Operating system's file system structure

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Que.1-Discuss the organization of the file system in terms of directories and configuration files?

Answer

An operating system's file system structure is its most basic level of organization almost all of the ways an operating system interacts with its user, application and security model are developed upon the way it stores its files. It can be seen in terms of two different logic categories of files.

Shareable Files vs. unshearable Files

Variable Files vs. Static Files

Shareable files are those that can be accessed by various host and unshareable file are not available to any other host.

Variable files are those that can be accessed and changed at any time without system administrator intervention and static files are not available t

The way in which the operating system and its users need to utilize the files determines the directory where those files should be placed, whether the directory is mounted read-only or read-write and the level of access allowed on each file. The top level of this org is crucial as the access to the underlying directories can be restricted or security problems may manifest themselves if the top level is left disorganized or without or without a widely utilized structure.   .

1. /root Directory

This directory represent s the root user's home directory.

2. /dev Directory

This directory contains file system entries that represent devices that are attached to the system. These files are essential for the system to function properly.

3. /etc Directory

This directory is reserved for configuration files that are local to a machine. The 'X11' and 'skel' directories should be sub-directories of '/etc'. The 'X11' directory is for configuration files such as 'XF86Config'. The 'skel'  directory is for skeleton user files that are used to populate the /home.

4. /etc/sysconfig Directory

This directory stores configuration information, many scripts that run at boot time use the files in this directory.

This directory stores configuration information, many scripts that run at boot time use the files in this directory

5. /lib Directory

This directory should contain only those libraries that are needed to execute the binaries in '/bin' and '/sbin'. These shared library images are particularly important for booting the system and executing commands within the root filesystem.

6. /mnt Directory

This directory refers to temporary mounted filesystem or remote filesystem and storage media such as CD ROM.

7. /bin Directory

This directory contains the common kiu user command,

8. /sbin Directory

This directory contains executables used only by the root user.

9. /usr Directory

This directory contains files that can be said across a whole side.

10. /usr/local Directory

The directory is for use by the system administrator when installing software locally..

11. /var Directory

This directory contains variable data files, which includes spool directories and files, administrative and logging data, and transient and temporary files.

12. /opt Directory

This directory provides an area for usually large, static application software packages to be stored.

13. /tmp Directory

This contains temporary file used by application

Question2. Discuss the function of switch?

Answer:

A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model.

Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub.

Function

The network switch, packet switch (or just switch) plays an integral part in most Ethernet local area networks or LANs. Mid-to-large sized LANs contain a number of linked managed switches. Small office, home office (SOHO) applications typically use a single switch, or an all-purpose converged device such as gateway access to small office/home office broadband services such as DSL router or cable Wi-Fi router. In most of these cases, the end user device contains a router and components that interface to the particular physical broadband technology, as in the Linksys 8-port and 48-port devices. User devices may also include a telephone interface to VoIP.

In the context of a standard 10/100 Ethernet switch, a switch operates at the data-link layer of the OSI model to create a different collision domain per switch port. If you have 4 computers A/B/C/D on 4 switch ports, then A and B can transfer data between them as well as C and D at the same time, and they will never interfere with each others' conversations. In the case of a "hub" then they would all have to share the bandwidth, run in Half duplex and there would be collisions and retransmissions. Using a switch is called micro-segmentation. It allows you to have dedicated bandwidth on point to point connections with every computer and to therefore run in Full duplex with no collisions.

Role of switches in networks

Network switch is a marketing term rather than a technical one. Switches may operate at one or more OSI layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch, although use of the term is diminishing.

In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, including Ethernet, Fibre Channel, ATM, ITU-T G.hn and 802.11. This connectivity can be at any of the layers mentioned. While Layer 2 functionality is adequate for speed-shifting within one technology, interconnecting technologies such as Ethernet and token ring are easier at Layer 3.

In other cases, the switch is used to create a mirror image of data that can go to an external device. Since most switch port mirroring provides only one mirrored stream, network hubs can be useful for fanning out data to several read-only analyzers, such as intrusion detection systems and packet sniffers.

Question3. In this days why we use the Internet and what are the main services of internet.

Answer

The internet has opened the world to people who cannot see or hear it. the internet is capable of answering just about any question. these are the good points.

Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by copper wires, fiber-optic cables, wireless connections, and other technologies. The Internet carries a vast array of information resources and services, most notably the inter-linked hypertext documents of the World Wide Web (WWW) and the infrastructure to support electronic mail. In addition it supports popular services such as online chat, file transfer and file sharing, gaming, commerce, social networking, publishing, video on demand, and teleconferencing and telecommunications. Voice over Internet Protocol (VoIP) applications allows person-to-person communication via voice and video.

The origins of the Internet reach back to the 1960s when the United States funded research projects of its military agencies to build robust, fault-tolerant and distributed computer networks. This research and a period of civilian funding of a new U.S. backbone by the National Science Foundation spawned worldwide participation in the development of new networking technologies and led to the commercialization of an international network in the mid 1990s, and resulted in the following popularization of countless applications in virtually every aspect of modern human life. As of 2009, an estimated quarter of Earth's population uses the services of the Internet

Services

Information

Many people use the terms Internet and World Wide Web (or just the Web) interchangeably, but, as discussed earlier, the two terms are not synonymous. The World Wide Web is a global set of documents, images and other resources, referenced and interconnected by Uniform Resource Locators (URLs) and hyperlinks. These URLs allow users to address the web servers and other devices that store these resources and access them as required using the Hypertext Transfer Protocol (HTTP). HTTP is only one of the communication protocols used on the Internet. Web services may also use HTTP to allow software systems to communicate in order to share and exchange business logic and data.

Software products that can access the resources of the Web are often called user agents. In normal use, web browsers, such as Internet Explorer, Firefox, Opera, Apple Safari, and Google Chrome, let users navigate from one web page to another via hyperlinks. Documents on the web may contain any combination of computer data, including graphics, sounds, text, video, multimedia and interactive content including games, office applications and scientific demonstrations. Through keyword-driven Internet research using search engines like Yahoo! and Google, users worldwide have easy, instant access to a vast and diverse amount of online information. Compared to printed encyclopedias and traditional libraries, the World Wide Web has enabled a sudden and extreme decentralization of information and data.

Advertising on popular web pages can be lucrative, and e-commerce or the sale of products and services directly via the Web continues to grow. In the early days, web pages were usually created as sets of complete and isolated HTML text files stored on a web server. More recently, websites are more often created using content management or wiki software with, initially, very little content. Contributors to these systems, who may be paid staff, members of a club or other organization or members of the public, fill underlying databases with content using editing pages designed for that purpose, while casual visitors view and read this content in its final HTML form. There may or may not be editorial, approval and security systems built into the process of taking newly entered content and making it available to the target visitors

Communication

E-mail is an important communications service available on the Internet. The concept of sending electronic text messages between parties in a way analogous to mailing letters or memos predates the creation of the Internet. Today it can be important to distinguish between internet and internal e-mail systems. Internet e-mail may travel and be stored unencrypted on many other networks and machines out of both the sender's and the recipient's control. During this time it is quite possible for the content to be read and even tampered with by third parties, if anyone considers it important enough. Purely internal or intranet mail systems, where the information never leaves the corporate or organization's network, are much more secure, although in any organization there will be IT and other personnel whose job may involve monitoring, and occasionally accessing, the e-mail of other employees not addressed to them. Pictures, documents and other files can be sent as e-mail attachments.

The idea began in the early 1990s with walkie-talkie-like voice applications for personal computers. In recent years many VoIP systems have become as easy to use and as convenient as a normal telephone. The benefit is that, as the Internet carries the voice traffic, VoIP can be free or cost much less than a traditional telephone call, especially over long distances and especially for those with always-on Internet connections such as cable or ADSL. VoIP is maturing into a competitive alternative to traditional telephone service. Interoperability between different providers has improved and the ability to call or receive a call from a traditional telephone is available. Simple, inexpensive VoIP network adapters are available that eliminate the need for a personal computer.

Data transfer

File sharing is an example of transferring large amounts of data across the Internet. A computer file can be e-mailed to customers, colleagues and friends as an attachment. It can be uploaded to a website or FTP server for easy download by others. It can be put into a "shared location" or onto a file server for instant use by colleagues. The load of bulk downloads to many users can be eased by the use of "mirror" servers or peer-to-peer networks. In any of these cases, access to the file may be controlled by user authentication, the transit of the file over the Internet may be obscured by encryption, and money may change hands for access to the file. The price can be paid by the remote charging of funds from, for example, a credit card whose details are also passed-usually fully encrypted-across the Internet. The origin and authenticity of the file received may be checked by digital signatures or by MD5 or other message digests. These simple features of the Internet, over a worldwide basis, are changing the production, sale, and distribution of anything that can be reduced to a computer file for transmission. This includes all manner of print publications, software products, news, music, film, video, photography, graphics and the other arts. This in turn has caused seismic shifts in each of the existing industries that previously controlled the production and distribution of these products.

Streaming media refers to the act that many existing radio and television broadcasters promote Internet "feeds" of their live audio and video streams (for example, the BBC). They may also allow time-shift viewing or listening such as Preview, Classic Clips and Listen Again features. These providers have been joined by a range of pure Internet "broadcasters" who never had on-air licenses. This means that an Internet-connected device, such as a computer or something more specific, can be used to access on-line media in much the same way as was previously possible only with a television or radio receiver. The range of material is much wider, from pornography to highly specialized, technical webcasts. Podcasting is a variation on this theme, where-usually audio-material is downloaded and played back on a computer or shifted to a portable media player to be listened to on the move. These techniques using simple equipment allow anybody, with little censorship or licensing control, to broadcast audio-visual material worldwide.

Webcams can be seen as an even lower-budget extension of this phenomenon. While some webcams can give full-frame-rate video, the picture is usually either small or updates slowly. Internet users can watch animals around an African waterhole, ships in the Panama Canal, traffic at a local roundabout or monitor their own premises, live and in real time. Video chat rooms and video conferencing are also popular with many uses being found for personal webcams, with and without two-way sound. YouTube was founded on 15 February 2005 and is now the leading website for free streaming video with a vast number of users. It uses a flash-based web player to stream and show video files. Registered users may upload an unlimited amount of video and build their own personal profile. YouTube claims that its users watch hundreds of millions, and upload hundreds of thousands, of videos daily.

Accessibility

Commercial Wi-Fi services covering large city areas are in place in London, Vienna, Toronto, San Francisco, Philadelphia, Chicago and Pittsburgh. The Internet can then be accessed from such places as a park bench. Apart from Wi-Fi, there have been experiments with proprietary mobile wireless networks like Ricochet, various high-speed data services over cellular phone networks, and fixed wireless services. High-end mobile phones such as smart phones generally come with Internet access through the phone network. Web browsers such as Opera are available on these advanced handsets, which can also run a wide variety of other Internet software. More mobile phones have Internet access than PCs, though this is not as widely used. An Internet access provider and protocol matrix differentiates the methods used to get online.

Many use the World Wide Web to access news, weather and sports reports, to plan and book holidays and to find out more about their random ideas and casual interests. People use chat, messaging and e-mail to make and stay in touch with friends worldwide, sometimes in the same way as some previously had pen pals. Social networking websites like MySpace, Facebook and many others like them also put and keep people in contact for their enjoyment. The Internet has seen a growing number of Web desktops, where users can access their files, folders, and settings via the Internet. Cyber slacking can become a serious drain on corporate resources; the average UK employee spent 57 minutes a day surfing the Web while at work, according to a 2003 study by Peninsula Business Services.

Question4. Discuss Run Level in detail with example.

Answer

The term runlevel refers to a mode of operation in one of the computer operating systems that implement Unix System V-style initialization. Conventionally, seven runlevels exist, numbered from zero to six; though up to ten, from zero to nine, may be used. S is sometimes used as a synonym for one of the levels.

0

Halt

1

Single User

2

Multiuser mode with network enabled

3

Multi User mod with console login only

4

Not used

5

Multi user with display manager as well as console login

6

Reboot

Changing from runlevel 3 to runlevel 5, which allows the GUI to be started, can be accomplished by the root (i.e., administrative) user by issuing the following command:

telinit 5

You can change runlevels using the telinit or init commands

telinit 2

The runlevel command can be used to find both the current runlevel and the previous runlevel by merely typing the following and pressing the Enter key:

/sbin/runlevel

Question5. Write down the steps to connect to the internet through Linux.

Answer

ADSL with Linux

Fortunately (or unfortunately, depending on your relationship with your local telecom company) the telephone company handles most of the heavy lifting during the process of getting Linux to work with an ADSL connection. I went through the process of switching from standard dial-up not too long ago, so the process is fresh in my mind. Here are some of the things I had to do.

Call the ISP. This is pretty important. Sometimes they will offer you Internet service and at the same time arrange for the telephone company to come over and install a splitter which allows you to use the same phone line for data and voice transmission. It is also important that you know if you accept their services, you may have to accept the hardware they recommend (or force on you). There are two main connection options; via router and via modem. They may pretty much obligate you to use one or the other, even selling your their own hardware in the process. In the best case scenario, ask if you can use your own choice of hardware and then hope they say yes.

Choose a router or modem If a modem isn't forced upon you, then it's a good idea to choose the router option. The basic reason for this is that it is usually platform independent which means that it doesn't matter what OS you're using because you can probably configure it using Telnet (in my case) or even a web browser, which I have also seen done. For example, in my case, I chose a router that had capabilities for filtering out unwanted incoming connections. This is very important for security because you're going to be connected 24 hours a day. This is a great option for a small business because a router allows you to painlessly share the connection between multiple computers.

Get an Ethernet card If you go the router route (pardon the pun), you're going to need an Ethernet card. These cards are designed to allow you to connect computers in a Local Area Network (LAN). My card of choice (because it was the only one they sold in my area) is the NE-2000 clones. Realtek 8029 PCI is the one I use in my machines in my home office. This is a good one because most major distributions will detect this (they always have for me) during a standard install of Linux. Plus, even if you've never looked under the hood of your PC you can muster up your courage and install this card yourself. For the faint-hearted, I have even heard of the telecom people doing this for you. You can also call your local guru. I encourage people to do it for themselves. It's a question of using a small screwdriver. What that's in, you connect the router to the Ethernet card so your PC can receive the data. If you've got more than one PC in the house, you should get an Ethernet hub to distribute the connection between PCs.

Putting in all together

A picture speaks a thousand words, so I made a little drawing of my home network to demonstrate what a possible set up might look like. (graphics courtesy of The GIMP It's really too good of a program for my poor artistic skills!)

Two cables (red) come from the splitter. One is for the phone and one goes to my router. One Ethernet cable (green) goes from the router to the hub. Other Ethernet cables (blue) go from the hub to the PCs.

Now, to get on the highway

My home network is a private local area network, so each PC is assigned an IP address which is a number that computers identify themselves with. In case you didn't know, when you go to www.linux.org, you're actually going to a computer that is assigned a number on the Internet. In my home, these numbers start with 192.168. and then have two numbers after these. The numbers 192.168.X.X are reserved for private networks, so you will have to use these. If you used any other numbers, they might conflict with numbers that are actually out there on the Internet. I assigned my PCs the numbers 192.168.0.1, 192.168.0.2, 192.168.0.3, 192.168.0.4 respectively.

Now, when the telecom people came to hook me up, I took out my router and connected it to the data line coming from the splitter (see the picture). Then I hooked up the router to the hub and then one of my PCs to the hub. In my case, the manufacturer of the router in the factory assigned the number 192.168.1.1 to the router, so as soon as I turned it on, you could say for all intents and purposes that I had another computer on my local network with the address of 192.168.1.1. The router was equipped with the possibility of using a a program on a CD to configure the Internet connection if I was using Microsoft Windows or Telnet for another OS, like Linux.

Before I used Telnet to access this router, I had to know what address my telecom company had assigned to me for Internet purposes. That is to say, when you use the Internet, you don't identify yourself to other computers with 192.168.X.X. With ADSL you are assigned a unique number with which to connect to other computers. This number has to be unique. It's a lot like running a men's bowling team. If there are 20 members and 7 of them are named Bob then, if someone announces that "e;Bob has the highest score" then there's going to be confusion. In my case, I was given a unique number, let's say it was 20.20.20.20. Then I used Telnet to access the router. I opened a terminal in my PC and typed:

telnet

then:

open 192.168.1.1

which was the local numbered address the router came with by default. They also furnished me with a default password which I used to connect to the router.

Once in, I had a text mode menu (the best you can do with Telnet) and going by the router's manual plus my local telecom's instructions, I assigned the router the unique Internet numbered address my telecom had given me and then I changed the address of the actual router to 192.168.0.5, to me more in synch with my local network's numbering scheme and then I changed the password to access the router. I saved the changes and exited. Now, at least, I had ADSL service coming in to the router.

The final step was to tell the PCs where to get their Internet connection from. I was using my workstation to configure the router, so I logically started with that one. I run SuSE Linux on this machine, so I had to change 2 files: /etc/route.conf and /etc/resolv.conf. The changes I had to make took all of 30 seconds.

First, in /etc/route.conf, I had to write the line:

default 192.168.0.5  0.0.0.0 eth0

Which means that 192.168.0.5 is the default "gateway" to the Internet, or where the machine is going to route out of to get to the outside. 0.0.0.0 is the subnet mask (not important for our discussion here) and eth0 stands for your Ethernet card that you installed and is connected to the hub which is connected to the router.

Then I added two lines to my /etc/resolv.conf file.

nameserver 30.30.30.30

nameserver 40.40.40.40

These are not the actual numbers I was given. It's just an example I used to correspond to the numbers that could be given to you by your telecom company. These are the primary and secondary DNS numbers. DNS stands for Domain Name Server. A domain name server is just a machine that has an inventory of other computers on the Internet. If you're using Mandrake or Red Hat, instead of /etc/route.conf you'll have to add two lines to /etc/sysconfig/network . These are the lines I added:

GATEWAY=192.168.0.5

GATEWAYDEV=eth0

The changes to /etc/resolv.conf are the same.

You're on line - let's be careful out there

After doing all this, I was on line with all machines going out through the router. I quickly disconnected the hub to all but one machine and following the instructions, and set up some necessary security. This is important because you are a sitting duck for intruders with ADSL. You may not think that your local home network might be important compared to some corporate website (which, it really isn't as far as a target for hard-core hackers/crackers) but there are a lot of mischievous people with time on their hands that go around looking for trouble. These people use tools they get off the Internet to scan numbers at random to see if the machine attached to the number can be "hacked". Most of these people, popularly known as "Script Kiddies" seldom know how the software works and really don't care. They just know they can do harm with it. As they say, a little knowledge is a dangerous thing. IRC chat is a good place to chat with friends and also a good place to inadvertently invite people to take a swipe at your machine. Most people on IRC are there to socialize, seek technical help and even work and collaborate on projects at a distance. But there are a few people with dubious social skills who are just on IRC to be jerks. A lot of these people are script kiddies who like to get in feuds with people on channels. Seeing as IRC can tell a lot about where you are, you are somewhat vulnerable to these socially unacceptable characters and what they may try to do with you. Remember, they don't have to know how the program works, only what it does. Report any threats to the channel operators. Sometimes the person's ISP figures in the information on IRC. Report them to their ISP or the local authorities if they threaten to do harm to your machine.

Security with ADSL

Security in Linux is way out of the scope of this beginners' course on Linux. There are a couple of things that you can do without having to be a guru on security to help secure your Linux box.

A brief explanation of ports

I was lucky in that my router has the ability to filter packets built into it. Packets are the data that comes in and out of your computer when you're connected to a network, like the Internet. The people who designed the big network of networks came up with the concept of ports - or point of entry to computers from the outside. For example, webservers run on port 80. If a user on a network wants to access a web page on a server, their computer makes a request to port 80 on the server to send them the page. That's a pretty safe port. It has to be. The WWW wouldn't function if it didn't. Actually, it isn't the port itself that should be considered safe or unsafe, it's the software running behind it. Apache's webserver is pretty safe. But, as we have seen with the famous CodeRed worm, Microsoft's webserver IIS isn't. Telnet, for example runs on port 23. That's a port that I told the router not to accept connections to. Telnet is a 'shell' - a way to connect to a remote computer. The passwords you send to connect via Telnet, even though you may see little asterisks (or nothing) can be picked up easily by people who 'sniff' these passwords. I also disabled my computer's ability to accept connection via Telnet. I substituted it with SSH or Secure Shell. SuSE Linux's most recent offering, (v. 7.2 at the time of this writing) enables SSH by default. SSH accepts remote connections that are encrypted or coded. That makes it almost impossible for someone who you don't want to to connect and try to do harm to your computer from the outside. SSH runs on port 22. I also have FTP disabled- (port 21).

Firewalls

A firewall is just a barrier between a network that's inside a home or company and the outside world. If your private network didn't have a firewall, people could just connect to it and see what they wanted. It would be like a house made of glass. People would spend the day throwing stones at it.

Any decent network that's connected to the Internet has a firewall. The subject of firewalls goes way beyond the scope of this beginner's course and I don't pretend to explain how to set up a firewall here. Some big corporations pay people big money to set up firewalls in their organizations and then they get hacked anyway. I always think of Goldfinger's comment in the James Bond movie of the same name when he explains his plan to steal the gold from Fort Knox to a bunch of incredulous Mafiosos. 007's red-headed nemesis says: "It is a bank like any other and banks can be, how do you say- 'knocked off'" If you want a good guide to providing security for your PC running Linux, I suggest you read Bob Toxen's Real World Linux Security: Intrusion Prevention, Detection and Recovery, the best selling book on security from a Linux perspective.

Practical protection for the beginner

A good way to protect your Linux machine, when you don't know too much (yet) about security is by making the following very simple changes in two files: /etc/hosts.deny and /etc/hosts.allow

First, in /etc/hosts.deny add the following line:

ALL : ALL

This is meant to block (1st ALL) services that your computer provides from anybody (2nd ALL) that may try to log in to your machine. Then, if you have more than one computer (a small business or home network) you should add this line in /etc/hosts.allow

ALL : 192.168.0.

This will allow local users to access the computer. There's no reason not to let people locally to log in via the SSH program that we mentioned before. This is OK as long as you trust them. If you are a home user you're probably safe but if you are using this to set up a small business network, I would be a bit more careful. There are all kinds of stories about disgruntled employees taking liberties, revenge, extended vacations with company money, etc.

One last word: This ISN'T a substitute for a firewall or a serious security set up. If you are setting this up on a small business network, please read some books or seek a professional security consultant's help.

Dial-up connections with Linux

Despite the increasing popularity of broadband Internet access and cable company's ventures into the Internet business and their offering of connections, the vast majority of people in the world, at the time of this writing, connect to the Internet via telephone dial-up through the use of a standard modem, usually at speeds ranging from 14.4 to 56 kilobits per second (kbps). The purpose of this lesson, therefore, is to discuss the way to get a dial-up connection running under Linux.

There are modems and then there are "winmodems"

Once upon a time, there were modems (which still exist) where the ability to use it to connect to computer networks, like the Internet, was based on the configuration of the hardware. Nevertheless, companies like Motorola, Rockwell and others developed modems where the configuration of the device was made possible through software more than the embedded programming on the hardware. This software was exclusively compatible with, yes, you guessed it, Microsoft Windows. They became known as "winmodems". Until recently it was impossible to get one of these little jewels in the MS crown running under Linux. If you happen to have one, you could check out Linmodems.org for more information about installing drivers for these to run under Linux. Motorola recently released a set of drivers for their "winmodems".

The best and easiest way, however, of maintaining a dial-up connection is using an external modem or an internal modem where the hardware primarily is designed to handle the connection. Before I had an ADSL connection, I used an external Dynalink 56 kbps modem. The set-up of this modem under SuSE Linux, Red Hat, Mandrake and Slackware was trivial. Before that I used a 38.8 kbps internal modem and a 28.8 kbps one before that, upgrading as the higher speeds became available and their decreasing prices warranted the change.

External Modems

External modems are called that precisely because you have a little box that sits outside your computer. These connect either via a parallel port or a serial port. A parallel port is one that is normally used to connect a printer. A serial port is similar in appearance to the one that is used to connect your mouse. For example, on my workstation, where I am writing this lesson, there are two serial ports, known as "com1" and "com2". As you can remember from our lessons on other subjects such as hard drives and floppy drives, Linux always knows these devices by other names, files that reside within the /dev/ directory. In our case, Linux knows com1 and com2 as /dev/ttyS0 and /dev/ttyS1 respectively (in the computer world, we usually start counting at zero). If you have a serial mouse, this is usually occupying com1 and therefore /dev/ttyS0. If you then get an external modem and you want to use it, you would hook it up to the second serial port, com2, which, as I mentioned, Linux knows as /dev/ttyS1. The trick (really not a trick because there is no difficulty involved) is to alter your Linux configuration so that it knows that you've got an external modem on /dev/ttyS1 so it can communicate with it.

Under SuSE Linux for example, this is quite easy. As 'root' you would fire up their configuration tool called YAST and choose the option 'System Administration' and then the option 'Integrate Hardware into System'. At this point you're asked to choose the hardware you want to configure and obviously you would choose 'Modem configuration' which is the second option. You'll see the various "com" ports available and even, with the newer version of SuSE, USB modem support. If you have a serial mouse, be sure to choose com2 or /dev/ttyS1. You should have your modem set up after you've done this.

If you've installed Red Hat Linux, then you should have no problem setting it up with one of their utilities known as modemtool. If you've installed Mandrake, their tool HardDrake should do the trick. LinuxConf is also an all-purpose tool that includes modem configuration. I have had (and heard of) mixed results with this tool.

Question6. Elaborate network configuration tool.

Answer

Configuration tools

Before I go into the tools to use to get the sound card working, it's important to point out that the Linux kernel needs to be configured to use a sound card. If your kernel doesn't have a clue about what to do with a one, there is precious little tools like sndconfig can do to help you. Luckily, every install I have done in the past year and a half or so of a major Linux distribution has come with a kernel that has sound support in it by default. If you're installing "Joe's Home-brew Linux" distribution (where you must compile your own kernel), then you might be beyond this beginner's Linux course and you probably already know how to make the kernel you want. But if you are a true beginner (that's who this course is for) then you're probably going to get a "made for sound" kernel. The latest versions of Red Hat, SuSE, Mandrake and Debian that I have installed are all sound enabled from the beginning, depending on, of course, whether or not the hardware is mainstream enough to be detected on install. I wrote in a review of Mandrake 7.2 in the Spring of this year (2001) about how it didn't detect my very mainstream Sound Blaster 16 card. The good thing is that Mandrake 7.2 is very much a thing of the past. They're on version 8.1 at the time of this writing and on that same machine, I did a "clean" install (I did not update - I removed 7.2 and installed 8.0 new) and it found and configured my Sound Blaster 16 card without the slightest problem. If the distribution you have installed (or are planning to install) is up-to-date, you should not have a problem.

It is also important to know what type of sound card it is in terms of the slots that it uses on your mother board in your computer. On my machines, the motherboard (that big thing inside a PC that you plug all the cards into) or mainboard as it is also known, will accept ISA Plug and Play cards (bigger slots) and PCI cards (smaller slots). I'm not a USB user, so I won't feign expertise here and give USB guidelines. If you have an ISA PnP card (I have two) you also have to have the ISA PnP tools installed as well as a kernel that can use ISA Plug and Play (also known as plug and pray)

HardDrake Mandrake uses this graphical tool to configure hardware, including sound cards. Using the GUI, you can select the sound card and then push the button that says "launch configuration tool". I suspect that what it is doing is launching sndconfig - which, as I mentioned, is also available for Mandrake.

alsaconf If you're using Debian, this is the package you need to set up sound. The alsa-base package is also required.

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