give you some idea of where your setup may be failing.

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