Now you can run Linux on your web browser. You don’t need those freaky dual boot systems or any virtual machine to run Linux on your system. All you have to do is having latest version of Chrome, Firefox or Internet Explorer browser. Open a website made by a geek Fabrice Bellard, which allows you to run almost all the crucial commands you can use in Linux. The best part is, you can open and use the website on your iPad too.


This emulator is one of the finest example of the power of Java script. The application runs all the crucial commands like pwd, cd, ls, cp, rm, mv, mkdir, rmdir, vi, cat, touch etc. While trying the app, I found that it lacks some of the advanced commands cron job command, daemon processes, init and many other advanced commands. But for beginner Linux users, it will be a great fun.

There are following devices in this emulator:
32 bit x86 compatible CPU
8259 Programmable Interrupt Controller
8254 Programmable Interrupt Timer
16450 UART
Real Time Clock.

This emulator is supported by following browsers
Firefox 4.x
Chrome 11
Opera 11.11
Internet Explorer 9

Try out Linux Emulator at http://bellard.org/jslinux/


All Linux Fanatics Enjoy !!

1) Don't attach, embed

By default, Gmail gives you the option of only attaching images to an email. However, with this feature enabled you can embed images from your computer or from a website directly into the mail body. Go to Settings, click on Labs, scroll down to the feature that says "Inserting Images" and enable it. You will notice the new insert image box in your mail composer right next to the emoticon icon.

2) Stop that mail

Pressed the send mail button too quickly? Gmail Labs has a feature that gives you a few seconds to stop the mail from going out after you press the send button. Go to Settings, click on Labs and enable the option that says "Undo Send".

Click General under Settings and here you can select the time (up to 30 seconds) for which the email can be stopped after it is sent. When you press the send button and the inbox comes up, you would see a yellow box saying, "Your message has been sent. Undo or View message" on top. Click on undo to cancel sending the mail and get the draft back. You can then make the necessary changes to the text or add the recipients you forgot and send again.

3) Sharing your power

This feature is useful for people who have multiple Gmail address or who want to grant read/write permission for their account to another user. Go to Settings, click on Accounts and Import, at the bottom you will see an option that says "Grant Access to your account".

Click on Add Account and enter the Gmail address of the person you want to grant access. Once the person accepts the verification mail, he/she can access your account by clicking on the arrow next to his own mail ID on top right and selecting your mail ID. The access allows the user to read, write and delete mails.

4) Reply to all

Gmail's default reply button composes the mail to the person who has sent the mail ignoring all the people who were put in CC. If you have to do a reply all, you have to press the arrow next to the reply box and then select "reply to all".

Instead, you can set the "reply to all" function as default. Go to Settings, click on Labs and enable "Default reply to all" feature. It is far simpler to just remove selective email IDs from the CC box than selecting " reply to all" from a drop down box every time.

5) My Time, Not Your Time

While communicating with friends, family or colleagues in different parts of the world, we sometimes forget about time zones. While it is mid-afternoon for you, it might be midnight for the recipient and hence an immediate reply will not come.

To know the difference in time zones for both parties, enable the "Sender Time Zone" feature by going to Settings and clicking on Labs. Now, when you click on "show details" in the mail, you can see the time at which you have sent the mail and what time is at the receiver's end and vice versa.

6) Peek-a-boo

Sometimes, you want to just have a quick look at the mail without opening the whole conversation. Gmail Labs enables you to do this with a simple tweak. Go to Settings, click on Labs and enable the "Message Sneak Peak" feature. Now, when you right click on any mail from the inbox, it will show you the latest mail received or sent in the conversation along with options to delete or mark as read, you don't have to open the entire conversation.

7) Control the content

You've probably noticed those little one, line ads that keep rotating on the top of the inbox above the various buttons. Not only are they unobtrusive, but also they can be rather helpful, sometimes offering relevant information.

Those ads are called Web-Clips and Gmail gives you the option to select what kind of content you want to see there. Go to Settings, click on Web-Clips and here you can remove all the topics that Gmail has added by default. Instead add the topics that you want to read about from the available selection. You can also add the RSS feed of your favorite website by entering it in the search box on the left and adding the feed.

8) Next in line

While checking your mail or going through results of searched mail, when you delete or achieve a conversation, Gmail takes you back to the inbox or search results listing. Wouldn't it be great if instead of going back to the listing, Gmail would open the next or previous mail?

Go to Settings, click on Labs and enable the "Auto-Advance" feature. Now click on General and there select if you would like Gmail to take you to the next mail, previous mail or back to the listing interface when you delete or archive a mail. Depending on your preferences, this could save you a lot of time in navigation.

9) My mail, my shortcuts

A lot of people like to have a set way of custom keyboard mappings across various applications. By default, Gmail has a set of keyboard shortcuts that can be viewed in the help section. However, if you are one of those who like to set your own keyboard shortcuts for various functions, then you are in luck.

Go to Settings, click on Labs and enable the "Custom Keyboard shortcuts" feature. Now, under Settings, you will see "Keyboard shortcuts". Simply click on that and customize shortcuts for various functions as per your choice.

10) Personal toys

Although Gmail offers a lot of features, it doesn't offer everything for everybody. However, if you enable the "Add any gadget by URL" feature under Settings > Labs, it opens a whole new dimension for adding what you need to your sidebar. Once enabled, go to Settings and click on "Gadgets".

Here in the box that says add a gadget by its URL, simply search for a gadget on Google that suits your need and add it. There are already a bunch of gadgets available that integrate various social network feeds on sidebar as well as add functionality such as reminders, URL shorter etc.

Note: Whenever you enable any of these features, Gmail reloads to show the new controls and add-ons.

As it turns out, there isn't much to the boot process:

1. A boot loader finds the kernel image on the disk, loads it into memory, and starts it.

2. The kernel initializes the devices and its drivers.

3. The kernel mounts the root filesystem.

4. The kernel starts a program called init.

5. init sets the rest of the processes in motion.

6. The last processes that init starts as part of the boot sequence allow you to log in.

Identifying each stage of the boot process is invaluable in fixing boot problems and understanding the system as a whole. To start, zero in on the boot loader, which is the initial screen or prompt you get after the computer does its power-on self-test, asking which operating system to run. After you make a choice, the boot loader runs the Linux kernel, handing control of the system to the kernel.

There is a detailed discussion of the kernel elsewhere in this book from which this article is excerpted. This article covers the kernel initialization stage, the stage when the kernel prints a bunch of messages about the hardware present on the system. The kernel starts init just after it displays a message proclaiming that the kernel has mounted the root filesystem:

VFS: Mounted root (ext2 filesystem) readonly.

Soon after, you will see a message about init starting, followed by system service startup messages, and finally you get a login prompt of some sort.

Note: On Red Hat Linux, the init note is especially obvious, because it "welcomes" you to "Red Hat Linux." All messages thereafter show success or failure in brackets at the right-hand side of the screen.

Most of this chapter deals with init, because it is the part of the boot sequence where you have the most control.
init

There is nothing special about init. It is a program just like any other on the Linux system, and you'll find it in /sbin along with other system binaries. The main purpose of init is to start and stop other programs in a particular sequence. All you have to know is how this sequence works.

There are a few different variations, but most Linux distributions use the System V style discussed here. Some distributions use a simpler version that resembles the BSD init, but you are unlikely to encounter this.

Runlevels

At any given time on a Linux system, a certain base set of processes is running. This state of the machine is called its runlevel, and it is denoted with a number from 0 through 6. The system spends most of its time in a single runlevel. However, when you shut the machine down, init switches to a different runlevel in order to terminate the system services in an orderly fashion and to tell the kernel to stop. Yet another runlevel is for single-user mode, discussed later.

The easiest way to get a handle on runlevels is to examine the init configuration file, /etc/inittab. Look for a line like the following:

id:5:initdefault:

This line means that the default runlevel on the system is 5. All lines in the inittab file take this form, with four fields separated by colons occurring in the following order:
# A unique identifier (a short string, such as id in the preceding example)
# The applicable runlevel number(s)
# The action that init should take (in the preceding example, the action is to set the default runlevel to 5)
# A command to execute (optional)

There is no command to execute in the preceding initdefault example because a command doesn't make sense in the context of setting the default runlevel. Look a little further down in inittab, until you see a line like this:

l5:5:wait:/etc/rc.d/rc 5

This line triggers most of the system configuration and services through the rc*.d and init.d directories. You can see that init is set to execute a command called /etc/rc.d/rc 5 when in runlevel 5. The wait action tells when and how init runs the command: run rc 5 once when entering runlevel 5, and then wait for this command to finish before doing anything else.

There are several different actions in addition to initdefault and wait, especially pertaining to power management, and the inittab(5) manual page tells you all about them. The ones that you're most likely to encounter are explained in the following sections.

respawn

The respawn action causes init to run the command that follows, and if the command finishes executing, to run it again. You're likely to see something similar to this line in your inittab file:

1:2345:respawn:/sbin/mingetty tty1

The getty programs provide login prompts. The preceding line is for the first virtual console (/dev/tty1), the one you see when you press ALT-F1 or CONTROL-ALT-F1. The respawn action brings the login prompt back after you log out.

ctrlaltdel

The ctrlaltdel action controls what the system does when you press CONTROL-ALT-DELETE on a virtual console. On most systems, this is some sort of reboot command using the shutdown command.

sysinit

The sysinit action is the very first thing that init should run when it starts up, before entering any runlevels.

How processes in runlevels start

You are now ready to learn how init starts the system services, just before it lets you log in. Recall this inittab line from earlier:

l5:5:wait:/etc/rc.d/rc 5

This small line triggers many other programs. rc stands for run commands, and you will hear people refer to the commands as scripts, programs, or services. So, where are these commands, anyway?

For runlevel 5, in this example, the commands are probably either in /etc/rc.d/rc5.d or /etc/rc5.d. Runlevel 1 uses rc1.d, runlevel 2 uses rc2.d, and so on. You might find the following items in the rc5.d directory:

S10sysklogd S20ppp S99gpm
S12kerneld S25netstd_nfs S99httpd
S15netstd_init S30netstd_misc S99rmnologin
S18netbase S45pcmcia S99sshd
S20acct S89atd
S20logoutd S89cron

The rc 5 command starts programs in this runlevel directory by running the following commands:

S10sysklogd start

S12kerneld start

S15netstd_init start

S18netbase start
...
S99sshd start

Notice the start argument in each command. The S in a command name means that the command should run in start mode, and the number (00 through 99) determines where in the sequence rc starts the command.

The rc*.d commands are usually shell scripts that start programs in /sbin or /usr/sbin. Normally, you can figure out what one of the commands actually does by looking at the script with less or another pager program.

You can start one of these services by hand. For example, if you want to start the httpd Web server program manually, run S99httpd start. Similarly, if you ever need to kill one of the services when the machine is on, you can run the command in the rc*.d directory with the stop argument (S99httpd stop, for instance).

Some rc*.d directories contain commands that start with K (for "kill," or stop mode). In this case, rc runs the command with the stop argument instead of start. You are most likely to encounter K commands in runlevels that shut the system down.

Adding and removing services

If you want to add, delete, or modify services in the rc*.d directories, you need to take a closer look at the files inside. A long listing reveals a structure like this:

lrwxrwxrwx . . . S10sysklogd -> ../init.d/sysklogd
lrwxrwxrwx . . . S12kerneld -> ../init.d/kerneld
lrwxrwxrwx . . . S15netstd_init -> ../init.d/netstd_init
lrwxrwxrwx . . . S18netbase -> ../init.d/netbase
...

The commands in an rc*.d directory are actually symbolic links to files in an init.d directory, usually in /etc or /etc/rc.d. Linux distributions contain these links so that they can use the same startup scripts for all runlevels. This convention is by no means a requirement, but it often makes organization a little easier.

To prevent one of the commands in the init.d directory from running in a particular runlevel, you might think of removing the symbolic link in the appropriate rc*.d directory. This does work, but if you make a mistake and ever need to put the link back in place, you might have trouble remembering the exact name of the link. Therefore, you shouldn't remove links in the rc*.d directories, but rather, add an underscore (_) to the beginning of the link name like this:

mv S99httpd _S99httpd

At boot time, rc ignores _S99httpd because it doesn't start with S or K. Furthermore, the original name is still obvious, and you have quick access to the command if you're in a pinch and need to start it by hand.

To add a service, you must create a script like the others in the init.d directory and then make a symbolic link in the correct rc*.d directory. The easiest way to write a script is to examine the scripts already in init.d, make a copy of one that you understand, and modify the copy.

When adding a service, make sure that you choose an appropriate place in the boot sequence to start the service. If the service starts too soon, it may not work, due to a dependency on some other service. For non-essential services, most systems administrators prefer numbers in the 90s, after most of the services that came with the system.

Linux distributions usually come with a command to enable and disable services in the rc*.d directories. For example, in Debian, the command is update-rc.d, and in Red Hat Linux, the command is chkconfig. Graphical user interfaces are also available. Using these programs helps keep the startup directories consistent and helps with upgrades.

Hint: One of the most common Linux installation problems is an improperly configured XFree86 server that flicks on and off, making the system unusable on console. To stop this behavior, boot into single-user mode and alter your runlevel or runlevel services. Look for something containing xdm, gdm, or kdm in your rc*.d directories, or your /etc/inittab.

Controlling init

Occasionally, you need to give init a little kick to tell it to switch runlevels, to re-read the inittab file, or just to shut down the system. Because init is always the first process on a system, its process ID is always 1.

You can control init with telinit. For example, if you want to switch to runlevel 3, use this command:

telinit 3

When switching runlevels, init tries to kill off any processes that aren't in the inittab file for the new runlevel. Therefore, you should be careful about changing runlevels.

When you need to add or remove respawning jobs or make any other change to the inittab file, you must tell init about the change and cause it to re-read the file. Some people use kill -HUP 1 to tell init to do this. This traditional method works on most versions of Unix, as long as you type it correctly. However, you can also run this telinit command:

telinit q

You can also use telinit s to switch to single-user mode.

Shutting down

init also controls how the system shuts down and reboots. The proper way to shut down a Linux machine is to use the shutdown command.

There are two basic ways to use shutdown. If you halt the system, it shuts the machine down and keeps it down. To make the machine halt immediately, use this command:

shutdown -h now

On most modern machines with reasonably recent versions of Linux, a halt cuts the power to the machine. You can also reboot the machine. For a reboot, use -r instead of -h.

The shutdown process takes several seconds. You should never reset or power off a machine during this stage.

In the preceding example, now is the time to shut down. This argument is mandatory, but there are many ways of specifying it. If you want the machine to go down sometime in the future, one way is to use +n, where n is the number of minutes shutdown should wait before doing its work. For other options, look at the shutdown(8) manual page.

To make the system reboot in 10 minutes, run this command:

shutdown -r +10

On Linux, shutdown notifies anyone logged on that the machine is going down, but it does little real work. If you specify a time other than now, shutdown creates a file called /etc/nologin. When this file is present, the system prohibits logins by anyone except the superuser.

When system shutdown time finally arrives, shutdown tells init to switch to runlevel 0 for a halt and runlevel 6 for a reboot. When init enters runlevel 0 or 6, all of the following takes place, which you can verify by looking at the scripts inside rc0.d and rc6.d:

1. init kills every process that it can (as it would when switching to any other runlevel).

# The initial rc0.d/rc6.d commands run, locking system files into place and making other preparations for shutdown.
# The next rc0.d/rc6.d commands unmount all filesystems other than the root.
# Further rc0.d/rc6.d commands remount the root filesystem read-only.
# Still more rc0.d/rc6.d commands write all buffered data out to the filesystem with the sync program.
# The final rc0.d/rc6.d commands tell the kernel to reboot or stop with the reboot, halt, or poweroff program.

The reboot and halt programs behave differently for each runlevel, potentially causing confusion. By default, these programs call shutdown with the -r or -h options, but if the system is already at the halt or reboot runlevel, the programs tell the kernel to shut itself off immediately. If you really want to shut your machine down in a hurry (disregarding any possible damage from a disorderly shutdown), use the -f option.

What is NTFS and FAT32?

They are formats (file systems) for your hard drive. For Windows 98SE and before, FAT32 or FAT16 is the file type for your hard disk. NTFS is the standard for Windows XP. People say that NTFS is faster than FAT32, as it is far superior. Especially when defragmenting, FAT32 is way slower.


When Can You Use This?

When you buy a external harddrive, the standard is FAT32. Annoying. Moreover, some WinXP installations (in particular, XP upgrades) are done on FAT32 drives.


So, Why Use NTFS over FAT32?

Let’s say you have FAT32. You want to unrar a large file (> 4 GB) and Windows tells you that you cannot unpack it because you don’t have enough hard drive space. Even if you do, you’ll still generate this error. This is because FAT32 drives do not support large files on it (anything over 4 GB).



Consequences:

I’m not responsible for your actions! When converting FAT32 to NTFS, you WILL NOT LOSE any files or data; however, there’s always the chance that something can go wrong (remember, it is Microsoft, by the way).

Solution / How to Do It:

You don’t need to install a program to change the filetype from FAT32 to NTFS.

1. Press the Start button.

2. Go to Run…

3. Type in "cmd" without the quotes, press OK.

4. Go to your C:/ folder, by typing in cd\, (or "cd.."just as long till you have reached C:/ ). See above image. Likewise, type in "cd c:\" works, as well.

5. Go to your "My Computer" icon, and see the name of the letter that stands in from of the drive you want to convert!

6. Back in cmd, Press in "CONVERT X: /FS:NTFS" (without the quotes). The X is for the letter your system drive, or external drive name. (see Step 5)

7. On the question ‘convert lost chains top files Y/N?‘ press ‘y‘ and continue.

8. cmd will now check the file system and the rest. If your cmd finishes, your file system is converted to NTFS. You can close down cmd. (If you want to check if it really did finished, go to ‘My Computer’ and right click on the drive, select ‘Properties’ to see what kind of file system it has).

9. If cmd says: ‘X: was not converted to NFTS, the conversion failed etc, you must follow the next steps!

10. As you can see above, my cmd failed the first time. Next solution.

11. Type in "chkdsk X: /f", where X is the letter of your drive. Wait a while to finish.

12. You’ll be asked to ‘convert lost chains top files Y/N?‘ press ‘y‘ and continue. Wait for it to finish.

13. After this, cmd will say that converting was successful. Check it by going to your computer, and single click on the drive to see what kind of file system your drive has. You may need to repeat step 6.




A word of caution: You should always back up your data whenever you experiment something like this just in case.