Two-Minute Drill

Here are some of the key points from the certification objectives in Chapter 13.

The Extended Internet Services Daemon (xinetd)


xinetd acts as a "super-server" for a number of other network services, such as the Kerberos secured versions of Telnet and rsync.


Individual services have their own management scripts in the /etc/xinetd.d directory.


Most xinetd services are disabled by default.


You can activate an xinetd service with the appropriate chkconfig command or by directly editing its xinetd script.


xinetd listens for connection requests from client applications.


When xinetd receives a connection request, it starts the server associated with the TCP/IP port and then waits for other connection requests.

The Secure Shell Package


The OpenSSH command utilities-sshd, ssh, ssh-keygen, ssh-add, and ssh-agent-provide secure remote services over any network connections.


Encryption is based on private and public keys.


Public keys are shared with others, so that they can communicate with you through SSH.


As it is easy to decipher traffic, even passwords, from telnet, ftp, and the "r" commands, it is best to use SSH on any publicly accessible network.

Dynamic Host Configuration Protocol (DHCP)


DHCP allows a client computer to obtain network information (such as an IP number) from a server.


The BOOTP protocol allows a client computer to access a DHCP server on a remote network.


DHCP servers are configured through /etc/dhcpd.conf.


The DHCP server daemon is dhcpd; the DHCP client daemon is dhclient.

The Network Time Protocol (NTP)


NTP servers can help synchronize the systems on a network.


NTP clients can be configured with the Date/Time Configuration tool, which can be started with the system-config-date command. Alternatively, clients can also be configured in /etc/ntp.conf.


NTP clients can be synchronized with Stratum Two servers with the permission of their administrators; one alternative is the Public Time Server project at


To configure an NTP client as a server, the /etc/ntp.conf file needs to be configured to allow access to the desired networks.

RHCE Red Hat Certified Engineer Linux Study Guide (Exam RH302)
Linux Patch Management: Keeping Linux Systems Up To Date
ISBN: 0132366754
EAN: 2147483647
Year: 2004
Pages: 227
Authors: Michael Jang © 2008-2017.
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