Linux Network Services

You can activate many basic networks services on a Linux computer. Several are controlled by the xinetd daemon. Many administrators set up their own DNS servers so they don t have to maintain /etc/ hosts on every computer on their networks. Others set up their own DHCP servers; this frees them from having to maintain IP address information on every computer on their networks. Commands are also available to help you set up and configure printers, as well as configure the sendmail server.

This section addresses just the commands that you might run at the command-line interface; no GUI tools are discussed. For more information on the services in this section, refer to Chapters 23 26 .

Commands for xinetd Services

As we mentioned, many services, including the Remote Shell and Telnet, are controlled through the Extended Internet Services Daemon, xinetd . This daemon listens for requests and starts network services on demand.

You can start the Remote Shell from a client using a number of different commands, which appear in Table A.24.

Table A.24: Remote Shell Commands

Command

Description

rlogin     hostname

Logs into a remote computer with a Remote Shell server; uses the current username.

rlogin -l username hostname

Logs into the remote hostname computer with a different username .

rsh hostname

Logs into a remote computer with a Remote Shell server; uses the current username.

rsh -l username hostname

Logs into the remote hostname computer with a different username .

rexec hostname command

Logs into the remote computer hostname and executes the command .

Variations on the telnet command are quite rich, but many cover very special situations. Since telnet provides a straightforward remote login interface, not many variations are required. A few useful options are shown in Table A.25.

Table A.25: telnet Commands

Command

Description

telnet hostname

Opens a console login interface on hostname .

telnet -a hostname

Sends the current USER as the username for the telnet login process.

telnet -f hostname

Supports the use of Kerberos on the Telnet server.

telnet -l username hostname

Attempts to log into the hostname computer as username .

DNS and DHCP

There aren t a lot of commands related to the DNS or DHCP servers or clients . Chapter 24 explains the configuration of these systems; the commands in their main configuration files, /etc/named.conf and /etc/dhcpd.conf , are addressed in detail in that chapter. Table A.26 describes a few basic commands.

Table A.26: DNS and DHCP Commands

Command

Description

named

DNS server daemon.

dhcpd

DHCP server daemon.

dhclient

DHCP client daemon; can also be used as a command to refresh IP address data. In previous Red Hat distributions, this command was called dhcpcd or pump .

Printer Commands

Associated with the CUPS and LPD print systems are several basic commands, some of which apply to both systems. For example, with the cups-lpd service, which is part of xinetd , LPD commands are automatically translated for a CUPS system. Basic print commands are described in Table A.27.

Table A.27: Basic Print Commands

Command

Description

lpr file

Prints the file; this is the basic LPD print command.

lpc

Manages LPD print queues and active printers.

lpq

Examines the print spool; you can specify the printer with the -P switch.

lprm job

Removes a print job with job number.

cupsaddsmb

Allows you to share a CUPS printer via Samba.

cupsconfig

Opens the CUPS configuration utility in the Lynx text browser.

cups-lpd

Starts the CUPS LPD xinetd service that allows CUPS to read LPD commands.

filter

Adds a new CUPS filter.

lp file

Prints the file using CUPS.

lppasswd

Controls access to the CUPS configuration.

lpoptions

Sets CUPS printer options/defaults.

lpstatus

Prints CUPS status (queue) information.

Mail Management Commands

Linux offers commands that help you manage the sendmail mail server. The most important of these commands, the m4 macro processor, just processes the sendmail configuration file. Other commands allow you to manage aliases, databases, and more. These commands are described in Table A.28. For more information on sendmail, read Chapter 26 .

Table A.28: sendmail Commands

Command

Description

m4

Processes the sendmail macro file, normally /etc/mail/sendmail.mc, into a format suitable for the sendmail configuration file, normally /etc/mail/sendmail.cf .

mailq

Sends a summary of queued mail message headers to the printer; sendmail -bp performs the same task.

makemap

Creates sendmail database maps from /etc/mail configuration files.

mailstats

Returns mail statistics ” numbers of messages, total sizes, and more.

newaliases

When you change /etc/aliases , this command updates the sendmail database.

praliases

Shows current aliases from the database.

rmail

Reads UUCP-based mail.

smrsh

Enters the sendmail shell.

 


Mastering Red Hat Linux 9
Building Tablet PC Applications (Pro-Developer)
ISBN: 078214179X
EAN: 2147483647
Year: 2005
Pages: 220

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