I have planned to start a computer lab and a library with a study hall for poor children. The facilities will be available for children 24X7. The facilities will be totally free for poor children and children from well to do families have pay a fee and use the facilities. The library will have books on various topics for children as well as teenagers. The computers can be used for writing codes, creating new software, listening to audio CDs. Reading e-books, surfing the internet. But to start a center like this requires a lot of investment on a regular basis. Hence I would like to invite you all out there to contribute your might in making this dream come true. If you want to volunteer, you can very well join me. Waiting for your comments and feedbacks.
Krish
Since Big Money Matt opened up his summer reading list today, let me offer praise to a book, or rather a series of books, that could really change the world.
It’s O’Reilly’s Head First series, and it makes the Dummies series read like they were written for Einstein.
Tim O’Reilly has taken everything he and his company have learned training people in programming for two decades and condensed it into the format of this series. Even I can learn with it.
While I’ve been writing about programming and programmers for decades, I’ve never been able to actually do it. I’m like the sportswriter who can’t hit.
But with the Head First Java book I was actually able to compile something, and comprehend the language’s basics on one reading. With a baseball book like this Rick Reilly could get himself some scratch hits off a real pitcher.
One of the biggest problems in computing today is the shortage of young programmers, and one of the chief reasons for that is a shortage of readable, basic guides which can act as textbooks in high schools.
This is the first series of programming books I’ve ever seen which could actually be used for that. You could even use it in middle schools. It’s that accessible.
The format is the key. There are lots of pictures, lots of puns, lots of white space, and the text is in small, accessible chunks. Then there are a collection of tests at the end of each chapter to emphasize the lesson.
As with any good teacher, the O’Reilly series attacks the material from a variety of angles. If you know it, or you’re a quick learner, you can breeze right through. If you’re like me they try everything possible to make things comprehensible.
I’ve got educators on both sides of my our family, teachers on my side and administrators on my wife’s. Both sides would be very proud of what O’Reilly has achieved here. Any school with interest in putting together some programming classes would be wise to make this series their first-choice text.
Krish
Linux is not Windows, and although there are some similarities, you must realise that there may be a few "new ways of doing things" to learn before you can be comfortable in Linux. Linux is an open-source clone of UNIX, a secure operating system (OS) that predates DOS and Windows and is designed for multiple users. The items in the following list generally apply to any UNIX-based *nix system, such as Linux and the various BSD's. For the purposes of this article, assume that it's all Linux.
Here are the 10 things to know:
1. File hierarchy
Unlike some other OS's that have a file tree for each drive, the Linux file system is one big tree. At the top you have / (Root) and every folder, file, and drive branches off of this Root.
For example, say that you have two hard drives (named a and b), one floppy drive, and one CD-ROM. Let's say that the first hard drive has two partitions (named a1 and a2). In Windows, it would look like this:
+ hard drive a, partition one (hda1): C DriveIn Linux, you have one file system, not the five listed in the Windows example. Each drive is mounted onto the tree and acts just like a folder. The drives could be placed like this:
+ hda1: / (our Root)Unlike the "tower" OS's from Microsoft, where everything is interconnected and depends on each aspect of the system, the Linux OS is spread out like a Market: everything works together for the common good, but vendors (independent parts of the OS) can be excluded, and the OS will still function. Don't want a Media Player or File Manager? Take it out! Your OS will not fall like a broken tower.
This modularity is the reason for so many distributions of Linux (commonly called distros); any person or company can mix and match the programs they find most useful and slap a name on that collection. RedHat, Xandros, SimplyMEPIS, and Suse are all examples of distros.
Some of the larger distros have copycats that use their settings, but change the included programs. This is the Linux way, and the mix-and-match approach gives users more choice in the long run. DistroWatch.com currently lists over 350 distributions of Linux. Many on the list are specialised to serve a specific group of people, but all can be altered to run the same programs.
Because programs are interchangeable, the Graphical User Interface (GUI) is no exception. GUI's give you the look and feel of a modern OS with the mouse, program icons, menus, etc. Any Linux system (well, one that is running on a real computer, not a phone) can run one of many different GUI's, just like it can run many web browsers or different email client programs.
Want your system to look like Windows? Use FVWM with the XP theme. Want it to be fast? Try IceWM. Want it to be more "full featured"?; try GNOME or KDE. All of these GUI's have benefits and drawbacks, but they all present the user with an interface that can be manipulated with a mouse. Although this may result in every Linux screen looking different, all of the GUI's are still doing the same behind-the-scenes work for you; just use your eyes and often it is not hard at all.
3. Hardware, software, and everything in betweenOne thing that Linux doesn't yet have going for it is vendor support. If you really like Intuit's QuickBooks, for example, you cannot natively run it in Linux. There are projects to make Windows programs run in Linux, such as CrossOver Office and Wine, but these work with varying success, depending on the Windows program. Until software companies decide to port their programs to Linux, you will not be able to run them natively.
Not all is lost, however. Open Source software has upward of 15,000 of programs that run natively in Linux. Because these programs are (usually) free of charge, they vary in quality, but the majority of programs are wonderfully written and constantly improved. These programs can import and export non-native file types as well. GNUCash can read those Quickbooks files just fine, and OpenOffice.org can read MSWord *.doc files. If you dislike GNUCash, don't despair. There are other similar programs also available for free, and more and more software companies are releasing Linux versions of their software.
These same issues apply to hardware. Just as you cannot expect just any piece of hardware off the shelf to work with an Apple computer, the same can be said for Linux machines. Most standard hardware works perfectly; hard drives, RAM, flash drives, motherboards, NIC's, and digital cameras usually have little trouble under Linux. Newer, cutting edge hardware is a different story. Until hardware vendors choose to support Linux, the drivers needed to work these pieces of hardware must be written by the Linux community for free and in the community members' spare time.
Therefore, there is a lag behind Windows support since hardware companies often work directly with Microsoft to ensure compatibility, and tend to let Linux volunteers figure out the Linux hardware support on their own. Laptops are notorious for their non-standard hardware; it can be a challenge to map special keys in Linux. The good news here is that vendor support for Linux hardware, like software, is changing for the better as more and more companies see their future in Linux.
Everything in between the hardware and the software in a Linux machine is the kernel. This kernel is what connects the hardware to the software, and an updated kernel is made available via Internet every few weeks; the most current is 2.6.14. If you have hardware that isn't currently supported, there is a chance that a newer kernel could help you out. Installing this kernel yourself isn't always easy, however; that's where Package Managers come into play.
4. Package Managers - Program installation made easy(er)These PM's usually have an on-line repository for their programs. Installing an application is as easy as searching through the program repository and clicking Install. Can't find IceWM or MPlayer in your Package Manager's list? There is always a way to add a new on-line repository that will have what you are looking for. Some examples of Package Managers include Synaptic (based on dpkg and Apt) for Debian (and derivatives); Yum for RedHat (and derivatives); YaST2 for SuSE (and derivatives); and Emerge for Gentoo.
5. PermissionsEach user belongs to one or more groups, and a user can set their file/folder permissions so that others in the group can read but not write the files, or any other combination of R/W/X. These are Group permissions. For example, Joe and Susan are both in Accounting. They can allow the Accounting group access to each other's files, but they can restrict that access from those in the Sales group.
The Others permissions can allow or deny access to these files for anyone outside the Group. These permissions are for the safety of the overall system, as well as for each user's data. Most home users are fine to leave the default permissions alone on their files. The Root user (not to be confused with the / Root of a file system), as the Administrator, has rights to all files and is the only user who can alter system-wide settings. The Root user has their own password, which is used for system maintenance. This distinction prevents a regular user from installing harmful spy ware on the system or deleting important files.
6. Home directory
Windows has My Documents, but where do you put files that aren't documents? Usually on the Windows Desktop! Linux can clutter the desktop too, but each of our users also has a Home directory, usually located at /home/user. Within that Home directory you often have Documents (/home/user/documents), program links, music (/home/user/Music), or whatever we want. We can create files and folders here, and organise or disorganise them as much as we want, just like it was our own personal Home. Depending on how our permissions are set, we can allow or prevent any other user access to these files (except the Root user). 7. Default installation differences
There are a few differences between Linux distributions, such as where some files are kept or what some of the default programs are named. Just knowing that the file system might be a bit different between RedHat and SuSE is a great start. Most users don't need to know what those differences are, but they should be aware that the internal file systems can be a bit different. When asking for help, make sure to let others know which distribution you are running. If you don't have troubles in your system or don't care to set up complex behind-the-scenes operations, don't worry too much about this. 8. CLI, or "how to run"
From the Start-type menu, the xterm program (also called Console) brings you to a Terminal, which looks a bit like a DOS window, but it actually predates and out-powers DOS. This is the Command Line Interface (CLI), the origin of our favorite OS which is present in every Linux distribution. We won't get into the finer details, which can fill books, but the CLI a powerful tool often needed to troubleshoot your computer. If you ask for help on the Internet and someone asks you to run lspci, they want you to start xterm, type lspci, hit enter, and then provide the screen's response.
When you start an xterm, you are your regular user-self with limited powers. To get into Root User mode (see Permissions above) in an xterm, type su [enter], then type the Root password [enter]. Now you have a lot of power so be nice. The Root user can destroy anyone's data, including the system files needed to run Linux. To leave an xterm or su mode, type exit [enter].
9. Ctrl-alt-escape
Ask a network administrator in any large organisation to compare Linux with network operating systems like Windows NT or Novell Open Enterprise Server, and chances are he'll admit that Linux is an inherently more stable and scalable solution. Chances are he'll also admit that when it comes to securing the system from outside attack, Linux is possibly the most difficult of the three to work with.
This perception is not an uncommon one -- many network administrators new to Linux find it hard to transition from a point-and-click security configuration interface to one based on editing complicated and hard-to-locate text files. Most administrators are well aware of the need to manually put in roadblocks and obstacles to trip up would-be hackers and ensure that your company's data stays secure; it's just that in the unfamiliar Linux world, they're not completely sure of their bearings or where to start.
That's where this document comes in. It outlines some easy things administrators can do to make their Linux server more secure and significantly reduce the risk they face. This tutorial lists seven such items.
1. Protect the root account
The root, or superuser, account on a Linux system is like a backstage pass at a Stones concert -- it allows you access to anything and everything. For this reason, it's well worth taking extra steps to protect it. Start by setting a hard-to-guess password for this account with the passwd command, change it on a regular basis, and restrict knowledge of the password to a few (ideally, only two) key people in the organisation.
Next, restrict the terminals that can be used for root access, by editing the file /etc/securetty. To avoid users leaving a root terminal "open", set a timeout for inactive root logins by setting the TMOUT local variable, and ensure that the root command history file (which might contain sensitive information) is disabled by setting the HISTFILESIZE local variable to 0. Finally, enforce a policy of using this account only to perform specific administrative tasks, and discourage users from logging in as root by default.
Tip: Once you've closed these holes, the next step is to require that every normal user account must have a password and ensure that passwords do not use easily-recognisable heuristics such as birthdays, user names or dictionary words.
2. Install a firewall
A firewall lets you filter data packets travelling in and out of your server and ensures that only those packets matching pre-defined rules are permitted to enter or exit. A number of excellent firewalls are available for Linux, and firewall code can even be compiled directly into the kernel. Begin by defining input, output and forwarding rules for packets leaving and entering your network, using the ipchains or iptables commands. Rules may be specified on the basis of IP addresses, network interfaces, ports, protocols or combinations of these attributes; these rules also specify what action (accept, reject, forward) to take when a match occurs. Once the rules are installed, test the firewall extensively to ensure that no holes exist in it. A good firewall is your first line of defence against common attacks like the distributed denial of service (DDoS) attack.
3. Use OpenSSH for network transactions
An important issue in client-server architecture involves the security of data being transmitted over the network. If network transactions take place in plaintext, it is possible for a hacker to "sniff" the data packets being transmitted and thus gain access to sensitive information. You can close this hole by using a secure shell utility like OpenSSH to create a secure encrypted "tunnel" for your data to pass through. Encrypting your connections in this manner makes it extremely hard for unauthorised users to read the data going back and forth between network hosts.
4. Disable unwanted services
Most Linux systems are installed with a wide variety of different services enabled, such as FTP, telnet, UUCP, ntalk and so on. In most cases, these services are rarely used and leaving them active is like leaving your windows open for a burglar to slip in. You can disable these services by commenting them out in the /etc/inetd.conf or /etc/xinetd.conf files and then restarting the inetd or xinetd daemon. Additionally, some services (for example, database servers) may start up by default during the boot process; you can disable these by editing the /etc/rc.d/* directory hierarchy. Many experienced administrators disable all system services, only leaving SSH communication ports open.
5. Use a spam and anti-virus filter
Junk e-mail and viruses annoy your users and can sometimes cause critical network failures. Linux is surprisingly resistant to viruses, but client machines running Windows may be more susceptible. Therefore, it's a good idea to install a spam and virus filter on your mail server itself, to "defang" suspicious messages and reduce the risk of a chain of collapses.
Begin by installing SpamAssassin, a leading open-source tool that uses a combination of different techniques to identify and flag spam; the program also supports user-based whitelisting and graylisting for greater accuracy. Next, install procmail for user-level filtering based on regular expressions; this tool allows automatic filtering of received email into mailboxes, at both a user and system level. Finally, install Clam Anti-Virus, a free anti-virus toolkit that integrates with sendmail and SpamAssassin and supports on-access scanning of email attachments.
6. Install an intrusion detection system
Intrusion detection systems (IDS) are early warning systems that let you know if changes occur on your network. They're a great way to identify (and prove) attempts to break into your system, although at the cost of increased resource consumption and potential red herrings. There are two fairly well-known IDS' you can try: tripwire, which tracks file signatures to detect modifications; and snort, which use rules-based directives to perform real-time packet analysis and search and identify attempts to probe or attack your system. Both packets can generate e-mail alerts (among other actions) and are useful when you suspect your network is being compromised but need definitive proof.
7. Perform regular security audits
When it comes to securing your network, this final step is possibly the most important. Here, you put on a black hat and do your best to circumvent the defences you erected in the previous steps. Doing this provides you with an immediate and objective assessment of how hard your system really is, and identifies potential vulnerabilities that you should fix.
A number of tools are available to help you in this audit: you can attempt to hack your password files using password crackers like Crack and John the Ripper; you can use nmap or netstat to look for open ports; you can sniff the network using tcpdump; and you can try exploiting publicised holes in your installed programs (Web server, firewall, Samba) to see if they offer a way in. If you do manage to find a way past your obstacles, rest assured that others will too; take immediate measures to close the openings.
Protecting your Linux system is an ongoing task, and so you shouldn't rest easy once you've done the steps above. Visit the Linux security forums for more security tips, and be proactive in monitoring and updating the security of your system. Good luck!
Krish
