Basics: How to find Linux Documentation on the World Wide Web
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Posted: 4 Feb 2005
Question: A newbie has had difficulty with the Samba HowTo.
- They did not know how to look up the Linux networking How Tos on the web
- They did not know how to perform basic Ethernet networking using IP address number
- They had difficulty with the examples
This newbie answer will address their problems.
To answer the first part, start up your web browser in Windows or Linux. Try not to use IE because of the security problems. Firefox is a good alternative as it has built in preventatives for a lot of nasties that plague windows users, and some nice extras like tabbed browsing.
To access the Linux How Tos point your browser at http://en.tldp.org/. This will take you to the Linux Documentation Project home page.
Click on the HowTos link or index, or search for networking, or try the other links to find out what you want to know.
Google is another good source of information. A search for basic Linux Ethernet networking bought up these results for me.
There is quite a bit of information already available as you can see, but as you are probably familiar with my writing style, and as it is stuff I cover in my Digital Divide person-to-person tuition, I'll go over it especially for you and the questioner.
The Physical Network Layout
In the Samba how to we have a simple network of two computers, a Linux one called "Pearl" and a Windows one called "Swine". Each has an Ethernet card and are connected via a "crossover" cable, or through an Ethernet hub or switch. A printer is connected to the Windows machine.
A cross over cable which can be obtained at computer stores, connects two computers without the need for a hub. The wires are arranged so the the output of one end goes to the input of the other for each end.
A hub or switch does this for the normal straight through wires.
Here is a diagram of each option.
Configuring the cards
Once the wiring is connected and the computers are switched on, it is time to make sure their Ethernet cards are configured as needed. The card is usually found by the operating system and the user asked to configure it. To modify the services for this network you may have to change the initial configurations. In windows version 98 (I gave up after this version) the networking setup is accessed in the main menu through settings -- control panel -- network. The screens should look like this after modification.
In SUSE 9.x the networking modification is done through the main menu item System -- Yast -- Network Devices -- Network Card. The screens should look like this.
Simple Summary of IP Addresses
Internet Protocol or IP addresses for IP version 4 come in two flavours. One is the familiar www.google.com type called a Domain Name and the other is made up of four groups of numbers separated by dots. If you really need to understand how these numbers are created, then you will find the answer in the HowTo pages at the Linux Documentation Project.
Suffice to say that all IP addresses are numbers and are resolved into familiar names by special Domain Name Servers (DNS) which have lists of number addresses and their matching names.
These servers are looked up by your computer when it is trying to find the number address corresponding to the name you entered in your browser. Your ISP is probably a DNS and it may look up others elsewhere on the Internet to resolve the name. If you know the number of a website you can type this in and bypass the DNS steps.
In a private local area network like this one, Linux often uses a file called "/etc/hosts" to resolve the same type of activity, but for speed it is just as easy to give each machine a fixed number.
Some special numbers are reserved for private networks like this one.
Simply put, the first two groups are fixed and designate the domain, the third group is the sub network and the last group the individual card.
The two most common private network IP address numbers are 10.0.0.0 and 192.168.0.0
The third group can be 0 to 255 and the last 1 to 255. The number 0 in the last group is used to describe the whole sub network.
This explanation is a very simplified.
Just to confuse us the new IP6 standard is going to change all of this as the world was running out of IP addresses and they had to come up with a different numbering scheme that would last a lot longer.
In this answer, I have used the numbers 10.0.0.1 for the Linux card and 10.0.0.2 for the windows card.
The whole network is 10.0.0.0 and the sub network is 0.
Private networks are often called Intranets to differentiate them from the Internet.
The Transmission Control Protocol (TCP) and the Internet Protocol (IP) are used together as in TCP/IP to facilitate communications between our two computers via their Ethernet physical connection.
I hope this explanation hasn't confused you too much. I know Windows uses NetBios names, which makes things very easy to configure, but as time has shown, easy is not secure or robust, and networks need to be both of those. "User Friendly Networking" is another way of saying "There are no Restrictions against the Uninvited". Using names instead of numbers also restricts the machine to only one connection name, so you can't hook up more Screens, keyboards and mouses and have two or more people surfing the net from one physical machine.
Testing the network.
The next step is to test the cards are operational with the correct addresses and then test the connection is working from each machine. Linux and windows have similar tools for doing this low level testing.
In both system command line tools are used. In windows from a DOS shell and in Linux from your favourite shell or console.
In Windows the tools are called ipconfig and ping.
In Linux the are called ifconfig and ping.
These are the screen shots of the Windows tools at work.
Sorry about the IP addresses not being as shown in the Samba howto but I don't actually use windows here at home except for playing a win 3.1 scrabble game. Luckily for me Linux was out by the time win 98 hit the street, so apart from a second hand copy I bought for testing networking I never had all those problems with blue screens of death, viruses, worms, trojans and spyware I read about on the web.
These are the screen shots of the Linux tools at work.
As you can see I have achieved a working connection by following my own instructions. I hope you had the same pleasure.
If all was not well, first suspect the hardware.
Did the ipconfig or ifconfig not work? That means the relevant card isn't working or isn't setup properly.
Try pinging 127.0.0.1 which is the local IP address of your machine. If that works, the settings are incorrect. Check to be sure its settings are correct.
If that test did work the output side of the card may not be working or it could be the cable.
See if the lights on your cards light up and change when you unplug and re plug the cable. If they don't change. Try replacing the cables one at a time.
If you are using a hub or switch try using a different port or a different cable.
Try changing the suspect card for another. Choose one that has good support for your OS.
As a last resort hop along to your nearest Linux user group and ask for help.
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