How to install a simple highly available server with HA-OSCAR

In this post I will explain how to install a highly available server or in other words servers with a downtime of barely 0.001%. Computers crash sooner or later either due to some faulty component or as a result of a software bug, this tutorial will show how a simple server can be made nearly indestructible while costing near to nothing in requirement for technical knowledge.

The program I’ll use is HA-OSCAR, well simply because its free, open source, and lastly I know everything about it!

Ensure you get the following ready:

1. You have access to two computers that will be used as servers.

2. You are running at least CentOS4 or above.

Note: Portions of this tutorial in red text means it applies only to installation on a Rocks Cluster.

Download the three necessary HA-OSCAR packages available from XCR website to the computer that will be as the primary server

Create two directories “ha” and “rpm” in a “/tftpboot” directory

mkdir /tftpboot/ha

mkdir /tftpboot/rpm

Move the two repository haoscar packages “haoscar-repo-common” and “haoscar-repo-rhel” to your “/tftpboot/ha” directory

mv haoscar-repo-* /tftpboot/ha/

Untar these repository files that you moved in the previous step

tar xfvz haoscar-repo-common-*

tar xfvz haoscar-repos-rhel-*

Copy all the rpms from your installation DVD or all installation CDs into “/tftpboot/rpm”

cp /PATH/TO/DVD/RPMS  /tftpboot/rpm/

Move the main haoscar package still in your download directory to any path of your choice, preferable to your desktop. Untar this file.

tar xfvz haoscar2.0.tar.gz

Change directory to the resulting haoscar folder and run the installation script “haoscar_install” with your private ethernet port as an argument:

cd haoscar2.0/

./haoscar_install eth0

If installing on CentOS you will be asked to enter a mysql password, leave blank and press enter on the other hand if installation is being done on Rocks Cluster, you will be asked to enter the root password for mysql, type the root password then when prompted to enter mysql password a second time leave blank.

On completion of all these steps you will see the HA-OSCAR graphical installer come up.

Follow the steps shown in the installer as follows:

Install HA-OSCAR server

Build Image of standby server

Configure image of standby server

Setup Network boot and install Standby server

Complete Installation

Exit.

Warnings!

When creating an image of the server in step 2, ensure that no additional drives such as flash drives are connected to the image otherwise installation on your standby server WILL FAIL during partitioning.

Known Bugs

- When asked to enter root password for mysql, if you recieve a message saying “access denied” or such, ensure that you can start up mysql manually i.e

service mysqld start

if it is unable to start due to a timeout error then there exists a bug with your mysql installation. A similar problem is outlined here. Note that this problem occurs when you install rocks with some of the os disks provided by rocks cluster, if you use an official CentOS disk as your OS base disk installation goes smoothly.

My thoughts on Playstation 3(PS 3) Cell Processor and benchmarking results…

With the recent purchase of twenty one Playstation 3 console by my school, we were allowed to run programs (via linux) to make use of the massive computational potentials of it. Naturally, we wanted to find if it lived to the 204 billion floating point operations (Gigaflop) IBM claims it is capable of. The following charts show the results of various tests run on the PS3 by a third party and our own matrix computation tests in which matrices of sizes ranging from 100 to 100,000 was calculated:

From the chart we see the PS3 will excel in computations that require little memory use but high computation. Applications requiring high network data transfer rates might seek alternative solutions elsewhere also.

While the Sony Playstation 3 might not be known for its good line up of games, its introduction has led to the possibility of end users to own what might very well be a cheap supercomputer. It has been hailed as a true next generation multicore computer for its wonderful integration of Eight(8) Synergistic Processor Element(SPE) and Power PC(PPC) processors. Users can now exploit its massive power to write programs that are highly parallel achieving this for a fraction of the usual cost. The PS3 might seem like the ultimate machine when its potentials in the field of supercomputing is considered but it is not without its draw backs. The most notable of these being its memory limitations; it comes with 256MB of system memory and only 256KB of cache on each of its SPE cores. If these limitations are overcome, then its gigabit ethernet port might deter those seeking to string together a cluster of PS3s. A detailed report on the limitations of the PS 3 is available here. IBM has a good list of tutorials on programming the PS3. My source code for the PS3 benchmarking is available here

In a future post, I will compare the performance of other potential supercomputing machines like the Nvidia 8800GT and Tesla GPGPU which both use CUDA to achieve parallel programming.

Installing ha-oscar 1.3

In order to install HA-OSCAR, you must first download the three (3) necessary packages from the XCR group site.

1. haoscar-repo-common-rpms.tar.gz

2. haoscar-repo-DISTRO-VER-ARCH-1.3.tar.gz

3. haoscar1.3.tar.gz

Create a directory “/tftpboot/ha/ ” and copy the haoscar-repo-* files to this directory and extract.

Create a directory “/tftpboot/rpm” and copy all rpms present on the installation media into this directory.

Extract the haoscar1.3.tar.gz file in whatever directory it is stored and run the installation script.

High Availability Open Source Cluster Application Resource(HA-OSCAR) Project

In this post I will discuss my recent experiences with the open source community in the form of HA-OSCAR application. I was charged with the task of removing the OSCAR dependency in HA-OSCAR, thus making it a true high availability software.

With the world going for greener sources of energy and technology driving this green/renewable sources of energy immature, high performance computing(HPC) projects can be very high priced. Today’s HPC Projects take the form of massive data-centers which employ thousands or servers. PC World magazine in their December edition compares the power consumption of all the data centers to the whole state of Mississippi. With this cost ever increasing, a solution for running a low cost and low energy data center had to be implemented. This solution came in the form of clustering.

Clusters can simply be defined as several machines grouped together, all performing similar functions. It can also be referred to as parallel computing this is because all the computers are linked together via some network and act as a single machine. there are several types of clusters but one of particular interest to OSCAR is the “Beowulf” cluster. A beowulf cluster essentially comprises of a single computer referred to as the head node which controls some other number of systems which are called compute nodes.

Since the main idea behind the creation of clusters is cost and scalability, lots of issues arise regarding how reliable the off shelf components used to create it really are this is where high availability is introduced. HA-OSCAR seeks to greatly reduce the overall downtime of any server by simply creating an image of the server with the same exact configurations to be stored on another system which will be used as an alternate server in the case of an eventual failure of the main server. This alternate server is automatically assigned the role of the main server and resumes duties within seconds of failure of the main server.

During the lifetime of this project which will last from December 2007 to March 2008, I will have to do the following:

- Identify the core dependencies HA-OSCAR.

- Ensure that these dependencies are installed prior to an installation of HA-OSCAR

- Ensure that System Imager recognizes the disk controllers of a standby server prior to partitioning

- Upgrade System Imager, Installer and Configurator and integrate these with HA-OSCAR.

- On completion, extensively test in different environments.

As at this day Jan 8 2008, I am happy to say the project is 50% complete. The core dependencies identified thus far System Imager, System Installer, System Configurator, rysnc, dhcp server, xinet, httpd, mysql-server, and several perl dependencies have been successfully installed and is being currently tested as HA-Webserver, HA-OSCAR, HA-Rocks with the last two being cluster administration tools.

I will be making a post in the nearest future providing diagrammatic representation of how the HA application works and what has changed since version 1.2. Meanwhile, this link to OSCAR can provide more information about managing HPC systems, and this to HAOSCAR home.

Update: The project is finished!!. HA-OSCAR is now a true HA solution working with OSCAR and Rocks Clustering systems.

Configuring Ubuntu Gutsy for Sony Vaio with Thinkfinger Fingerprint reader, Intel4965n Card, Intel X3100 running Compiz-fusion, with sound working

Introduction

This document outlines configuring Ubuntu 7.10 (Gutsy Gibbon) on your Sony VGN Series. Most items will work out of the box and a base install should provide you with a completely working system. Due to the modular nature of the VGN series there are many different configuration, please read carefully and only make the changes specific to your system.

Installation Notes

• § If booting with the live CD gives you a blank screen you should select the “Safe Graphics” menu choice.

Display/Video

Accelerated Video and Desktop Effects

Intel 2D and 3D accelerated video work out of the box.

Due to | bug 111257, compiz is disabled on the Intel i965 based video cards. To fix it do a apt-get install compizconfig-settings-manager. On install add “SKIP_CHECKS=yes” to your “/etc/xdg/compiz/compiz-manager” .

Note: If you enable Compiz on an Intel card there will be issues with viewing media files, please see the bug report above for details

Intel X3100:

Plugging in an external monitor works, but is a clone of the built-in LCD by default. Using the Screens and Graphics tool located under Administration you can setup the second monitor as an extension of the existing screen or a clone for presentations.

Setting up dual monitors via the command line

If you like doing it via the command line and are using the Intel drivers you can use this example (Note all this should be possible using the Screens and Graphics tool so only make this change if you prefer the command line method):

This is an example for a 1680×1050 built-in LCD and a 1600×1200 external LCD: Add a “Virtual 3280 1200″ line in the Display SubSection of the Screen Section in your xorg.conf:

Exit to a virtual terminal (press: ctrl-alt-F1), login and type the following:

# sudo /etc/init.d/gdm stop

# xrandr –output LVDS –auto

To set the built-in LCD to ouput 1680×1050

# xrandr –output VGA –right-of LVDS

To extend the desktop

Fonts on High-Res Screens

On high-res screens (e.g. 15″ 1680×1050), some users consider the default fonts too be too large (Launchpad bug report). You can fix this by following these steps:

• 1. Open System->Preferences->Appearance
• 2. Select the “Fonts” tab
• 3. Click the “Details” button (lower right)
• 4. Adjust the Resolution down to 96dpi
• 5. Make sure you have Subpixel (LCD) Smoothing enabled
• 6. Save the preferences

If you also want small fonts on the GDM login window, you can do this:

• 1. Open System->Administration->Login Window
• 2. Select the ‘Security’ tab
• 3. Click the ‘Configure X-Server’ button
• 4. Append ‘-dpi 96′ (without quotes) to the text in the ‘Command’ field
• 5. Reboot the computer.

Brightness

Intel X3100:

The brightness controls should work out of the box on a fresh install.

Audio

Getting Sound to work

If you are using Intel ICH8(the newer sound chipsets) your sound might not work with a fresh install of Gutsy. To correct this simply make sure your backports repository is enabled in /etc/apt/source.list. Then run sudo apt-get install linux-backports-modules-generic . This will install the latest alsa drivers for your sound.

Fingerprint Reader

The reader works with ThinkFinger. General instructions available here and here. Instructions in French available at http://doc.ubuntu-fr.org/materiel/thinkfinger

Prebuilt packages are available from jldugger using Launchpad’s PPA:

Add the thinkfinger package repository by creating /etc/apt/sources.list.d/thinkfinger.list with these two lines:

deb http://ppa.launchpad.net/jldugger/ubuntu gutsy main restricted universe multiverse

deb-src http://ppa.launchpad.net/jldugger/ubuntu gutsy main restricted universe multiverse

Then update the package database and install packages:

$ sudo apt-get update

$ sudo apt-get install libpam-thinkfinger libthinkfinger-dev libthinkfinger-doc libthinkfinger0 thinkfinger-tools

After the package is installed add the following two lines to /etc/pam.d/common-auth

auth sufficient pam_thinkfinger.so

auth required pam_unix.so try_first_pass

Edit /etc/modules and add the following line:

uinput

Load the module manually for this session:

$ sudo modprobe uinput

Summary:

• § Recording fingerprints works
• § Login works
• § The password must be entered to unlock a locked screensaver
• § sudo works
• § gksu and gksudo hang: for example it is necessary to run synaptic twice and enter your password upon failure. To be able to use the Finger print reader in the session subsequently, kill the hanging gksu/gksudo process. A workaround is editing the Gnome System Menu (alacarte) to specify sudo instead of gksu/gksudo for the launching command and choose type “Application in Terminal”: this opens an extra terminal window for each superuser application you want to use though.

Please note: This post has been modified from the original post on http://www.thinkwiki.org/wiki/Installing_Ubuntu_7.10_(Gutsy_Gibbon)_on_a_ThinkPad_T61 to work for Sony Vaio Notebooks.

How to Configure MPLAB

MPLAB Setup

MPLAB is Microchips Integrated Development Environment. It can be download directly from Microchips MLAPB Site.

If you are using CCS‘ C-Compiler, make sure to run their MPLAB integration tool, otherwise the PIC Compiler will not work. The MPLAB integration tool for MPLAB version 6.xx will work for MPLAB v. 7.00.

After the installation you will find the highlighted tool suite (under Project select Set Language Tool Locations). Make sure to use this one. Do not use CCS C Compiler or you will get ‘BUILD FAILED’ after compiling and downloading the HEX file will not work.)

Before starting your own projects, make sure to configure MPLAB to not use a one-to-one-workspace setting. You can switch on this setting under Configure, Settings.

You also have to configure the configuration bits for the processor. The configuration can be done under Configure, Configuration Bits. See the following image (click on the image for a larger version) for the settings required for the Smart-Its or Particles.

After the workspaces and device parameters are set correctly, make a new workspace by using the Project Wizard (Project, Project Wizard). For Smart-Its programming, the chip is the PIC18F452, for Particle programming, the chip is the PIC18F6720.

Save you workspace now to prevent damage to your workspace because of MPLABs stability problems.

Now configure your programmer. We do use a MPLAB ICD2 (ICD = in circuit programmer) programmer. Select your programmer by clicking on Programmer, Select Programmer and then choosing your programmer.

Go to the menu Programmer and chose Settings.

Make sure to power the Particles from the MPLAB ICD2. When using Smart-Its, you need not to power the target chip.

Let the programmer automatically chose which memory ranges to write.

Now you can run the self test in the status tab.

Save your MPLAB workspace to make sure the programmer is selected when you open the workspace the next time.

MPLAB Programming

You can now add files to your project by right-clicking on Source Files in your Workspace (window with the title <muc.mcw>) and selecting Add Files… . In our example, we named the workspace muc.mcw and the project muc.mcp.

Click right on the <muc.mcp> and select Build Options. You now should add your own compile settings, e.g. additional include directories.

You can now click on the compile symbol and compile your source code. If your code contains any includes (e.g. for the PIC), these files are added automatically to the section Header Files in your project (here: muc.mcp). The output window there should read BUILD SUCCEEDED, preceded by warnings that may appear. Click on the image for a larger image.

Now you can program your device using the appropriate buttons of the MPLAB IDE. Click on the left icon (see image below) for downloading the code to the target

By clicking on the rising flank to start the program.

Programming HEX Files with MPLAB

To directly download hex files into a device, do the following:

• Close all open workspaces of MPLAB
• Configure your programmer
• In MPLAB, click on ‘File’ and select ‘Import’
• It seems that nothing is happening, but the hex file is imported
• Click on the programmer icon. The output window should state that the device is programmed

MPLAB Problems and Known Bugs

If you receive the error message ‘The format of the file XYZ.COD can not be read or written because its extension was not recognized‘ (see the picture below), then add ‘+DF’ to the compiler option string.

We only received this error on a Windows 2003 Server machine and could not reproduce it on any other operating system.

If you receive the error message ‘Warning! MPLAB IDE does not currently support this OS.’ on a Windows 2003 Machine, ignore it.

Attention: if you receive any warning or error message when compiling code with MPLAB, e.g. the message above on the .COD file, then the programming of the PICs with any programmer does not work! You will notice then that MPLAB does not write the programming region (0×00 – 0x…) in the output window and programming will be faster.

This tutorial was got from:

http://www.hcilab.org/resources/mplab/mplab-howto.htm

Introducing Prolog…

A.I is the heart and soul of many programs from games to military applications, artificial intelligence is involved. With its widespread applications one would expect there will be resources that try to encourage inquisitive minds but this is not the case, rather one will find that there is no standardized version of languages that are supposed to aid understand the concepts in A.I.

In this post, I will try to explain the things needed to help any user out there interested in learning programming in prolog how to go about. As I am no professional, but rather another struggling user there is a limit to my understanding of the language.

 

To code in prolog you will need the following:

1. A Prolog compiler: GNU Prolog by Daniel Diaz

2. A very good prolog book: Prolog Programming for Artificial Intelligence y Ivan Bratko

3. Lots of patience.

 

The compiler is very easy to setup, all you need to do is run the installer and it takes care of the rest for you. I initially started with Visual Prolog but discovered the IDE too hard to use and it is particularly difficult to understand for a beginning prolog programmer. On installing GNU Prolog compiler, you either write some code into a notepad then compile it directly to either ‘exe’ or ‘byte-code’. The exe is much faster but is machine dependent but the byte-code is slower and can be debugged. Note that the compiler is located in bin directory where your installation is so if you want to use it from console you will have to set your path variable. So far, I write code into a text editor then run the GNU Prolog console which is the actual interpreter. The prolog console can be told to consult your file in which the facts and rules have been clarified hence it answers any queries based on that rule set.

 

Recommended Resource for Prolog Programmers:

• Gprolog Manual

• http://www.coli.uni-saarland.de/~kris/learn-prolog-now/html/toc.html

• Prolog Programming for A.I by Ivan Bratko

 

Thanks for reading my blog.

…Building a simple maze solver(Beginnings of AM’TER)

Building a simple Robot Part 1

This tutorial is divided into 3 parts

1.       Summary of Parts needed for a functional Robots

2.       Configurations  of both Hardware and Software

3.       Programming the Robot

The main purpose of this tutorial is to aid other people who might have difficulties designing a simple robot such as a maze solving robot. I will formally introduce a few of the basic concepts by first explain how to make a simple LED blinker. Hereafter I will discuss how an autonomous maze explorer can be built.

When I built my first robot one of the main challenges I had to overcome was how to make sense of the various tutorial available online. Most of the tutorials out there only covered a section of the challenges a beginner Roboticist might have. This is not only inadequate but can also be very confusing for many aspiring Roboticists out there.

Hardware Needed:

1.       A Microprocessor

2.       Some Circuit Board

3.       Power Supply

4.       A Multimeter

5.       A Chip Programmer

Software Needed:

1.       Some IDE Interface

2.       Compiler

We will start out by examining the hardware needed in basic details

Microprocessor: Microchip’s Pic series is a good micro processor that can be used for making robots. It has a very active forum which I discovered was a great resource when initially starting out with robots. In this case, I would recommend the Pic 18F876A micro controller. It is a 28 pin chip with 5 A/D channels and a whole range of features.

Circuit Board: Before one can successfully implement a design of a circuit board, he/she must have an underlying knowledge of the fundamentals components of an electrical circuitry. I did not have this background when build my own robot hence, I opted for an already built circuit board. There are numerous board available depending on the task/nature of the robot that is to be designed. I recommend microcontrollershop’s  OLimex boards (http://microcontrollershop.com/product_info.php?cPath=112_160_197&products_id=1849)

Power Supply: Before the robot can be fully autonomous it needs an independent source of power supply. We shall not concern ourselves with this right now rather go for the generic universal power supply which can also be got from the microcontroller shop.

Multimeter: A multimeter essentially allows you to measure voltage, current, resistance amongst other measurable quantities. They are inexpensive and can be a very useful tool in debugging you circuit. You can easily get one of these at any Radioshack store.

Programmer: There are several kinds of programmers that can be used to “burn” your code to the pic chip. There are general purpose programmers like the JDM Programmer and also special purpose programmers like the MPLAB ICD2 (In-Circuit Debugging). I recommend MPLAB ICD2 simply because it is widely used and has a very active support forum.

In the case of the software needed to successfully write your code and communicate with the pic chip, there are several options. One can use the MPLAB IDE which of course integrates with the MPLAB ICD2 flawlessly, or your code can also be written in a simple text editor and 3^rd party code burning tools can be used to transfer the code that has been compiled to the chip. Please note that the MPLAB IDE does not come with a compiler, in order to use a compiler you will have to purchase one (I use CCS C Compiler). There are also open source versions available for use.

Configuring ssh & ftp in OpenBSD for speed and security.

 

OpenBSD as we all know is secure by default. This much acclaimed operating system is known for its proven approach to security with only two (2) remote holes in over ten years. I will attempt to explain how to configure and setup OpenBSD to run as an ssh and ftp server keeping the key elements of speed and security in mind.

After the initial install of OpenBSD no ports system will be installed. Installing the ports system differs from server to server but largely depends on the installation media. If the operating system was installed from a media such as a cd that was “bought” not downloaded for free it usually contains the appropriate port matching your system specifications; mount your CD and navigate to the directory containing the package “ports.tar.gz”  and perform the following steps:

        I.            Copy the files from the CD to a temp directory with the command:  

·         cp /my/installation/media /tmp

     2.       Navigate to the location for your ports system

·         # cd  /usr/

     3.       Un-tar the files

·         # tar  xvzf /tmp/ports.tar.gz

When the files are un-tarred you should have a functional ports system.  Alternatively if the files are available as selectable packages during installation, you can select it and let the OpenBSD installer perform all the necessary steps to make them usable.

If you performed an installation from a snapshot CD then navigate to the website where you downloaded the images from and in the snapshots folder you will usually find the required package ports.tar.gz. Download this file with the command

·         # wget ftp://path /to/my/installation/source/ports.tar.gz

Since wget downloads to the current directory take note of the directory you are in; downloading to /tmp should be appropriate.

By this time you should have a properly configured ports system. Navigating to the directory “/usr/ports/” should show you all the packages that can be installed in the system. Now to install the appropriate ftp server:

·         # cd /usr/ports/net/     ##navigating to the “net” folder

·         # make install clean pure-ftpd     ##automatically installing ftp server with all dependencies

·         # pkg_info    ##lists all the installed packages, pure-ftpd should be there

·         # reboot     ##rebooting the computer

·         #kill –HUP `cat /var/run/pure-ftpd.pid` ## to restart the dameon without rebooting

On reboot, your ftp should be properly setup to use the user accounts present on the system. Additional installation options such as enabling the use of an sql database to store user account and changing root directory options can be found at the pure-ftp website.

 

The ssh on the other hand is much simpler to install. To avoid all the hassles you can simply answer yes to the question that asks you to enable sshd during installation. The configuration file for the sshd can edited by:

·         #vi /etc/ssh/sshd_conf   ##editing the ssh dameon configuration file

 

Please don’t edit  the file unless it is absolutely necessary. The sshd comes secure by default and editing this file may introduce bugs/exploits if caution is not taken.

 

To start the sshd service simply edit the file rc.conf

·         #vi  /etc/rc.conf #replace the No on sshd_flags to “”

 

More commands to use for package management include the following:

-          make search key=”package you are looking for”

-          pkg_delete

-          pkg_add

-          make search name=”name of package”

-          make update

-          make install clean

-          make clean=depends

-          make uninstall

-          make reinstall

-          pkg_info

Configuring Xen on Ubuntu Feisty

With the advent of Supercomputers and the need for highly scalable and reliable systems, Xen was formed. Xen can be considered to be a superior but esoteric attempt at Virtualization than VMWare ever was. This blog post seeks to educate immature and inexperienced greenhorns like myself on the easiest and possibly least efficient(less hassles involved) way of setting up Xen on a machine running Ubuntu 7.0(Fiesty).
Our boot loader(the program that loads up the operating system) must be a grub boot loader.

We must ensure that our processor supports virtualization. Virtualization can be of 2 types:
1. Para Virtualized Guest Systems
2. Fully Virtualized Guest Systems

For Para Virtualized Guests, the Intel processor must have the PAE extension and as for AMD x86_64 & ia64 processors support this mode of virtualization.

##################################################

$ grep pae /proc/cpuinfo
flags :fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow up ts

##################################################

For Fully Virtualized Guests, the Intel processor must have the VMX flag or in the case of AMD SVM flag.

Once we determine our processor supports some form of virtualisation, we can then get into the nitty gritty of virtualization…;-)

1. Ensure our universal repository is enabled.
#################################################
sudo vi /etc/apt/sources.list
#################################################

2. Update all our repositories
#################################################
sudo apt-get update
#################################################

3. Install Xen from the Ubuntu repository
#################################################
sudo apt-get install ubuntu-xen-server
#################################################

4. Reboot the Ubuntu Machine and on startup boot into the Xen Kernel

5. Ensure that the host machine(Domain-0) is running
#################################################
sudo xm list
#################################################

6. Edit our Xen configuration file:
#################################################
sudo vi /etc/xen/xend-config.sxp
#################################################

7. Uncomment out this line:

(network-script network-bridge)

8. Comment out the following line:

(network-script network-dummy)

9. Restart xend
################################################
sudo xend restart
################################################

10. Create two Xen images -A virtual OS image and its associated swap file- using the disk dump utility and place in any directory of choice(mine is xen_images)
#######################################################
dd if=/dev/zero of=/xen-images/fedora_base.img bs=1024k count=2000
dd if=/dev/zero of=/xen-images/fedora_base_swap.img bs=1024k count=500
#######################################################

11. Format both images to their different file systems
###############################################
mkfs.ext3 /xen-images/fedora_base.img
mkswap /xen-images/fedora_base_swap.img
###############################################

12. Changing permissions on the images to ensure their integrity and prevent unauthorized tampering.
###############################################
chmod 640 /xen-images/fedora_base*
###############################################

13. We create a mount directory where our image will be mounted for an installation of any operating system of choice.
###############################################
mkdir /xen-images/mnt
###############################################

14. We can then mount the image
###############################################
mount -o loop /xen-images/fedora_base.img /xen-images/mnt
###############################################

to be cont’d