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2.2. Overview of Networking

Networks connect computers so that the different systems can share information. For users and system administrators, Unix systems have traditionally provided a set of simple but valuable network services that let you check whether systems are running, refer to files residing on remote systems, communicate via electronic mail, and so on.

For most commands to work over a network, each system must be continuously running a server process in the background, silently waiting to handle the user's request. This kind of process is called a daemon. Common examples, on which you rely for the most basic functions of your Linux system, are named (which translates between numeric IP addresses and more human-readable alphanumeric names), lpd (which sends documents to a printer, possibly over a network), and ftpd (which allows you to connect to another machine via ftp).

Most Unix networking commands are based on Internet protocols. These are standardized ways of communicating across a network on hierarchical layers. The protocols range from addressing and packet routing at a relatively low layer to finding users and executing user commands at a higher layer.

The basic user commands that most systems support over Internet protocols are generally called TCP/IP commands, named after the two most common protocols. You can use all of these commands to communicate with other Unix systems besides Linux systems. Many can also be used to communicate with non-Unix systems, as a wide variety of systems support TCP/IP.

This section also covers NFS and NIS—which allow for transparent file and information sharing across networks—and sendmail.

2.2.1. TCP/IP Administration

ftpd

Server for file transfers.

gated

Manage routing tables between networks.

host

Print host and zone information.

ifconfig

Configure network interface parameters.

named

Translate between domain names and IP addresses.

netstat

Print network status.

nslookup

Query domain name servers.

ping

Check that a remote host is online and responding.

pppd

Create PPP serial connection.

rdate

Notify time server that date has changed.

route

Manage routing tables.

routed

Dynamically keep routing tables up to date.

slattach

Attach serial lines as network interfaces.

sshd

Server for secure shell connections.

telnetd

Server for Telnet sessions from remote hosts.

tftpd

Server for restricted set of file transfers.

2.2.2. NFS and NIS Administration

domainname

Set or display name of current NIS domain.

makedbm

Rebuild NIS databases.

portmap

DARPA port to RPC program number mapper.

rpcinfo

Report RPC information.

ypbind

Connect to NIS server.

ypcat

Print values in NIS database.

ypinit

Build new NIS databases.

ypmatch

Print value of one or more NIS keys.

yppasswd

Change user password in NIS database.

yppasswdd

Update NIS database in response to yppasswd.

yppoll

Determine version of NIS map at NIS server.

yppush

Propagate NIS map.

ypserv

NIS server daemon.

ypset

Point ypbind at a specific server.

yptest

Check NIS configuration.

ypwhich

Display name of NIS server or map master.

ypxfr

Transfer NIS database from server to local host.



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