LN_ch07_Networking_Unix_Linux[2]ch14
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Transcript LN_ch07_Networking_Unix_Linux[2]ch14
1
Credits: Parts of the slides are based on slides created by UNIX textbook authors,
Syed M. Sarwar, Robert Koretsky, Syed A. Sarwar, 2005 Addison Wesley
Jozef Goetz, 2012
expanded by Jozef Goetz, 2012
Objectives
You may ignore all slides with commands started with r*
To describe networks, the Internet and internetworks and
explain why they are used
To discuss briefly the TCP/IP protocol suite, IP addresses,
protocol ports, and internet services and applications
To explain what the client-server software model is and how
it works
To discuss various network software tools for electronic
communication ,
remote login,
file transfer,
remote command execution , and
status reporting
1.
2.
3.
4.
To describe briefly the secure shell
To cover the commands and primitives
Jozef Goetz, 2012
2
Computer Networks and Internet works
When two or more computer
hardware resources are connected
they form a computer network
1.
2.
3.
Jozef Goetz, 2012
Local area Networks (LANs)
Metropolitan area networks (MANs)
Wide area networks (WANs)
An internetwork is a network of
networks
3
A brief history of the Internet
4
• ARPANET (50s and 60s, some universities)
• NSFNET (late 70s, all universities)
• TCP/IP (invention ’74) became the official protocol in
1983.
When NSFNET and the ARPANET were connected, the growth
became exponential
Many regional networks (Canada, Europe, the Pacific) joined up
In mid-80s people began viewing the collection of networks
as the Internet
The glue that holds the Internet together is the TCP/IP
reference model and TCP/IP protocol stack
• ANS (Advanced Networks and Service) by MERIT,
MCI, and IBM took over NSFNET in 1990 as
ANSNET
• ANSNET sold to American Online in 1995.
Jozef Goetz, 2012
The ARPANET
The original ARPANET design.
IMP - Interface Message Processor
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The ARPANET
Growth of the ARPANET (a) December 1969.
(b) July 1970. (c) March 1971. (d) April 1972.
(e) September 1972.
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NSFNET
The NSFNET backbone in 1988.
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Internet Usage
Machine is on the Internet if
8
it runs the TCP/IP protocol stack,
has an IP address, and
can send IP packets to all the other machines on the
Internet
Millions PC can call up an Internet service
provider using a modem, be assigned a
temporary (dynamic) IP address, and send
IP packets to all the other hosts
Jozef Goetz, 2012
Internet Usage
Traditional applications (1970 – 1990)
E-mail
News
Remote login
newsgroups devoted to different
topics)
Using telnet, WinSCP, rlogin, ssh
programs
File transfer
Jozef Goetz, 2012
Using FTP programs
9
Internet Usage
Early ’90s new application the WWW (World
Wide Web)
10
invented by physicist Tim Berbers-Lee brought millions
of nonacademic users
They started using the Mosaic browser (GUI) and then
other browsers
The ch-r of the network was changed from
an academic and military playground to a
public utility
Jozef Goetz, 2012
Architecture of the Internet.
11
A NAP
(Network Access
Point) is a room
full of routers,
at least one per
backbone
Overview of the Internet.
Signal is transferred to the ISP’s (Internet Service
Provider) POP – Point of Present (located in the tel.
switching office) and injected into the ISP’s regional
network
from this point the system is fully digital and
Jozef Goetz, 2012 packet switched
A LAN in the
room connects
all the routers,
so packets can
be forwarded
from any
backbone to any
other backbone
Collection of Subnetworks
12
SNA: Systems Network Architecture
-IBM's mainframe network standards
The Internet is an interconnected collection of many networks.
Jozef Goetz, 2012
X.25 Networks
• Developed during 70's. 1st public data network
interface between public packet-switched networks and customers.
Data packet has a 3-byte header
a 12 bit connection #,
a packet sequence #,
an acknowledgment # etc. and up to 126 bytes of data
• Operate at 64 Kbps, so are very slow and becoming outdated. However
there are still many of them in operation.
• Connection oriented:
Uses:
• Switched Virtual Circuit
established when the first packet is sent
circuit remains for duration of session providing in-order
delivery, and flow control.
• Permanent Virtual Circuit
established by agreement between the customer and the carrier:
Jozef Goetz, 2012
Like a leased line
13
Frame Relay
14
• Takes advantage of modern high-speed reliable digital
phone lines.
Connection oriented.
Property:
In-order delivery, no error control, no flow control,
akin to LAN
• This allows simple protocols with work done by user
computers rather than by the network.
Runs at 1.5 Mbps with few features.
• Customer leases a permanent virtual circuit between two
points.
Jozef Goetz, 2012
this "virtual leased line" means that the wire is shared with
other users at a great price reduction.
Broadband ISDN and ATM
15
Connection oriented.
• ISDN (Integrated Services Digital
Network)
offers cable, video on demand, e-mail, etc.
• ATM (Asynchronous Transfer Mode) early
’90s is underlying
Mechanism inside the tel. system.
Transmits in small fixed-size cells. Not
synchronous.
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Was supposed to merge voice, data, cable TV, telex, telegraph
etc. into a single integrated system – it didn’t happen
Alive, used by carriers for internal transport
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(a) Computer Networks and (b) Internetworks
R - routers
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Why Computer Networks and Internetworks?
Sharing of computer resources
Network as a communication medium
inexpensive, fast, reliable
Cost efficiency
computers, printers, plotters, scanners, files and
software
large computing power available
Less performance degradation
if one computer crashes, the remaining ones are still
up
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Network Models
International Standards
Organization’s Open System
Interconnect Reference Model
(ISO’s OSI 7-Layer Reference Model)
The TCP/IP 5-layer Model
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Used in the Internet
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Network Models
with approximate mapping between the two
•The first 4 layers deal with the
communication between hosts.
•The 5th layer deals with the Internet
services provided by various
applications.
•Most of the 1st layer is handled by
hardware (communication medium used,
attachments of hosts to the medium).
•The rest of the 1st layer and all the
2nd layer is handled by the (Network
Interface Card) NIC card in a host.
•Layers 3 and 4 are fully implemented
in the operating systems kernel on most
existing systems.
Jozef Goetz, 2012
•The first 2 layers are network
hardware specific, the others are work
independently of the physical layer
Reference Models
Protocols and networks in the TCP/IP model initially.
The Application layer contains all of the higherlevel protocols
– telnet - virtual terminal protocol
– FTP
– file transfer
– SMTP – e-mail
– DNS - Domain Name System
– NNTP - Network News Transfer Protocol
– HTTP - Hypertext Transfer Protocol
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The TCP/IP Protocol Suite
As a user you
can see the
application
layer in the
form of
applications
and utilities
1.
2.
3.
4.
Jozef Goetz, 2012
Web
browsing,
file transfer,
remote login
etc.
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The TCP/IP Protocol Suite
IGMP - Internet Group
Management Protocol
handles multicasting
ICMP - Internet Control
Message Protocol
Handles errors and
control messages.
Protocol is used to
forward information,
primarily error
messages.
To see if a computer is
running, the `ping'
program sends an
echo request, which
is part of ICMP.
ARP -Address Resolution
Protocol is a protocol for
mapping an Internet
Protocol IP address to a
physical machine address
(MAC) that is recognized in the
local network.
For example, in IP
Version 4, the most
common level of IP in use
today, an address is 32
bits long.
In an Ethernet LAN,
however, addresses for
attached devices are 48
bits
Jozef Goetz, 2012
RARP - Reverse Address Resolution Protocol is a protocol by
which a physical machine in a LAN can request to learn its IP
address from a gateway server's Address Resolution Protocol
(ARP) table or cache.
A network administrator creates a table in a LAN’s
gateway router that maps the physical machine (MAC
addresses) into IP addresses.
22
Transport Layer: The TCP and UDP
The purpose of the transport layer is to
transport application data from your machine to
a remote machine and vice versa
User Datagram Protocol (UDP) is a
connectionless protocol, offers the best
effort delivery service
Transmission Control Protocol (TCP) is a
connection-oriented protocol that establish a
virtual connection with the destination before
transmitting data,
thus the TCP leads
completely reliable,
error free
in-sequence delivery of data
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Routing of the Application Data
The Internet Protocol (IP)
The network layer is responsible for routing
application data to the destination host
IP is responsible for transporting IP datagrams
containing TCP segments or UDP datagrams to the
destination host
The IP is a connectionless protocol, it simply
sends the application data without establishing
virtual connection with the destination before
transmitting data,
Jozef Goetz, 2012
thus the IP routing is the best effort and
doesn’t guarantee delivery of TCP segments or
UDP datagrams
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Routing of the Application Data
The Internet Protocol (IP)
In IPv4 the IP address (32
bits) is divided into three
fields:
1.
address class,
2.
network ID and
3.
host ID
The address class field
identifies the class of the
address and dictates the
number of bits used in the
network ID and host ID
fields
This scheme has 5 address
classes : A,B,C,D,E
Jozef Goetz, 2012
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IPv4 Addresses in Dotted Decimal Notation
32-bit binary numbers are
difficult to remember
IPv4 addresses are given in
dotted decimal notation
(DDN)
In DDN all 4 bytes of an
IPv4 address are written
in their decimal
equivalents and are
separated by dots
Example: 192.102.10.21
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IP Addresses
IP address formats.
127.0.0.0 (or 127.x.x.x, where x is between 0-127) is known as localhost
is used to send a data packet to itself. for testing purpose.
host ID = 1…1 is the broadcast address in order to send a data packet to all hosts on a
network
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IPv4 Address Classes
The sum of network IDs for class A, B, C = 2^7 + 2^14 + 2^21 = 1,113,664 networks
The sum of hosts IDs
for class A, B, C = 2^24 + 2^16 + 2^ 8 = 3,758,096,400 hosts
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IPv4 Address Classes
Prove all ranges!!!
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IPv4 Address Classes
•A: Very large organizations and government agencies
•B: Large organizations: AT&T, IBM, MIT, large universities etc.
•C: Small to medium sized organizations: ISP, small consulting companies,
community colleges, universities
Jozef Goetz, 2012
In IPv4 the IP address (32 bits)
In IPv6 the IP address is 128 bits and it covers the # of
hosts 6 x 2^28 times the present world population
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IPv4 Address Classes
Figure 14.5 An internetwork of 4 networks with one class A, one class B,
and 2 class C networks connected via 4 routers
class C
class A
class C
Jozef Goetz, 2012
class B
Symbolic Names
32
Symbolic names are easier to remember
remain the same even if the numeric address changes
must be unique for a host on the Internet
Format:
hostname.domain_name e.g. students.up.edu
where:
domain_name = organization_name.top-level_domain
organization_name is assigned by the Network Information Center
e.g. laverne.edu
Attaching the name of a host to a domain name with a
period between them yields the Fully Qualified Domain
Name (FQDN) for the host
e.g. egr.up.edu – egr is a host name at the University of Portland
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A portion of the Internet domain name hierarchy
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Top-Level Internet Domains
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35
Jozef Goetz, 2012
The Domain Name System
Domain Name System (DNS) service
translates symbolic names to equivalent
IP addresses
DNS implements a distributed database of
name-to-address mappings
A set of dedicated hosts run name servers
that take requests from the application
software
and work together to map domain names to
the corresponding IP addresses
every organization runs at least 1 name
server
Jozef Goetz, 2012
app uses gethostbyname() to get its IP address
36
37
Inverse domain
The servers that handle the inverse
domain are also hierarchical.
This means the netid part of the
address should be at a higher level
than the subnetid part, and the
subnetid part higher than the
hosted part.
In this way, a server serving the
whole site is at a higher level than
the servers serving each subnet.
To follow the convention of reading
the domain labels from the bottom
to the top, an IP address such as
132.34.45.121 (a class 13:
address with netid 132.34) is read as
121.45.34.132.in-addr. area.
This configuration makes the
domain look inverted when
compared to a generic or country
domain.
Jozef Goetz, 2012
DNS lookup utility: host
[cs253u@shell cs253u]$ host ecs.fullerton.edu
ecs.fullerton.edu has address 137.151.27.1
[cs253u@shell cs253u]$ host 137.151.27.1
1.27.151.137.in-addr.arpa domain name pointer
ecs.fullerton.edu.
[cs253u@shell cs253u]$
[jgoetz
ulv.edu
ulv.edu
ulv.edu
jgoetz]$ host ulv.edu
has address 192.231.179.66
mail is handled (pri=5) by mxg1.ulv.edu
mail is handled (pri=5) by mxg2.ulv.edu
[jgoetz jgoetz]$ host 192.231.179.66
66.179.231.192.IN-ADDR.ARPA domain name pointer www.ulv.edu
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The Domain Name System
#DNS service is to use a static host file /etc/hosts
#a static hosts file contains the domain names and their IP addresses configured by the system
admin
$ cat /etc/hosts
[jgoetz jgoetz]$ cat /etc/hosts
127.0.0.1
localhost
192.231.179.91 raq4.ulv.edu # Cobalt automated entry for eth0
192.231.179.81 loki.ulv.edu loki
#Veritas Backup Server
#to view IP address and other info about host’s interface to the network
$ /sbin/ifconfig –a
# faculty.ulv.edu has 192.231.179.91
[jgoetz jgoetz]$ /sbin/ifconfig -a
eth0
Link encap:Ethernet HWaddr 00:10:E0:05:A8:F4
inet addr:192.231.179.91 Bcast:192.231.179.95 Mask:255.255.255.224
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:212947098 errors:0 dropped:0 overruns:0 frame:0
TX packets:318162567 errors:3 dropped:0 overruns:0 carrier:3
collisions:0 txqueuelen:100
Interrupt:5 Base address:0x8000
eth1
Link encap:Ethernet HWaddr 00:10:E0:05:A8:F3
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
Interrupt:9 Base address:0x8100
lo
Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:3924 Metric:1
RX packets:1749416 errors:0 dropped:0 overruns:0 frame:0
TX packets:1749416 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
$
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The Domain Name System
[cs253u@shell cs253u]$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1
localhost.localdomain
localhost
shell
192.168.3.25
ldap.int.ecs.fullerton.edu
ldap
192.168.3.29
ecsmysql.ecs.fullerton.edu
ecsmysql
192.168.3.30
mail.ecs.fullerton.edu
mail
137.151.28.223 lupus.ecs.fullerton.edu lupus
192.168.3.200 lupus2.ecs.fullerton.edu lupus2
[jgoetz@raq4 ~]$ host 192.231.179.91
91.179.231.192.IN-ADDR.ARPA domain name pointer FACULTY.ULV.EDU
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40
The Domain Name System
#lookup for the IP address of a host name:
[cs253u@shell cs253u]$ nslookup ecs.fullerton.edu
Server:
192.168.3.26
# name server
Address:
192.168.3.26#53
Name:
Address:
ecs.fullerton.edu
137.151.27.1
[jgoetz jgoetz]$ nslookup ulv.edu
Server: ns.ulv.edu
Address: 64.69.149.200
Name:
ulv.edu
Address: 192.231.179.66
[jgoetz@raq4
Server:
Address:
Name:
Address:
~]$ nslookup faculty.ulv.edu
ns.ulv.edu # this a name server
64.69.149.200
faculty.ulv.edu
192.231.179.91
#nslookup uses file /etc/resolv.conf to find the host that runs the name
server and passes the request over it.
Jozef Goetz, 2012
[jgoetz jgoetz]$ cat /etc/resolv.conf
domain ulv.edu
search ulv.edu
nameserver 64.69.149.200
nameserver 64.69.154.123
[jgoetz jgoetz]$
41
The Domain Name System
nslookup uses file /etc/resolv.conf to find the host
that runs the name server and passes the request over
it.
[cs253u@shell cs253u]$ cat /etc/resolv.conf
nameserver 192.168.3.26
dig interacts with name servers specified in
/etc/resolv.conf and display their responses – gives
more info than nslookup
Jozef Goetz, 2012
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The Domain Name System
[jgoetz@raq4 ~]$ dig faculty.ulv.edu
[jgoetz jgoetz]$ dig ulv.edu
; <<>> DiG 8.3 <<>> faculty.ulv.edu
; <<>> DiG 8.3 <<>> ulv.edu
;; res options: init recurs defnam dnsrch
;; res options: init recurs defnam dnsrch
;; got answer:
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ;;
4 ->>HEADER<<- opcode: QUERY, status:
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2,NOERROR, id: 4
ADDITIONAL: 2
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1,
;; QUERY SECTION:
AUTHORITY: 2, ADDITIONAL: 2
;;
faculty.ulv.edu, type = A, class = IN
;; QUERY SECTION:
;;
ulv.edu, type = A, class = IN
;; ANSWER SECTION:
faculty.ulv.edu.
1D IN A
192.231.179.91
;; ANSWER SECTION:
ulv.edu.
12H IN A
192.231.179.66
;; AUTHORITY SECTION:
ulv.edu.
1D IN NS
ns.ulv.edu.
;; AUTHORITY SECTION:
ulv.edu.
1D IN NS
ns2.ulv.edu.
ulv.edu.
12H IN NS
ns2.ulv.edu.
ulv.edu.
12H IN NS
ns.ulv.edu.
;; ADDITIONAL SECTION:
ns.ulv.edu.
1D IN A
64.69.149.200
;; ADDITIONAL SECTION:
ns2.ulv.edu.
1D IN A
64.69.154.123
ns.ulv.edu.
12H IN A
64.69.149.200
ns2.ulv.edu.
12H IN A
64.69.154.123
;; Total query time: 25 msec
;; FROM: raq4.ulv.edu to SERVER: default -- 64.69.149.200
;; Total query time: 11 msec
;; WHEN: Wed Nov 16 22:25:25 2005
;; FROM: raq4.ulv.edu to SERVER: default -;; MSG SIZE sent: 33 rcvd: 116
64.69.149.200
;; WHEN: Thu Nov 15 16:21:26 2007
;; MSG SIZE sent: 25 rcvd: 108
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The Domain Name System
dig
[jgoetz jgoetz]$ dig ulv.edu
ecs.fullerton.edu
; <<>> DiG 9.2.4 <<>> ecs.fullerton.edu
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR,
id: 29854
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1,
AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;ecs.fullerton.edu.
IN
;; ANSWER SECTION:
ecs.fullerton.edu.
137.151.27.1
86400
;; AUTHORITY SECTION:
ecs.fullerton.edu.
ecs.fullerton.edu.
86400
;;
;;
;;
;;
IN
IN
Query time: 22 msec
SERVER: 192.168.3.26#53(192.168.3.26)
WHEN: Fri Mar 14 23:54:21 2008
MSG SIZE rcvd: 65
Jozef Goetz, 2012
A
A
NS
; <<>> DiG 8.3 <<>> ulv.edu
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status:
NOERROR, id: 4
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1,
AUTHORITY: 2, ADDITIONAL: 2
;; QUERY SECTION:
;;
ulv.edu, type = A, class = IN
;; ANSWER SECTION:
ulv.edu.
12H IN A
192.231.179.66
;; AUTHORITY SECTION:
ulv.edu.
12H IN NS
ulv.edu.
12H IN NS
ns2.ulv.edu.
ns.ulv.edu.
;; ADDITIONAL SECTION:
ns.ulv.edu.
12H IN A
ns2.ulv.edu.
12H IN A
64.69.149.200
64.69.154.123
;; Total query time: 11 msec
;; FROM: raq4.ulv.edu to SERVER: default -64.69.149.200
;; WHEN: Thu Nov 15 16:21:26 2007
;; MSG SIZE sent: 25 rcvd: 108
44
45
Well-known Internet Services
Jozef Goetz, 2012
The Client-Server Software Model
46
Internet services are implemented by using a
paradigm in which the software for a service is
partitioned into 2 parts
The part that runs on the host on which the user
running the application is logged on to is called the
client software
The part that’s usually starts running when a host
boots is called the server software
Connection-oriented client server models:
client sends a connection request to the server
and
the server either rejects or accepts the request.
If server accepts the request, the client and server
are said to be connected through a virtual
connection
Jozef Goetz, 2012
47
The Client-Server Software Model
http://faculty.ulv.edu/
Jozef Goetz, 2012
Displaying the Names.
48
uname [OPTION]...
DESCRIPTION
Print certain system information. With no
OPTION, same as
-s.
-a, --all
print all information
-m, --machine
print the machine (hardware) type
-n, --nodename
print the machine's network node
hostname
-r, --release
print the operating system release
-s, --sysname
print the operating system name
-p, --processor
print the host processor type
-v print the operating system version
--help display this help and exit
--version
output version information and exit
Jozef Goetz, 2012
[jgoetz jgoetz]$ uname
Linux
[jgoetz jgoetz]$ uname -n
raq4.ulv.edu
[jgoetz jgoetz]$ uname -a
[jgoetz jgoetzLinux raq4.ulv.edu
2.2.16C37_V #1 Sat Apr 12 15:06:43 PDT 2003 i686
unknown
Displaying the Host Name
$ uname -n
yamsrv1.ece.gatech.edu
$ uname -a
SunOS yamsrv1.ece.gatech.edu 5.8
Generic_108528-22 sun4u sparc SUNW,Ultra-250
$ hostname – name of the host you are logged on to
yamsrv1.ece.gatech.edu
[jgoetz jgoetz]$ hostname
raq4.ulv.edu
Jozef Goetz, 2012
-a, --all print all information
-m, --machine
print the machine (hardware) type
-n, --nodename
print the machine's network node
hostname
--help
49
cpu info.
[jgoetz jgoetz]$ less /proc/cpuinfo
[cs253u@shell cs253u]$ less /proc/cpuinfo
processor
:1
vendor_id
: AuthenticAMD
cpu family
: 15
model
: 35
model name : Dual Core AMD Opteron(tm) Processor 175
stepping
:2
cpu MHz
: 2211.280
cache size
: 1024 KB
fdiv_bug
: no
hlt_bug
: no
f00f_bug
: no
coma_bug
: no
fpu
: yes
fpu_exception : yes
cpuid level
:1
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext lm 3dnowext
3dnow lahf_
lm pni
/proc/cpuinfo (END)
Jozef Goetz, 2012
50
Displaying Users on a Network
$ rwho | more - remote who displays info about the user
currently using machines on your network: log name,
computer:terminal, date and time the user logged in
Bobk
upibm7:ttyC4
Dfrakes
upibm47:ttyp2
Lulay
upsun17:pts/0
Oster
upsun17:pts/2
Sarwar
upibm7:ttyp2
$ rwho -a | more
Bobk
upibm7:ttyC4
dfrakes
upibm47:ttyp2
kent
upibm48:ttyp0
kittyt
upibm9:ttyp0
kuhn
upsun29:console
lulay
upsun17:pts/0
oster
upsun17:pts/2
pioster
upsun20:pts/0
sarwar
upibm7:ttyp2
sarwar
upsun29:pts/0
$
Jozef Goetz, 2012
Jul
Jul
Jul
Jul
Jul
26
26
26
26
26
12:03
11:49
10:17
12:28
11:15
Jul
Jul
Jul
Jul
Jul
Jul
Jul
Jul
Jul
Jul
26
26
26
26
16
26
26
26
26
26
12:03
11:49
03:41
07:36
13:11
10:17
12:28
09:53
11:15
11:24
8:49
1:28
99:59
2:41
1:00
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Displaying Users on a Network.
rusers [options] [host_list]
Purpose:
Output:
to
line
Display the login names of the remote
users logged on to all the machines on
our local network
Information about the users logged on
the hosts on your local network in one
per machine format
Commonly used options/features:
-a
Display all host names even if no user is
using it
-l
Display the user information in a long
format similar to that displayed by the who
command
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Displaying Users on a Network
for particular machine
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Displaying the Status of Hosts on a Network
ruptime [options] – remote uptime
Purpose:
Output:
Show status of all connected machines on the
local area network
Status of machines including machine name,
up/down status, time a machine has been up
(or down) for-called machine uptime, and the number
of users logged on to the machine
Commonly used options/features after sorting :
-l
Display output after sorting it with load average
-t
Display output after sorting it by machine uptime
-u
Display output after sorting it by the number of users
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Displaying the Status of Hosts on a Network
Commonly used options/features after sorting :
-l
Display output after sorting it with load average
-t
Display output after sorting it by machine uptime
-u
Display output after sorting it by the number of users
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Testing a Network Connection
ping [options] hostname
Purpose:
Output:
Send an IP datagram to ‘hostname’ to test
whether it is on the network (or Internet);
if the host is alive it simply echoes the
received datagram
Message(s) indicating whether
the machine is alive
Commonly used options/features:
-c count
Send and receive ‘count’ (e.g. 3) packets
-f
Send 100 packets per second or as many
as can be handled by the network; only the
superuser can use this option
-s packetsize
Send ‘packetsize’ packets; the default is
56 bytes (plus an 8 byte header)
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Testing a Network Connection
ping -c count
Send and receive ‘count’ packets
ping -s packetsize Send ‘packetsize’ packets; the default is
56 bytes (plus an 8 byte header);
Test yahoo.com
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Displaying Information About Users
finger [options] [user_list]
Purpose:
Display information about the users in the
‘user_list’;
without a ‘user_list’, the command displays
a short status report about all the users
currently logged on to the specified hosts
Output:
User info extracted from the
~/.project and ~/.plan files
Commonly used options/features:
-m
Match ‘user_list’ to login names only
-s
Display output in a short format
[jgoetz@raq4 ~]$ finger Jozef
Login: jgoetz
Name: Jozef Goetz
Directory: /home/sites/site7/users/jgoetz
Shell: /bin/bash
On since Wed Nov 30 21:05 (PST) on pts/1 from 64.69.147.181
No mail.
No Plan.
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Displaying Information About Users
[jgoetz@raq4 ~]$ finger -s Jozef
Login Name
Tty Idle Login Time Office Office Phone
jgoetz Jozef Goetz pts/1
Nov 30 21:05 (64.69.147.181)
[jgoetz@raq4 ~]$
[jgoetz@raq4 ~]$ finger -m jgoetz
Login: jgoetz
Name: Jozef Goetz
Directory: /home/sites/site7/users/jgoetz
Shell: /bin/bash
On since Wed Nov 30 21:05 (PST) on pts/1 from 64.69.147.184
No mail.
No Plan.
-m
-s
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Match ‘user_list’ to login names only
Display output in a short format
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Displaying Information About Users
-m
-s
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Match ‘user_list’ to login names only
Display output in a short format
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Displaying Information About Users
// if the finger server is running
[jgoetz jgoetz]$ finger [email protected]
[ulv.edu]
finger: connect: No route to host
[jgoetz jgoetz]$ [email protected]
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Remote Login.
The telnet protocol is designed to allow you to connect to a remote
computer over a network
telnet [options] [host[port]]
Purpose:
To connect to a remote system ‘host’ via a network; the ‘host’ can
be specified by its name or IP address in dotted decimal notation
Commonly used options/features:
-a
Attempt automatic login
-l
Specify a user for login
usage: telnet [-l user] [-a] host-name [port]
e.g.
titan/bin > telnet -l jgoetz -a faculty.ulv.edu
Trying 192.231.179.91...
Connected to FACULTY.ULV.EDU (192.231.179.91).
Escape character is '^]'.
Password:
Last login: Wed Nov 29 13:00:01 from cpe-66-74- …
telnet help //or
telnet --help // to get available cmds
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Remote Login (contd.)
$ telnet upsun29
Trying 192.102.10.89...
Connected to upsun29.egr.up.edu.
Escape character is ‘^]’.
UNIX(r) System V Release 4.0 (upsun29.egr.up.edu)
login: sarwar
Password: **********
Last login: Sat Dec 27 05:05:37 from up
You have mail.
DISPLAY = (‘)
TERM = (vt100)
$
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64
Remote Login (contd.)
[jgoetz jgoetz]$ telnet -?
telnet: invalid option -- ?
Usage: telnet [-8] [-E] [-L] [-S tos] [-a] [-c] [-d] [-e char] [-l user][-n tracefile] [-b
hostalias ][-r] [host-name [port]]
Ctrl + D close the session
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Remote Login (contd.)
# reverts to the telnet client – place in the foreground
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Using Telnet to Invoke Other Well-known Services
invokes a daytime service running at
port 13
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The rlogin Command
The rlogin command allows you to log on to a host on your local
network (or remote)
rlogin [options] hosts
Purpose:
To connect to a remote LINUX or UNIX ‘host’
via a network ; the ‘host’ can be specified
by its name or IP address in the dotted
decimal notation
Commonly used options/features:
-ec
Set the escape character to ‘c’( the default is ‘~’)
-l user
User ‘user’ as the login name on the remote host
e.g.
[jgoetz jgoetz]$ rlogin -l jozefg ecs.fullerton.edu
ecs.fullerton.edu: Connection refused // it is not a local network
slogin [options] hosts - secure version uses strong cryptography for transmitting data
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The rlogin Command
$ rlogin upsun -l perform
Password:
Last login: Mon Dec 18 12:08:12 from upsun21.up.edu
SunOS Release 4.1.3 (UPSUN_SERVER) #5: Mon Nov 14
17:31:44 PST 1994
DISPLAY 5 (upx46:0.0)
TERM 5 (vt100)
$ whoami
perform
$ hostname
upsun.egr.up.edu
$
-ec
Set the escape character to ‘c’( the default is ‘~’)
-l user
User ‘user’ as the login name on the
remote host
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Remote Command Execution
rsh – remote shell
rsh [options] host [command]
Purpose:
To execute a command on a remote machine ,
‘host’, on the same network;
the rlogin command is executed if no ‘command’ is
specified
Commonly used options/features:
-l user
Use ‘user’ as the login name
on the remote host
ssh [options] host [command] -secure version uses strong
cryptography for transmitting data
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70
Figure 14.8 The semantics of the rsh upsun29 ps command
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The same network
Figure 14.9 The semantics of the
rsh upsun29 sort students > sorted_students command
students and sorted_students are files
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Remote Command Execution
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Remote Command Execution
•the sort cmd takes input from the students file on the
local machine, (upibm7) and the output is sent to the
sorted_students file on the local machine
•input from local file students and store the
sorted result in a sorted_students file on the
remote machine
When used without arguments, the rsh reverts to the rlogin command.
it is executed if no ‘arguments’ is specified
//to log on a different network on the Internet
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File Transfer
ftp [options] [host]
Purpose:
To transfer files from or to a remote ‘host’
Commonly used options/features
-d
Enable debugging
-i
Disable prompting during
transfers of multiple files
-v
Show all remote responses
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File Transfer
titan/jozefg > ftp -v faculty.ulv.edu
// -v Show all remote responses
Connected to faculty.ulv.edu.
220 ProFTPD 1.2.9 Server (ProFTPD) [192.231.179.91]
500 AUTH not understood
500 AUTH not understood
KERBEROS_V4 rejected as an authentication type
Name (faculty.ulv.edu:jozefg): jgoetz
331 Password required for jgoetz.
Password:
230 User jgoetz logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls -l
200 PORT command successful
150 Opening ASCII mode data connection for file list
-rw-r--r-- 1 jgoetz site7
123392 Nov 28 21:01 Assig.doc
-rwxrwxrwx 1 jgoetz site7
13 Oct 31 07:22 m
drwxrwsr-x 4 jgoetz site7
4096 Jun 1 2006 web
226 Transfer complete.
ftp>
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File Transfer
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Remote Copy
rcp[options] [host:]sfile [host:]dfile
rcp[options] [host:]sfile [host:]dir
Purpose:
To copy ‘sfile’ to ‘dfile’
source file –
sfile
destination file - dfile
Commonly used options/features
-p
-r
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Attempt to preserve file modify and access times;
without this option the command uses the current value of
unmask to create file permissions
Recursively copy files at ‘sfiles’ to ‘dir’
78
Remote Copy (contd.)
$ rcp ~/myweb/*.html upsun29:webmirror
$ rcp ~/unixbook/Chapter[1-9].doc upsun29:unixbook.backup
$ rcp upsun29:ece446/projects/*.[c,C] ~/swprojects.backup
$ rcp -rp www1:* www2:
$
-p Attempt to preserve file modify and access times;
-r Recursively copy files at ‘sfiles’ to ‘dir’
Secure version of the rcp command
$ scp prog4.c upsun29:~/courses/cs213/programs/
$ scp -r upsun21.egr.up.edu:courses.
$ scp -rp www1:* www2:
$
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Interactive Chat
talk user [tty]
Purpose:to initiate interactive chat
with ‘use’ who is logged in
on a ‘tty’ terminal
$ talk bob
[Waiting for your party to respond]
Message from [email protected] at 13:36 ...
talk: connection requested by [email protected].
talk: respond with: talk [email protected]
$ talk sarwar@upibm7
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Tracing the Route from One Site to Another Site
traceroute www.yahoo.com
#some administrators disable this cmd for security
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82
Important
Internet
Organizations
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Web Resources
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Web Resources
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Request For Comments (RFCs) – omit it
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The TCP/IP standards are described in a series of
documents, known as the Request for Comments
RFCs are first published as the Internet Drafts
and are made available to all Internet users for
reviewer and feedback by placing them in known
RFC repositories
After the review process is complete, a draft can
become a standard
Some RFCs are for information only others are
experimental
85