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Tuesday, 5 July 2011

Linux or GNU/Linux ?

You've probably noticed that Linux as an operating system is referred to in some cases as "Linux" and in others as "GNU/Linux." The reason behind this is that Linux is the kernel of an operating system. The wide range of applications that make the operating system useful are the GNU software. For example, the windowing system, compiler, variety of shells, development tools, editors, utilities, and other applications exist outside of the kernel, many of which are GNU software. For this reason, many consider "GNU/Linux" a more appropriate name for the operating system, while "Linux" is appropriate when referring to just the kernel.

Do you Know what Android is ?

Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language.

Features

Application framework enabling reuse and replacement of components
Dalvik virtual machine optimized for mobile devices
Integrated browser based on the open source WebKit engine
Optimized graphics powered by a custom 2D graphics library; 3D graphics based on the OpenGL ES 1.0 specification (hardware acceleration optional)
SQLite for structured data storage
Media support for common audio, video, and still image formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, GIF)
GSM Telephony (hardware dependent)
Bluetooth, EDGE, 3G, and WiFi (hardware dependent)
Camera, GPS, compass, and accelerometer (hardware dependent)
Rich development environment including a device emulator, tools for debugging, memory and performance profiling, and a plugin for the Eclipse IDE

Android Architecture

The following diagram shows the major components of the Android operating system. Each section is described in more detail below.

Applications

Android will ship with a set of core applications including an email client, SMS program, calendar, maps, browser, contacts, and others. All applications are written using the Java programming language.

Application Framework

By providing an open development platform, Android offers developers the ability to build extremely rich and innovative applications. Developers are free to take advantage of the device hardware, access location information, run background services, set alarms, add notifications to the status bar, and much, much more.

Developers have full access to the same framework APIs used by the core applications. The application architecture is designed to simplify the reuse of components; any application can publish its capabilities and any other application may then make use of those capabilities (subject to security constraints enforced by the framework). This same mechanism allows components to be replaced by the user.

Underlying all applications is a set of services and systems, including:

A rich and extensible set of Views that can be used to build an application, including lists, grids, text boxes, buttons, and even an embeddable web browser
Content Providers that enable applications to access data from other applications (such as Contacts), or to share their own data
A Resource Manager, providing access to non-code resources such as localized strings, graphics, and layout files
A Notification Manager that enables all applications to display custom alerts in the status bar
An Activity Manager that manages the lifecycle of applications and provides a common navigation backstack

For more details and a walkthrough of an application, see the Notepad Tutorial.

Libraries

Android includes a set of C/C++ libraries used by various components of the Android system. These capabilities are exposed to developers through the Android application framework. Some of the core libraries are listed below:

System C library - a BSD-derived implementation of the standard C system library (libc), tuned for embedded Linux-based devices
Media Libraries - based on PacketVideo's OpenCORE; the libraries support playback and recording of many popular audio and video formats, as well as static image files, including MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG
Surface Manager - manages access to the display subsystem and seamlessly composites 2D and 3D graphic layers from multiple applications
LibWebCore - a modern web browser engine which powers both the Android browser and an embeddable web view
SGL - the underlying 2D graphics engine
3D libraries - an implementation based on OpenGL ES 1.0 APIs; the libraries use either hardware 3D acceleration (where available) or the included, highly optimized 3D software rasterizer
FreeType - bitmap and vector font rendering
SQLite - a powerful and lightweight relational database engine available to all applications

Android Runtime

Android includes a set of core libraries that provides most of the functionality available in the core libraries of the Java programming language.

Every Android application runs in its own process, with its own instance of the Dalvik virtual machine. Dalvik has been written so that a device can run multiple VMs efficiently. The Dalvik VM executes files in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.

The Dalvik VM relies on the Linux kernel for underlying functionality such as threading and low-level memory management.

Linux Kernel

Android relies on Linux version 2.6 for core system services such as security, memory management, process management, network stack, and driver model. The kernel also acts as an abstraction layer between the hardware and the rest of the software stack.

compare Linux and UNIX

What is the difference between Linux and UNIX operating systems?

UNIX is copyrighted name only big companies are allowed to use the UNIX copyright and name, so IBM AIX and Sun Solaris and HP-UX all are UNIX operating systems. The Open Group holds the UNIX trademark in trust for the industry, and manages the UNIX trademark licensing program.

Most UNIX systems are commercial in nature.

Linux is a UNIX Clone

But if you consider Portable Operating System Interface (POSIX) standards then Linux can be considered as UNIX. To quote from Official Linux kernel README file:

Linux is a Unix clone written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX compliance.

However, "Open Group" do not approve of the construction "Unix-like", and consider it misuse of their UNIX trademark.

Linux Is Just a Kernel

Linux is just a kernel. All Linux distributions includes GUI system + GNU utilities (such as cp, mv, ls,date, bash etc) + installation & management tools + GNU c/c++ Compilers + Editors (vi) + and various applications (such as OpenOffice, Firefox). However, most UNIX operating systems are considered as a complete operating system as everything come from a single source or vendor.

As I said earlier Linux is just a kernel and Linux distribution makes it complete usable operating systems by adding various applications. Most UNIX operating systems comes with A-Z programs such as editor, compilers etc. For example HP-UX or Solaris comes with A-Z programs.

License and cost

Linux is Free (as in beer [freedom]). You can download it from the Internet or redistribute it under GNU licenses. You will see the best community support for Linux. Most UNIX like operating systems are not free (but this is changing fast, for example OpenSolaris UNIX). However, some Linux distributions such as Redhat / Novell provides additional Linux support, consultancy, bug fixing, and training for additional fees.

User-Friendly

Linux is considered as most user friendly UNIX like operating systems. It makes it easy to install sound card, flash players, and other desktop goodies. However, Apple OS X is most popular UNIX operating system for desktop usage.

Security Firewall Software

Linux comes with open source netfilter/iptables based firewall tool to protect your server and desktop from the crackers and hackers. UNIX operating systems comes with its own firewall product (for example Solaris UNIX comes with ipfilter based firewall) or you need to purchase a 3rd party software such as Checkpoint UNIX firewall.

Backup and Recovery Software

UNIX and Linux comes with different set of tools for backing up data to tape and other backup media. However, both of them share some common tools such as tar, dump/restore, and cpio etc.

File Systems

Linux by default supports and use ext3 or ext4 file systems.
UNIX comes with various file systems such as jfs, gpfs (AIX), jfs, gpfs (HP-UX), jfs, gpfs (Solaris).

System Administration Tools

UNIX comes with its own tools such as SAM on HP-UX.
Suse Linux comes with Yast
Redhat Linux comes with its own gui tools called redhat-config-*.

However, editing text config file and typing commands are most popular options for sys admin work under UNIX and Linux.

System Startup Scripts

Almost every version of UNIX and Linux comes with system initialization script but they are located in different directories:

HP-UX - /sbin/init.d
AIX - /etc/rc.d/init.d
Linux - /etc/init.d

End User Perspective

The differences are not that big for the average end user. They will use the same shell (e.g. bash or ksh) and other development tools such as Perl or Eclipse development tool.

System Administrator Perspective

Again, the differences are not that big for the system administrator. However, you may notice various differences while performing the following operations:

Software installation procedure
Hardware device names
Various admin commands or utilities
Software RAID devices and mirroring
Logical volume management
Package management
Patch management

UNIX Operating System Names

A few popular names:

HP-UX
IBM AIX
Sun Solairs
Mac OS X
IRIX

Linux Distribution (Operating System) Names

A few popular names:

Redhat Enterprise Linux
Fedora Linux
Debian Linux
Suse Enterprise Linux
Ubuntu Linux

Common Things Between Linux & UNIX

Both share many common applications such as:

GUI, file, and windows managers (KDE, Gnome)
Shells (ksh, csh, bash)
Various office applications such as OpenOffice.org
Development tools (perl, php, python, GNU c/c++ compilers)
Posix interface

A Sample UNIX Desktop Screenshot

Fig.01: UNIX Desktop - IRIX 6.5 Desktop

A Sample Linux Desktop Screenshot

Fig.02: Linux KDE desktop environment

UNIX and Linux Hardware

Commercial UNIX hardware has more advanced initial boot options such as:

Decide how to boot
Check system health
Set hardware parameters etc

The BIOS that is standard in PCs which is used by Linux has few, of these features. UNIX hardware or servers are pretty expensive as compare to Linux server systems.

New Fedora 15's five best features

Fedora Linux not for everyone. If you’re an experienced Linux user who wants an easy-to-use desktop Linux, I recommend Mint 11. If you’re new to Linux and just want something that’s easy to pick up and use, I think you shouldgive Ubuntu 11.04 a try. But, if you’re a Linux expert, and want to explore the outer limits of what’s possible with Linux, then Red Hat’s new Fedora 15 Linux is the distribution for you.

Why? Well, here are my five favorite reasons to use Fedora 15. I’m going to start though with one reason I don’t care for this release of Fedora. Let’s call this one: Feature 0.

The GNOME 3 desktop environment

GNOME 3 claims to be the “the next generation of GNOME with a brand new user interface. It provides a completely new and modern desktop that has been designed for today’s users and technologies.” It’s not.

First, did we really need a “completely new desktop?” I don’t think so. I quite liked GNOME the 2.x series. It worked well for me and I didn’t need to learn anything new to use it. I get the point of Ubuntu’s Unity, which is a radically different shell that rides on top of GNOME. Unity is meant for Windows and Mac users who’ve never used Linux It’s also clearly designed to eventually become a tablet interface. When I look at GNOME though what I see is change just for the sake of change not change for greater end-user usability.

The idea of GNOME 3 was to get rid of clutter OK, I can see that, but in doing it GNOME’s designers had made GNOME less usable For example, in shifting from one project to another in your workspace you need to use the dashboard as a window management interface For me, this is like having to stop my car to shift gears That by itself is so annoying that I quickly stopped using GNOME 3.0.

I also found miss each windows’ minimize and maximize buttons. You can still minimize and maximize application windows, but what used to be an automatic action now wastes time. Finally, GNOME makes it very hard indeed to tweak your desktop. There’s no easy way to even set up a screen saver! I mean seriously, I have to do something like:

gsettings set org.gnome.desktop.interface gtk-theme 'Clearlooks‘

from a shell just to change my desktop theme?

GNOME 3 Failure: I saw this message far too many times.

It also doesn’t help any that GNOME 3 won’t run on basic graphics hardware. You need just the right mix of graphics and graphic drivers to get it to work. On my systems, I was only able to get one to work by using the Radeon driver for an older ATI graphics card.

In short, GNOME 3.0 is new but for users it’s a step backward. Fedora 15 is the first major distribution to include GNOME 3 by default. That was a mistake. Like Fedora 4 in its first not ready for prime time versions, GNOME 3 is not what most users want from a desktop. As for me, I’m sticking with GNOME 2.32, with occasional visits to KDE 4.6.

Now that I’ve got that out of my system, here’s what I like about Fedora 15.

5 Good Things about Fedora 15

1) Better power management

Desktop Linux has never done a great job of laptop battery management. Fortunately, Linux doesn’t drink up that much power so it usually ends up with decent battery life anyway. But, Fedora 15 redesigned power management utilities give it better battery life than other Linuxes.

I checked this by running Intec Battery Mark 1.1 on Windows XP in aVirtualBox virtual machine on my Lenovo ThinkPad R61 with its 2.2GHz Intel Core 2 Duo processor T7500 and 2GBs of RAM. With Mint 11, my six-cell battery lasted an hour and fifty-seven minutes. That’s pretty darn good for a three-year old battery.

With Fedora 15, though, it made it to 2 hours and ten minutes, which is pretty darn close to what it used to do when it was brand new. Anything that gives me 10% better battery life is a major win in my book.

2) Better End-User Software

Like most up-to-the-minute Linux distributions, Fedora uses LibreOfficein place of OpenOffice, as its office suite. LibreOffice, while an OpenOffice fork is better thought of as an improved version of OpenOffice. It looks the same, works the same, but it’s also faster, has many minor bug fixes and has far better Microsoft Office file format compatibility. Last, but not least, since Oracle will no longer be putting any resources into OpenOffice, LibreOffice is the most significant open-source office suite yet that’s still being actively developed.

Firefox 4 in Fedora 15 worked just fine.

In addition, Fedora includes Firefox 4, which is certainly better than the older Firefox 3.x series. On the other hand, I would have been happier if it had used Chrome 11. But, no worries, this is Linux. Installing Chrome and making it my default browser took me less time to do than it did to write this paragraph.

3) Dynamic Firewall

OK, this is a beta feature so you have to manually install it and only network administrators are likely to find it that exciting, but I–who sometimes still wears his network administrator hat–think that it has great potential.

Like its name suggest dynamic firewall enables you to change firewall settings without needing to restart the firewall. So, for example, you can set the firewall to change its rules, as needed for virtual machines or Virtual Private Networks (VPN).

You can also use it to open up the firewall for a specific network request, such as discovering a local printer or a Windows server, and then closing down the port once you’re done with that procedure. This has got real possibilities and I like it already. If all goes well, it will become the default firewall in Fedora 16 and eventually in Red Hat Enterprise Linux (RHEL)

4) Virtual Desktop Support

Slowly, but surely, Simple Protocol for Independent Computing Environments (SPICE)virtual desktops are coming to Red Hat. In Fedora 15, SPICE has been integrated into the virtualization manager, virt-manager.

Since Red Hat future desktops plans center on virtual desktops,presumably running on Kernel Virtual Machine (KVM), I find this very interesting. I also found that you can finally set up speedy SPICE virtual desktops without tweaking configuration files by hand.

5) RPM 4.9.0 Package Manager

RPM 4.9.0, Fedora and RHEL’s software manager has been given a real tune-up. It’s now easier than ever to install software on Fedora .For more on that see the RPM 4.9.0 release notes. The bottom line is that RPM does a much better job of handling any RPM package that you try to install on your system.

There are many other neat features as well such as security improvements in handling common Security Enhanced Linux (SELinux)problems with an easy to use GUI and improved encrypted home directory support. And then there’s the BoxGringer image and virtual machine (VM) creator, and, at long, long last, a built-in consistent and sane network device naming system.

Now if they would only do something with GNOME 3! Or, better still, the GNOME 3 designers brought back some of its more end-user friendly bits and bites I’d be perfectly happy with Fedora.