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Unit [01] Network Overview
- Unit Objectives:
- Identify the types of networks and state the features of each
- State the features of the Internet
- Describe the network address and network naming conventions
- State the purpose of network protocols
- Identify and state the purpose of a gateway
- Name the protocols used with the TCP/IP network model and state the purpose of each
- Define and state the purpose of the network file system
- Network environments provide several advantages over individual computers:
- Data can be shared
- Expensive hardware can be shared
- Software can be shared
- Multiple users can share resources
- Network categories: WAN wide area networks, MAN metropolitan area networks,
LAN local area networks.
- The Internet is a large, worldwide network consisting of numerous individual
networks, each with many individual host computers and lots of users. The individual networks are usually assigned to Internet group according to geographical location.
- Domain Name Service: provides access to hosts on the Internet without requiring the user to know
intermediate domain names. Name servers maintain the lists of registered those. Resolvers provide routing information for registered hosts. Normally, there are only a few DNS within a network topography
and the resolvers use these DNS's to obtain routing information.
- IP Address are used to identify hosts on the Internet. The addresses consist of four eight-bit integers
separated by dots. There three main classes of Internet addresses and Dan IP address consist of both the network address and the host address. Depending on the class of network address, the size above
the network part and host part of the IP address will differ.
- Class A Network Address consist of an 8-bit network address and a 24-bit host address. The
network address must be less than 128. Example 98.0.0.34 reads host 34 on network 98
- Class B Network Address consists of a 16-bit network address and a 16-bit host address. The
network address must be greater than 128. Example 176.27.0.33 hosts 33 on network 176.27
- Class C Network Address consist of a 24-bit network address and an 8-bit host address. The
network address must be greater than 191 Example 201.16.12.45 host 45 on network 201.16.12.45
- Reserved Numbers have special meeting when used in a network address.
- 0 reserved for systems which do not know their Internet address
- 127 reserved for loopback facilities
- 255 reserved for broadcast messages
- Network names provide a means of symbolically referencing the Internet address for a network or host.
This makes it much easier to use networking software to access remote systems. Each system on a network is assigned a host name. The host name does not have the register and with the NIC.
- Network Terminology: Protocol provides a formal set of rules by which data communications will be
performed. Each layer of the network has its own set of protocol. Layers defines the data communication function performed by a protocol. For example, TCP is a layer which implements the transmission control
protocol. Peer refers to the same protocol layer on a remote system. Interface pro lives in arrangement
as to how data will be passed between two layers. A layer may contain multiple protocols, each protocol communicates with its peer, each layer knows only about the layer immediately above and below itself.
- Gateways are host computers which provide a connection between two or more different networks. A
network is considered different if either the physical communications media differs and the network address differs. Each network host is assigned a unique IP address, consisting of four numbers separated
by a dot. The first part of the IP address defines the network. If the network address is the same for both the sending hosts and receiving hosts, both hosts are considered to be on the same network. On a
local network all hosts on the network have the same network address.
- Packets are routed between network computers. The packet may consist of data or header or
information. Each layer in the protocol stack adds a header to the beginning of the packet before passing
the packet to the next layer. The header contains control and routing information for the receiving layer. When a packet is sent over the network and is received by the destination host each layer reads the
header and takes one of several actions. If the data is destined for the receiving layer, the data is processed according to the instructions contained in the header. If the data is destined for a higher
level, the header is re-grooved and the packet is passed onto the next layer.
- ISO/OSI Network Model, open system interconnection produced by the international standards
organization consists of seven distinct layers of software and hardware. At the bottom layer, the model specifies how the hardware passes bids of information across the network. At the higher layers, and the
user services such as reliability, security, and data presentation or specified. The implementation such as TCP/IP to not follow the ISO/OSI model exactly, but do adhere to the theoretical model.
- Application layer provides and users services for exchange of information, such as male, remote
login are remote file transfer
- Presentation layer provides for presentation of information to the user in a meaningful form.
Including data compression and decompression, encryption and character translation
- Session layer, provides for the coordination of communications and connections of applications.
This level for lies remote terminal services.
- Transport layer is responsible for the reliable transmission of data between systems
- Network layer provides for the routing of data to a system on a local area network. This layer
isolates the higher layers from the underlying network and provides addressing and delivery data
- Data link layer provides for the reliable delivery of data across the physical network. The
protocols at this layer guarantee he that the data has been delivered, but do not guarantee that the destination system excepted data are was able to route it.
- Physical layer provides the physical connection between two systems and defines the
characteristics to transmit and received data. This includes voltage and current specifications
- TCP/IP Features
- TCP Transmission Control Protocol provides reliable data delivery service with error detection and error correction facilities
- IP Internet Protocol provides the basic packet delivery services on which the TCP/IP networks are
built. All data between network computers flows through IP. Together TCP/IP pro line open protocol standards which can be adopted on virtually any hardware running any operating system,
independence from specific physical network hardware and can run on many network topography or network hardware. It also provides the standard addressing scheme allowing data to be sent to and
received from network devices. There are useful standardize user services, such as remote terminal, file transfer, and electronic mail.
- TCP/IP Services are defined as user services and network services
- User Services include electronic mail, remote terminal services, file transfer or services, remote
command execution
- Network Services include domain name service, network file systems, UUCP over TCP/IP, SNMP, SL
IP, PPP, NetBIOS
- TCP/IP Protocol Suite as for software layers build on an underlying hardware layer. The TCP/IP model
contains all the functionality of the ISO/OSI model with fewer layers.
- Application Layer provides communication between application programs. This layer incorporates
the OSI presentation, session, and application layers. The application layer uses three main protocols
- FTP used to transfer files between two systems
- Telnet provides remote terminal facilities
- SMTP provides electronic mail delivery
- additional services available on most Unix systems include; rlogin, rcp, finger, rwho
- Transport Layer provides end to end delivery service. There are two methods which can be used:
Transmission Control Protocol delivery which provides reliability checks, or Datagram Protocol which does not provide reliability checks
- TCP provides reliable data transmission and reception. Normally, application programs use TCP
to ensure that the data sent and received intact. TCP includes the following features: virtual circuit connection went to applications wish to exchange data they "virtual circuit" is
established between the TCP layer above hosts. During the transmission of data, the TCP's also exchange control information that indicate that the data is being received correctly. It
data is received incorrectly, the sending TCP will retransmit the packet. Full duplex connection provides for the flow of information in both directions between the two TCP layers. Unstructured data
the TCP on the sender breaks the data into smaller blocks packets and sends it to the receiver or the data is reassembled. TCP is responsible for re-assembling
the packets containing the data received. The header contains information on how the data is to be reassembled. Buffered data transfer TCP gathers data from applications into buffers
and then sends the data with a buffer is full.
- UDP also delivers data to another system, and is used for delivery of small amounts of data
for which the delivery does not have to be guaranteed.
- Internet Layer uses the Internet Protocol to deliver data and he Internet Control Messages
Protocol for control.
- The Internet layer Internet protocol implements the datagram "packet" format as determined
by the underlying physical network. It also implements the Internet address "provides for the mapping of Internet address to physical device address", routes data between the network
access layer and transport layer, routes data between two hosts on a local network are to a gateway hosts if the data is destined for a host on a remote network, fragments and
reassembled packets as required by the lower-level protocols "network access layer"
- The Internet layer ICMP processes error and advisory messages, sends and receives flow
control information, reports errors and other information necessary to ensure reliable communications. The echo request/echo reply message are sent between two hosts to check
the status of the communication path. The ping command performs this task. Destination under reachable our messages sent by Gateway systems to indicate that a foreign network
cannot be reached. Source quench message indicates that there are is a flow control problem. Redirect message is sent by a gateway to inform the sender that there is a better route by which to send data.
- Network Access Layer excepts and transmits data over the network. This layer provides the
functionality of the three lower layers of the OSI model: network, data link, and physical. Since the TCP/IP protocol sits on top of the network access layer the actual implementation of how to access
the physical network is removed from the user. On any one hardware system, there may be multiple network access layers to support multiple physical network communication media's. The systems are called gateways.
- IP Data Routing provides for the routing of data between two hosts. Both hosts could be on the same
network or in each hosts can be on a different network. If the hosts are on different networks, then the data must be routed through a gateway.
- Network File Systems provide the capability of sharing file systems (normally, directory structures on a
remote system) between systems on the network. Users on the local system can access files on a network file in the same manner as if the file was on the local machine. Network file systems are set up
by the remote systemexporting the names of directory structures which it will allow other systems to access, the local system mounts the remote system directory in a manner similar to mounting local physical file systems.
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Unit [02] Network Commands
- Unit Objectives
- Use the network remote terminal command telnet and rlogin
- Use the remote execution command rcmp
- Use the file transfer commands ftp and rcp
- Use network remote user information commands rwho and finger
- Use the network status commands ping, ruptime, and netstat
- Remote Terminal Servers telnet command uses the telnet protocol to provied remote terminal services
between two hosts on a network. If Telnet is invoked without the name of the remote hosts, Telnet will enter command mode.
- Remote Login rlogin allows users to remotely log in on another host on a network, provided the user has
an account on the remote system. The user ID for the user is automatically sent to remote system. Rlogin has the advantage over Telnet in that the user does not have to enter their log-in ID and possibly
their password. Rlogin also sends the terminal type as specified in the term variable on the local system, to the remote system.
- $HOME/.rhosts can contain the name of remote systems and users on remote systems wich the user on
the local system wants to allow access to their account.
- Remote Shell rsh command allows the user with proper permissions, to execute and command on a
remote system. Interrupt, quit, and terminate signals received by rsh are also received by the remote command; rsh normally terminates at the same time as a remote command. By default, the command
belongs to the user on the remote host of the same name as the user who ran the rsh. this means that the resulting processes belonging to the remote user and begin with the remote users home directory as
his or her working directory. Options permit you to specify another user on the remote host as the owner. Either way, the remote system must have declared the local user equivalent to the remote user in the
/etc/hosts.equiv or .rhost file in the current directory of the target user.
- File Transfer Protocol ftp command allows you to transfer files from one machine to another. The
operating system on the two machines may be different. ftp is that interactive command which requires you to log-in. ftp is an interactive program which has its own set of commands build into it. ftp file
naming conventions include many rules. If the filename "--" is specified the standard input for reading or standard output for writing is used. if the first character of the filename is "|" the remainder of the
argument is interpreted as a shell command. ftp then forks a shell. ftp file types include ASCII text, bianary data, and tenex files.
- Executing Unix Commands on the Local System: The shell escape
( ! ) can be used at the FTP prompt to execute a command on the local system. After the command is executed, the user is returned
to the FTP prompt. Example: ftp> !date If you want to execute more than 1 or 2 Unix commands on the local machine, you can start a shell on the local system, perform your task, then Cntrl-D back to the FTP
prompt. Example: ftp> !ksh
- FTP File Naming Conventions: A filename of - will tell the FTP command to read from stdin or write to
stdout. A | is used like a pipe. Commands containing spaces must be quoted. If the first character of the filename is "|" the remainder of the argument is interpreted as a shell command. FTP than forks a
shell and reads from the stdin or writes to stdout. If the shell command includes spaces, the arguments must be quoted. Example: "| ls -lt" dir | more. The glob command allows filename expansion using shell
metacharacters for commands which except multiple filenames. If globbing is enabled, local filenames are expanded according to the rules used by the shell.
- FTP File Types: ASCII, binary, tenex.
- FTP File Commands:
- type ftye set the file transfer type
- verbose toggle response from remote host
- hash print hash marks "#" after each 4096 bytes transferred
- File Transfer Local to Remote the put
command is used to transfer a single file for local system to the remote system. The put command can be used interactively, in which case the user will be prompted for both the local filename and the remote filename. The
get command is used to transfer a single file from remote system to the local system. To transfer multiple files used the mget command, mput command , glob, and the prompt command.
- FTP Auto Login The .netrc file located in the users home directory on the local system, contains login
and initialization information used by the FTP auto login process. This file contains the names of remote systems, login names, passwords, and account information. When FTP is invoked, it checks to see if a
user has a .netrc file in their home directory. If so that information is used to logon the remote system. Do not use this arrangement, it is the famous security hole. Some programs search file structures for
.netrc files and alerts the system administrator of their existence, so appropriate action may be taken.
- Ftp Control Files: Two files to restrict access to ftp
- /etc/ftpusers contains a list of users for which ftp service is to be denied. This file is checked
upon each ftp connection. It is suggested that the file contain at least the uucp and root login names.
- /etc/shells FTP expects the user to be assigned the /bin/sh shell by default. If a user is assigned
a different shell in the /etc/passwd file, the name of this shell should be entered into the /etc/shells file, otherwise, FTP will not allow the user to log in.
- The rcp - Remote Copy Command allows you to copy files for one machine on the network to another
machine is useful for transferring small numbers of files across the network.
- The rwho - Remote Who Command
provides a list of users currently logged in two local system and remote system on the network which are providing rwho status. The rwho command displays the user's
name, the systems name and terminal port, date and time the user login, idle time.
- The ruptime - Remote System Status command displays the status of all systems on the network. The
/usr/sbin/in.rwhod daemon must be running in order for remote systems to report their status. The ruptime command displays the following information; system name, system state, length of time the
system has been in this state, number of users currently logged on, average number of processes in the last 1.5, and 15 minutes.
- The finger Command: allows a user to obtain information about users log in to the local and remote
systems on the network. Each user can create two files in their home directory to provide information about themselves:
- $HOME/.plan file contains information about the users current plan.
- $HOME/.project file contains one line of information about the users current project.
- The ping Command checks if another host can communicate with the local host.
- The netstat Command displays the content of various network-related data structures. It is useful for
network administrators to get a snap-shot of the health of the network
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Unit [03] Network Hardware
- Unit Objectives
- Define the common types of ethernet hardware connections
- State the characteristics of each type of ethernet networks
- Identify the hardware required to connect ethernet devices to
each type of ethernet network
- Identify ethernet hardware addressing scheme
- Ethernet Networks implement the local area network specifications on a "bus" topology. All systems on
ethernet share the same communication media. Data on ethernet can be transmitted very fast, usually in the 10 Mb region. Ethernet's use broadcast technology. All hosts on the ethernet receive all packets.
He chose must determine which packets are for it.
- Ethernet Hardware each device on the ethernet (hosts, printer, etc.) must have a network interface
card installed in which provides the connections to interface to the selected media. Network cards are available from numerous manufacturers, but they all provide to basic types of interfaces: NAU network
access unit network card provides interface to the 10-base T type communications media. A "hub" is required in order to interface the card to the network. EN coaxial connector. The Network Hub
provides for the routing of data to the various network devices.
- Ethernet Communications CSMA/D Access
collision sense multiple access with collision detection. When a system is transmitting it uses carrier signals to inform other transceivers of message traffic.
What a system is ready to transmit, the first monitors the ethernet cable for carrier sense. If it senses a signal because some other system is transmitting, the system will continue monitoring until the network is
clear. Collisions occurr when two or more systems try to transmit at the same time. When a collision occurs all systems on the network stop transmitting, each system waits a random amount of time, when
time expires the system begins to monitor the network attempting to retransmit. Thirty percent network traffic is considered maximum on a 10-base T configuration.
- Ethernet Hardware Addresses each system on ethernet has two addresses: an IP address (software),
and a unique hardware address. The IP address is mapped to the hardware address when the network is started. Ethernet hardware address consists of 48 bits. Each ethernet hardware address is guaranteed
to be unique because each ethernet hardware vendor has a set of addresses assigned to them. The IEEE assigns the first 24 bits in the hardware manufacturer uses the last 24 bits to construct a unique
hardware address. This is important because collisions may occur if two or more hardware devices have the same ethernet address. Each host on the ethernet listens for packets addressed to it. The network
card can also accept two additional addresses. Broadcast addresses is used to send a message to all systems on the ethernet. The broadcast address is all 1's. Multicast address provides the limited form of
the broadcast and is normally used to send a message to a subset of hosts on the ethernet. Never change in ethernet interfaces hardware address, spoofing is a bad thing.
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Unit [04] Network Administration
- Unit Objectives
- Identify the network daemons and state the purpose of each
- Identify the network control files and state the purpose of each
- Describe the start-up and shutdown processes for the network software daemons
- State the purpose of the ifconfig command and how it is used to initialize and modify a network interface
- State the purpose of the netstat command and use it to determine network statistics
- Network Daemons and Sockets
- Daemons are processes which run in the background. Network daemons listen for incoming
network service requests. When a service requests is received, the network daemon process may handle the request directly or it may start-up another process to handle the request. Durring
system startup, various networking daemons are started to handle the incoming and outgoing TCP/IP requests. On newer versions of Unix, a single inetd is started to handle all of the network
requests. This daemon listens to the network and when a server's request is received, inetd starts the appropriate service daemon.
- Sockets is not a true physical connection; rather a socket is a virtual connection managed by the
networking software. Each service is assigned a socket number in the /etc/services file. When an incoming or outgoing service is established, that service will use the socket assigned to it.
Normally, most of the network services are assigned to a predetermined socket number and this socket number should not be arbitrarily changed. In some documentation the term port is used instead of socket.
- inetd Daemon often called the "Super-Daemon
". Listens on multiple ports for incoming connection requests. When a request is received, it starts the appropriate server. This allows other services to be
spawned only when needed and to terminate when they have satisfied a particular request. The following servers may be started by inetd:
- fingerd finger daemon
- ftpd file transfer daemon
- rexecd remote command execution daemon
- rlogind remote login daemon
- rshd remote shell daemona
- talkd talke daemon
- telnetd telnet daemon
- tftpd trivial file transfer daemon
- inetd is started when the system enters run-level 2 by the
/etc/rc2.d/S72inetsvc start-up script, to obtain information about the services spawned, inetd reads the /etc/inetd.config configuration file. (Note that the /etc/services and /etc/protocols
files must also be properly configured) inetd then creates a socket for each service and binds the socket to the port specified in the /etc/services file for that service. inetd
then issues a listen system call on each socket and waits for incoming connection request. Once the service has completed the port is free and the service dies.
- Connection Request there are two types of incoming service requests:
connections and datagrams. inetd services both types of requests, but in a slightly different manner.
- Connection Requests is received on a listening socket,
inetd issues an accept system call, thereby creating a new socket. inetd starts up the appropriate service, passing any program arguments that are specified in the configuration file. Then inetd
continues to listen to the original socket for the request. The invoked service has I/O to stdin, stdout, stderr associated with the new socket; this connects the server to the client process.
- Datagram Request when data is waiting on a datagram socket,
inetd starts the appropriate service, passing it in the service program arguments. Unlike a connection based service, a datagram service has I/O to stdin, stdout, stderr
associated with the original socket. If the datagram socket is marked as wait, the invoked server must process the message before the socket
is made available for the new connection. If the datagram socket is marked as nowait, inetd continues to process incoming messages on that port.
- Optional Services Daemons may be started upon system startup, depending on whether or not the
system administrator determines that the services are required. The services may be started by /etc/rc2.d/ invocation of listed scripts depending upon system configuration.
- in.routed Network Routing Daemon. This service updates the local systems internal routing tables.
- in.named Domain Name Service Daemon. This daemon is used if the local host is a domain name
server. If the system uses a /etc/hosts file for host information are the local system is a resolver, then this service should not be started.
- in.rarpd Reverse Address Resolution Daemon.
- Network Control Files There are several files which provided information to the network service daemon.
These files are maintained by the system administrator and a formatted these files is very important.
- /etc/host This file contains the IP address and the name of each host with which the local host
communicates.
- /etc/networks This file contains the network number and name of the networks the local host has
access to.
- /etc/protocols This file contains information about the various protocols used by the TCP/IP
services.
- /etc/services This file contains information on the services available to the TCP/IP software.
Each line in this file contains two or more fields specifying the name of the service, service number/protocol name, and optional aliases.
- /etc/hosts.equiv (Optional) This file contains the names of hosts which the local hosts considers
to be trusted.
- /etc/hosts.lpd (Optional) This file contains a list of remote host which can access to local hosts
line printing facilities.
- /etc/inetd.conf This file contains information used to configure the
inetd daemon and is used upon start-up and whenever a hangup signal is received. When a request is received the inetd examines
the entries in this file to determine which service is to be started. Each line in the file contains information about a specific service. Each line has several fields separated by spaces or tabs.
- service the name of the service. The service name must also be listed in the
/etc/services file.
- socket_type this entry is either stream
, indicating a TCP pace service, or dgram, indicating a UDP based service.
- protocol the protocol type, either tcp or
udp
- wait/nowait this field applies to the incoming service requests.
wait is used with single-threaded datagram services which process all incoming datagrams on a socket and eventually time-out. nowait services free the socket so that further incoming service
request to that socket are received.
- user The name of the user ID which is to be used to execute the service. This name must be
contained in the /etc/passwd file.
- server This field specifies the full pathname of the server program which is to be executed by
inetd
- args These programs are passed to the service program upon start-up. The first argument in
the list should be the name of the program to be executed.
- Network Start-up the network daemons are started when the system enters run-level 2. There are
three main shell scripts which configure the hardware and start-up the various network daemons depending upon system configuration.
- /etc/rcS.d/S30rootusr.sh
- Configure software loopback driver
- Configure network hardware interfaces
- Sets hostname
- Sets up the routing tables
- Performs preliminary configuration of NFS
- /etc/rc2/d/S69inet
- Configures IP routing
- Sets up NIS domain name (if using NIS)
- Starts appropriate routing daemons
- /etc/rc2.d/S72inetsvc
- Starts of name service daemon (if using DNS)
- Ads static routing information
- Starts the /usr/sbin/inetd daemon
- The ifconfig Command is used to assign an address to a network interface and to configure network
interface parameters. During system startup the ifconfig is called to define the network address of each interface present on a machine. ifconfig
can also be used to redefine and interfaces addressed or other operating parameter, or to display the current configuration of the interface. The interface parameter is a string of the form name unit, for example "le0".
ifconfig is called from the /etc/rcS.d/S30rootusr.sh. There are many parameters associated with this command.
- Using The ifconfig Command is usually used within the network startup script to configure network
interfaces when the system is rooted. However, the system administrator may use the ifconfig command to obtain status information about configure network interfaces or modify existing interfaces. Executing the
ifconfig -a command will show the status of all configured interfaces. netstat -r or netstat -i commands can be used to ascertain the names of configured interfaces. The configuration of a network
interface should not be changed unless you know exactly what you're doing.
- netstat Command displays the contents of various network-related data structures. And presents the
number of display formats, depending upon the options specified when invoked. The default display, for active sockets, shows the local and remote addresses, send and receive huge size, protocol. The
interface display provides a table of cumulative statistics regarding packets transferred, errors in collisions. The routing table display indicates the available routes and the status. Each route consist of
the destination host or network and Gateway to use in forwarding the packets.
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Unit [05] Remote Line Printing
- Unit Objectives
- Install remote line printer facilities
- Configure remote line print services on a local Unix system
- Configure remote line print services on a remote Unix system
- Test and verify correct operation of remote line print services
- Why Use Remote Line Printing
- active connections
- configured interfaces
- routing tables
- network statistics
- SREAMS buffer allocation errors
- packet traffic
- Setting up the Local Printer any printer which is physically connected to local system may be used to
provide rewrote print services. A local printer is configured using the /usr/lib/lpadmin or admintool under Open Windows. Remember, as far as the remote system is concerned, it will simply send the job to
local system which will route it to the specified printer.
- /etc/hosts.equiv /etc/hosts.lpd Files in order for remote line printing to work, the remote system's
name must be contained in neither the /etc/hosts.equiv /etc/hosts.lpd files on the local system. Most systems usually use the /etc/hosts.lpd file to provide better security.
- lpsystem Command can be used to add, delete, and/or list entries contained in the /etc/lp/Systems
file. Example, use the lpsystem Command to list all of the system printer access enteries contained in the /etc/lp/Systems file.
- Configuring Local Printer the printer must be defined on the remote system which will route print jobs to
a local system. The /usr/lib/lpadmin command is used setup and configure a remote printer. The remote system must know the name of the printer on the remote system, the name of the system the
printer is physically connected to, the name of the printer on the system to which it is connected. Ensure lpd daemon is running.
- Troubleshooting Remote Line Printers
- Insure local printer is operating correctly
- Insure that the service access controller is running
- Insure that the port monitors for the print services are configured correctly and are running
- Insure remote systems are entered into the local system's /etc/hosts.equiv or /etc/hosts.lpd Files
- Insure that the entery for the remote system is correct in the /etc/lp/Systems file on the local system.
- Ensure that the /usr/lib/lpsched daemon is running.
Unit [06] Network File Systems
- Unit Objectives
- Networks allow remote machines to have access to data on other machines. The TCP/IP software
supports such data access to a facility known as the Network File System. The NFS fits into the application layer of the TCP/IP. Therefore, NFS can be used between many different types of
systems, as long as the systems support TCP/IP.
- Describe the Network File System facilities and state the steps for setting up NFS on a server and
client. The system administrator on one system can make selected system resources available to other systems on the network. System administrators on another machine can then use these
resources as if they were on their system.
- The system which allows other systems to use its resources is commonly called the server.
- Systems which use server resources are called clients.
- Server systems make resources available to clients by sharing resources.
- Clients use server resources by mounting their resources.
- Setup an NFS server
- Setup an NFS client
- Remotely mount network file systems
- NFS Daemons in order to run the network file system, there must be several daemons running on both
the server and client system.
- lockd daemon processes request to lock portions of files over NFS
- statd daemon processes NFS status request
- mountd daemon services NFS mount requests on both the client and server systems.
- nfsd daemon is used on the server system to start a specified number of NFS demons that process
client NFS access requests. The number of demons started is based on the load expected on the server.
- Filesystem Sharing and Exporting before a remote system can have access to a local system
filesystem resources, the local system must tell the remote system which resources are available for access. This process is called sharing and this sometimes called exporting. Regardless of the
terminology, the end results are the same: a local systems filesystem resources are made available to remote system for mounting.
- NFS Commands and Files there are two commands, one on the server, and one on the client which are
required to set up NFS.
- /usr/sbin/share command makes network file systems resources available to remote systems.
Not only can the share command make a filesystem available to a remote system, but there are several options which control how and by whom the local filesystem can be accessed.
- /usr/sbin/unshare make a shared resource unavailable.
- /usr/bin/shareall share multiple resources
- /etc/mount command is used to make remote resources available to the client system by
"mounting" the resource onto the local directory.
- /etc/dfs/dfstab contains a list of server resources which are to be made available to NFS clients
during boot or when the /usr/sbin/exportfs command is used. This file gives the system administrator a uniform method of controlling the automatic sharing of local resources.
- Setting up NFS Server
- Ensure that the NFS daemons were running on the server system. Example ps -elf |grep nfsd
- Determine the resources which are to be made available to client systems. Example /etc/exportfs /u/local
- Share the resources using the share command or by creating entries in the /etc/dfs/dfstab file. Example
share -F nfs -d "/u filesystem" /u
- Setting up NFS Client
- Ensure that the NFS client daemons are running on the client system
- Create directory on which NFS resources are to be mounted. Example mkdir /u/local
- Mount the remote resource on the directory using the mount command. Example /etc/mount -F nfs system1:/u/local /u/
- Removing NFS Resources
- Unmount resources on client
- Unshare server resources
- Remove resources from /etc/dfs/dfstab file
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Unit [07] Unix Installation
- Unit Objectives
- Analyze installation requirements
- Determine installation options
- Perform the complete installation of the operating system
- Install selected application packages
- Unix System Installation may be needed for a number of reasons;
including, the system is new and has never had Unix install before, a system with Unix cannot be booted, the system needs to be reconfigured (i.e., changes to size of filesystem, swap areas, additional memory added, etc.)
- Full installation installs a complete operating system.
- Partial installation installs only certain packages or restore is missing files. After a full installation
you'll have to configure the network, add printers and terminals, set up user accounts, and install additional application software packages.
- Before you begin insure that you know what is going on. Things you must know: log book
up-to-date, current full backup of all file systems, network information, hardware information, terminal configurations, printer setup, system configuration files, user accounts, groups, NFS/remote
line printing, cron jobs, application software.
- Analyze Installation Requirements
- Swap Space requirements, the amount of RAM normally determines the minimum amount of swap
space. Usually, swap space is set to 1.5 - 2.0 times the amount of RAM
- Root File systems space. The entire distribution requires approximately 331 MB of disk space.
You should allow for an additional 15 percent of free space.
- Additional File systems System Administrators Create Separate File Systems for the /usr, /tmp,
and user home directory structures. However, be careful not to create too many small while systems as you will find these are hard to manage and waste space.
- Determine additional space requirements. Plan system growth.
- Determine the type of Name Service your system will be using. The system can use NIS+, NIS,
DNS or stand-alone using the /etc/hosts.
- System Installation Task
- Install operating system
- Restore user data from backup media
- Configure network and name service
- Install printers, terminals and modems
- Install additional packages
- Additional installation task as necessary
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