networking and printing

8/14/2019 networking and printing

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Networking

Net212

How would we network Linux?

TCP/IP is one option

What is TCP/IP and what are some ways to connectcomputers with it?


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TCP/IP (Transport Control Protocol)

Each computer has a phone number, (otherwise knownas an Internet Protocol (IP) Address )

Pc A reaches pc B by specifying its IP address

10.1.1.1 10.1.1.2

____ ____

| pc A| | pc B |

------ -------

I want to talk to 10.1.1.2 (pc B)

TCP/IP

Pc B finds sends to Pc A by specifying its address

10.1.1.1 10.1.1.2

____ ____

| pc A| | pc B |

------ -------

I want to talk to 10.1.1.1 (pc A)

What are some important addresses in

TCP/IP?


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Important TCP/IP addresses

Host address (IP address ofPc A and Pc B)

Subnet mask

Gateway DNS (Domain Name Service)

IP Addresses

Broken down into four octets (8 bits each)

Pc As IP 10.1.1.1

. . .

The values go from 0 255 for each octet.

Subnet masks

How do we get them?


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Classful networking

Look at the first octet to determine the subnet mask.

Class A 1 126 255.0.0.0Class B 127 191 255.255.0.0

Class C 192 - 223 255.255.255.0

What are the subnet masks for these?

10.1.1.1

10.1.1.2

192.168.0.1

168.1.92.100

Subnet mask examples

10.1.1.1 255.0.0.0

10.1.1.2 255.0.0.0

192.168.0.1 255.255.255.0

168.1.92.100 255.255.0.0

Why are subnet masks important?


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Importance of subnet masks

They divide an IP address into two parts: host andnetwork

Example: What is the host id and network id of 10.1.1.1?

Network ID -> 10

Host ID -> 1.1.1

How did I get that? Use Bitwise operations or just compare the subnet mask with the IP address

Class A: Network ID is first octet; Host ID is last three

10.1.1.1 255.0.0.0

/ \

10 1.1.1

Class B: Network ID is first two octets; Host ID is last two

169.1.67.10 255.255.0.0

/ \

169.1 67.10

Class C: Network ID is the first three octets; Host ID is last one

192.168.0.1 255.255.255.0

/ \

192.168.0 1

Bitwise ANDTo get the network ID use bitwise AND

Example: 10.1.1.1 255.0.0.0

1) Convert IP address to binary 00001010.00000001.00000001.00000001

11111111.00000000.00000000.00000000

3) Compare the numbers in the same column If you have 0 and 0, it is 0

If you have 0 and 1, it is 0

If you have 1 and 1, it is 1

00001010.00000000.00000000.00000000

4) Convert the result to decimal 10.0.0.0


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Bitwise XOR (Exclusive OR)Use XOR to get the Host ID

Example: 10.1.1.1 255.0.0.0

1) Convert IP address to binary 00001010.00000001.00000001.00000001

2) Convert Subnet mask to binary 11111111.00000000.00000000.00000000

3) Compare the numbers in the same column If you have 0 and 0 , it is 0

If you have 0 and 1 (subnet mask is 1), it is 0; otherwise it is 1

If you have 1 and 1 , it is 0

00001010.00000000.00000000.00000000

4) Convert the result to decimal 0.1.1.1

What is a gateway?

Allows you communicate with other networks! Gateways perform routing operations

Pc A and Pc B can communicate because they are on the samenetwork.

10.1.1.1 10.1.1.2

____ ____

| pc A| | pc B |

------ -------

Network = 10.0.0.0

Gateway example

PC A wants to communicate with PC C, but its on anothernetwork 11.0.0.0

10.1.1.1 10.1.1.2 ____ ____

| pc A| | pc B |------ -------| -------> |GW| 10.1.1.254

----- |____ || pc C | < ----------- 11.5.5.10


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What about DNS?

We like to avoid IP addresses when possible.

DNS maps names to IP addresses

We specify names instead of an IP

Examples:

PcA 10.1.1.1

PcB 10.1.1.2

PcC 11.5.5.10

GW 10.1.1.254

netstat

Program to see information about your network

netstat r(view routing table for Pc A)

10.0.0.0 10.1.1.254 255.0.0.0 U 0 0 0 eth0

TCP/IP portsPorts are like phone extensions on your computer.

In order to reach a certain application, you specify its extension (port)

Common port numbers:

FTP 20,21

SSH 22

Telnet 23

SMTP 25

DNS 53

TFTP 69

HTTP 80

POP3 110

IMAP3 220


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/etc/services

Check out your port mappings

less /etc/services

#service-name port/protocol aliases

ssh 22/tcp

ssh 22/udp

telnet 23/tcp

telnet 23/udp

Ports example

PC A wants to ssh to PC B, so it dials Bs extension

It also has to have a extension in the process

ssh 10.1.1.2

10.1.1.1 10.1.1.2

____ ____ PC A port = 32771

| pc A| | pc B | PC B port = 22

------ -------

ssh 32771 sshd 22

More on ports

They are the way applications communicate togetherover the network

Each server and client has a port

Client ports with each use , but server ports are always thesame


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See your active ports!

netstat ap | less

Proto Recv-Q Send-Q Local Address Foreign Address StatePID/Program Name

tcp 0 0 *.ssh *:* LISTEN 1809/sshd

tcp 0 0 pcb:ssh pca:filenet-rmi ESTABLISHED 2274/1

/sbin/ifconfig

Use this program to list information about your networkadapter

It can also configure it

/sbin/ifconfig print info about network adapters

eth0 Link encap: ethernet Hwaddr 00:20:78:07:6C:DD

inet addr: 10.1.1.1 Bcast:10.255.255.255 Mask:255.0.0.0

.

Configuring eth0

eth0 is your first network adapter (and probably youronly one)

Set up PC A 10.1.1.1 255.0.0.0

/sbin/ifconfig eth0 10.1.1.1 netmask 255.0.0.0

Syntax:

ifconfig interface ip_address netmasksubnet_mask


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Printing

Linux uses a printing daemon called CUPS (CommonUnix Printing System)

It responds to a number of utilities configuration files The configuration files are in /etc/cups

/etc/printcap file with the name of your queues

How to printUse the lpr command; stands for line print

lprthe_file

lpr myfile

Wil l acce t i es

ls l | lpr

Specify another queue

lpr Pqueue the_file

lpr Php4000 myfile

See a queues status

See the status of all queueslpstat a

epson360 accepting requests since Jan 01 00:00

See the status of files sent to the default queue

lpqepson360 is ready and printing

Rank Owner Job File(s) Total Size

1ststudent 440 (stdin) 1000 bytes

2nd root 441 myfile 1021 bytes

See whether a queue is down/usr/sbin/lpc status your_queue_here


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Removing jobs

Remove all jobs

lprm

Remove jobs for a user

lprm user_name

lprm student

Root can delete anyones job. A regular account can onlydelete his/her own jobs

How the printing works

Printing is controlled by cupsd

Only root can print to the printer device file (/dev/lp0)directly, so everyone uses cups system.

1) rint to using pror p anot er printingprogram)

2) If you using printer features set up the job using CUPScalls

3) CUPS receives the job and stores it in /var/spool/cups

4) If the job is not text it processed through a filter, so the

printer can understand it

Postscript and PPDs

Usually print jobs are postscript files, which are giganticprograms that tell the printer how to print a file

They are generated for each non-plaintext print file

PPD (postscript printer definition) files describe theprinters features, so a CUPS-aware application can takeadvantage of them

Non-postscript printers can be printed to as well, sinceghostscript helps CUPS convert postscript into theprinters native language.


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Printer definitions

The default driver database is pretty extensive.

You can extend it by updating CUPS from these packages:

Foomatic

GIMP Print

ESP Print Pro

NFS (Network File System) Sharing

Like SMB (server message block) on Windows

It is a file sharing subsystem specified by SunMicrosystems and standardized by IEEE

Allows you to use files on remote machines as if theywere local.

NFS Servers

It is a file server that exports folders from its localfilesystem to the outside

An adminstrator configures folders to shares (exports)inside /etc/exports

10.1.1.1 10.1.1.2

____ ____

| pc A| | pc B | NFS Client: mounting /exports/data

------ -------

NFS Server: exporting /exports/data


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NFS services

Client willl use RPC (remote procedure call) to connectto the server for an export

You should start portmap, lockd, and statd before mountinga NFS volumes. Do so as root.

portmap directs a remote machine to the RPCfunction call its looking for

lockd/statd provides file locking mechanisms (protectagainst multiple people trying to access a file)

Connecting a client to NFS

1. Make sure statd and portmap are started. Use/usr/sbin/rpcinfo p to check

Start them (as root): /sbin/portmap; /sbin/rpc.statd

2. Check that you can see the servers mounts showmount e pca

/exports/data (everyone)

3. Create a mount folder mkdir /mnt/data

4. Mount the export mount server_name:/path/to/export /mnt/point

mount pca:/exports/data /mnt/data

Other NFS client commands

Check that it was mounted

mount

pca:/exports/data on /mnt/data type nfs (rw,addr=10.1.1.1)

umount /mnt/point

umount /mnt/data


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More NFS configurations

Use fstab ... Add this entry

pca:/exports/data /mnt/data nfs defaults

Now you can mount it like so: mountca:/ex orts/data

You can also configure automount to mount an NFSvolume on demand

networking and printing

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