Run Levels in Linux Operating system

Linux utilizes what is called "runlevels". A runlevel is a software configuration of the system that allows only a selected group of processes to exist. Init can run the system in one of eight runlevels. These runlevels are 0-6 and S or s. The system runs in only one of these runlevels at a time. Typically these runlevels are used for different purposes. Runlevels 0, 1, and 6 are reserved. For Redhat Linux version 6, the runlevels are:

0		-		halt
1		-		Single user mode
2		-		Multiuser, without NFS (The same as 3, if you don't have networking)
3		-		Full multiuser mode
4		-		unused
5		-		X11
6		-		Reboot

1.      level 0 : to halt the system, it reboots the systems again and again after login in

2.      level1 :single user mode, this is a special mode in which only one use ie the super user mode in which limited system based linux commands work.

3.      level2-level5 : this is the multi user mode in which the system works at its full potential with all the command set that it supports

4.      level 6 : entering into this level reboots the system.

How to change root password with out login in

This could be easily done using single user mode of linux.

1.To boot into single user mode change any entry of grub that boots ubuntu
2. Go to the kernel line and add single at the end of it.
3. Now boot from it.
4. Once it boots to change root password
Passwd root
5. Change password and enjoy

simple way to install ubuntu 11.04

First of all ensure u have at least 20 GB of space free in ur hardisk(free means unallocated memory)

Once u do that reboot ur system and boot the ubuntu cd from the boot option or change boot preferences from the BIOS.

Once your BIOS is configured to boot from CD first, if you have Ubuntu in the drive, you should see the splash screen with a ubuntu written on it. Ubuntu will take a couple of minutes to load up. Just be patient.

Select your preferred language.
If you have at least 512 MB of RAM, you may want to select Try Ubuntu, as it will allow you to do other things (check your email, browse the web) while you're installing Ubuntu.
If you have only 256 MB or 384 MB of RAM, you should select Install Ubuntu. This will give you the same installation screens you see below, but you won't have the rest of the Ubuntu live session running as well.
Select your language.
There is a new option in the Ubuntu 11.04 and 10.10 installers that asks if you want to install closed source third-party software for MP3 playback and Flash, for example. I would strongly suggest—unless you know who Richard Stallman is—that you check (or tick) this option.
If you want to install Ubuntu next to Windows so you can choose which operating system you want at boot-up, select the first option. As mentioned before, do this only if you don't anticipate even a small possiblity of returning exclusively to Windows. A traditional dual-boot can be undone but it's not easy.
This is how u do it go to advanced option
Now make four partitions out of 20 gb free partition(if u have free space in extended partition choose partition type as logical)
One for boot with
Mount point as /boot
Filetype as Ext3
And size 300 MB
Next for root (where all system files are stored)
Mount point as /
Filetype as Ext3
And size 7 GB
Then for home directory( where ur main data is stored)
Mount point /home
Filetype Ext3
And size 9GB
Then for swap(ie for memory requirements)
No mount point
File type swap
Size 4 GB
While Ubuntu is preparing files to copy over for installation, it'll ask you some questions. They're self-explanatory.
Eventually, the installation will finish (the whole thing can take anywhere between 15 minutes and an hour, depending on the speed of your computer). You can either Continue Testing if you want to shutdown your computer or Restart Now if you want to restart your computer.
Either way, Ubuntu will eject your CD (or prompt you for when to remove your USB stick, if you used UNetBootIn instead of a CD burning program). The next time you boot up, you should have a working Ubuntu installation!

Share Ur Ubuntu Desktop using Remote desktop using VNC

Remote Desktop will only work if there’s a GNOME login session.Leaving your computer with an unattended GNOME login session is not secure and not recommended.
Some Tips
1) You can lock your screen using System--->Quit

Once you click on quit you should see the following screen here you need to select lockscreen

2) switch off your monitor when computer is left unattended
Configuring Remote Desktop
First you need to go to System -> Preferences -> Remote Desktop

Once it opens you should see the following screen

In the above screen you need to configure remote desktop preferences for sharing and security
For Sharing
you need to tick the box next to the following two options
Allow other users to view your desktop
Allow other users to control your desktop
For Security
you need to tick the box next to the following two options
Ask you for confirmation (If you tick this option some one need to click on allow from remote desktop once it connected if you don’t want you can untick this option)
Require the user to enter this password:
Password: Specify the password

Connecting from Ubuntu Machine
Open your terminal from Applications--->Accessories--->Terminal and enter the following command
vncviewer -fullscreen 192.168.2.23:0
now you should see the following message asking for password enter the password after complete success you can see VNC authentication succeeded message and starting remote desktop
VNC viewer version 3.3.7 - built Jul 4 2006 10:04:48
Copyright (C) 2002-2003 RealVNC Ltd.
Copyright (C) 1994-2000 AT&T Laboratories Cambridge.
See http://www.realvnc.com for information on VNC.
VNC server supports protocol version 3.7 (viewer 3.3)
Password:
VNC authentication succeeded
If you want to quit vncviewer
Press ‘F8′ and select Quit viewer
Connecting from Windows machine
If you are trying to connect from your windows machine you need to install vncviewer of your choice i have installed from here http://www.realvnc.com/download.html.Install this program once you install this you can opem from start--->All programs--->RealVNC--->VNC Viewer 4--->Run VNC Viewer once it opens you should see the following screen here enter the remotemachine ipaddress:0 format and click ok

Now it will prompt for password enter your password and click ok

Now on the remote machine you should see the following screen asking for permission to allow this connection you need to click on allow this will comeup only if you tick “Ask you for confirmation” option under sharing

Once it connected you should see the remote machine desktop.

Scalable Images in Linux

Scalable Vector Graphics (SVG) is a family of specifications of an XML-based file format for describing two-dimensional vector graphics, both static and dynamic (i.e. interactive or animated).

The SVG specification is an open standard that has been under development by the World Wide Web Consortium (W3C) since 1999.

SVG images and their behaviors are defined in XML text files. This means that they can be searched, indexed, scripted and, if required, compressed. Since they are XML files, SVG images can be created and edited with any text editor, but drawing programs are also available that support SVG file formats.

All major modern web browsers have at least some degree of support and render SVG markup directly with the exception of any version of Microsoft Internet Explorer (IE) released for the widely used Windows XP.

SVG allows three types of graphic objects: vector graphics, raster graphics, and text. Graphical objects, including PNG and JPEG raster images, can be grouped, styled, transformed, and composited into previously rendered objects. SVG does not directly support z-indices[6] that separate drawing order from document order for overlapping objects, unlike some other vector markup languages like VML. Text can be in any XML namespace suitable to the application, which enhances search ability and accessibility of the SVG graphics. The feature set includes nested transformations, clipping paths, alpha masks, filter effects, template objects and extensibility.

Printing

Though the SVG Specification primarily focuses on vector graphics markup language, its design includes the basic capabilities of a page description language (PDL), like Adobe's PDF. It contains provisions for rich graphics, and is also compatible with CSS for styling purposes. It is unlike XHTML, whose primary purpose is communication of content, not presentation, and therefore specifies objects to be displayed but not where to place such objects. Conversely SVG is an ideal PDL for print-oriented uses, as it contains all the functionality required to place each glyph and image in a chosen location on the final page.

Compression

SVG images, being XML, contain many repeated fragments of text and are thus particularly suited to compression by gzip, though other compression methods may be used effectively. Once an SVG image has been compressed it may be referred to as an "SVGZ" image, with the corresponding filename extension. The resulting file may be as small as 20% of the original size.

Use in Linux

Most images in icon set in themes in gnome and graphics user interfaces uses these scalable images for dynamic imaging displays and thus the use and manupulation of such images could be very vital in development of themes and icon set.The most popular editor for svg images is Inkscape which is able to perform all kinds of editing in a scalable image.

Basic Files Systems in Linux

minix

is the filesystem used in the Minix operating system, the first to run under Linux. It has a number of shortcomings: a 64MB partition size limit, short filenames, a single time stamp, etc. It remains useful for floppies and RAM disks.

ext

is an elaborate extension of the minix filesystem. It has been completely superseded by the second version of the extended filesystem (ext2) and has been removed from the kernel (in 2.1.21).

ext2

is the high performance disk filesystem used by Linux for fixed disks as well as removable media. The second extended filesystem was designed as an extension of the extended file system (ext). ext2 offers the best performance (in terms of speed and CPU usage) of the filesystems supported under Linux.

ext3

is a journaling version of the ext2 filesystem. It is easy to switch back and forth between ext2 and ext3.

xiafs

was designed and implemented to be a stable, safe filesystem by extending the Minix filesystem code. It provides the basic most requested features without undue complexity. The xia filesystem is no longer actively developed or maintained. It was removed from the kernel in 2.1.21.

msdos

is the filesystem used by DOS, Windows, and some OS/2 computers. msdos filenames can be no longer than 8 characters, followed by an optional period and 3 character extension.

umsdos

is an extended DOS filesystem used by Linux. It adds capability for long filenames, UID/GID, POSIX permissions, and special files (devices, named pipes, etc.) under the DOS filesystem, without sacrificing compatibility with DOS.

vfat

is an extended DOS filesystem used by Microsoft Windows95 and Windows NT. VFAT adds the capability to use long filenames under the MSDOS filesystem.

proc

is a pseudo-filesystem which is used as an interface to kernel data structures rather than reading and interpreting /dev/kmem. In particular, its files do not take disk space. See proc(5).

iso9660

is a CD-ROM filesystem type conforming to the ISO 9660 standard.

High Sierra

Linux supports High Sierra, the precursor to the ISO 9660 standard for CD-ROM filesystems. It is automatically recognized within the iso9660 filesystem support under Linux.

Rock Ridge

Linux also supports the System Use Sharing Protocol records specified by the Rock Ridge Interchange Protocol. They are used to further describe the files in the iso9660 filesystem to a UNIX host, and provide information such as long filenames, UID/GID, POSIX permissions, and devices. It is automatically recognized within the iso9660 filesystem support under Linux.

hpfs

is the High Performance Filesystem, used in OS/2. This filesystem is read-only under Linux due to the lack of available documentation.

sysv

is an implementation of the SystemV/Coherent filesystem for Linux. It implements all of Xenix FS, SystemV/386 FS, and Coherent FS.

nfs

is the network filesystem used to access disks located on remote computers.

smb

is a network filesystem that supports the SMB protocol, used by Windows for Workgroups, Windows NT, and Lan Manager. To use smb fs, you need a special mount program, which can be found in the ksmbfs package, found at ftp://sunsite.unc.edu/pub/Linux/system/Filesystems/smbfs.

ncpfs

is a network filesystem that supports the NCP protocol, used by Novell NetWare. To use ncpfs, you need special programs, which can be found at ftp://linux01.gwdg.de/pub/ncpfs.