U

U flag (Linux routing table), The Routing Table
UDP (User Datagram Protocol), A Data Communications Model, User Datagram Protocol
Transport Layer, User Datagram Protocol
udp option (fstab file), The vfstab and fstab files
UID (user ID), The share command, The /etc/exports file, The /etc/exports file
exports file, The /etc/exports file
mapping users to, The /etc/exports file
share command, The share command
uid field (inet.conf file), The Internet Daemon
undefine macro (sendmail), m4 sendmail Macros
unicast addresses, The IP Address
unicast multicast parameter (gated), The isis Statement
Unix, TCP/IP and the Internet, Network Access Layer, The Routing Table, Protocol Numbers, Port Numbers, Port Numbers, Print Services, Using Dynamically Loadable ModulesUsing Dynamically Loadable Modules, The BSD Kernel Configuration File, The options statement, The pseudo-device statement, The device statement, Startup Files, The ifconfig Command, Troubleshooting Serial Connections, Network Information Service, Secure the r CommandsSecure the r Commands, Secure Shell
BSD, The BSD Kernel Configuration File, The options statement, The pseudo-device statement, The device statement
configuration file, The BSD Kernel Configuration File
devices statement, The device statement
options statement, The options statement
pseudo-device statement, The pseudo-device statement
configuration files, startup, Startup Files
dynamically loadable modules, Using Dynamically Loadable ModulesUsing Dynamically Loadable Modules
ifconfig command, overview, The ifconfig Command
lpr command, Print Services
Network Access Layer, Network Access Layer
NIS maps, Network Information Service
port numbers, Port Numbers
protocol numbers, Protocol Numbers
r commands, Secure the r CommandsSecure the r Commands, Secure Shell
disabling, Secure Shell
security considerations, Secure the r CommandsSecure the r Commands
routing tables, The Routing Table
serial ports, troubleshooting, Troubleshooting Serial Connections
services, Port Numbers
TCP/IP and, TCP/IP and the Internet
Unknown host error (ping command), Testing Basic Connectivity
UNKNOWN keyword (security), tcpd access control files
Unreachable Port message, Tracing Routes
UP flag (ifconfig command), Checking the Interface with ifconfig
update (EGP trace option), The egp Statement
update keyword (dbmmanage command), Improved user authentication
UPDATE messages (BGP), Border Gateway Protocol
updates (EGP), Exterior Gateway Protocol
updetach option (pppd), The PPP Daemon
Use field (Linux routing table), The Routing Table, The Routing Table
Use Nice field (sendmail), Defining Mailers
use-host-decl-names parameter (dhcpd), Configuration Parameters
use-id-pool option (named), The options Statement
use-lease-addr-for-default-route parameter (dhcpd), Configuration Parameters
UseCanonicalName directive (httpd.conf file), Basic Configuration Directives
usehostname option (pppd command), PPP Daemon Security, The PPP Daemon
usenet mailer, MAILER
usepeerdns option (pppd), The PPP Daemon
user (sendmail K command value), The sendmail K Command
user authentication, User Authentication (see authentication)
USER command (POP), Post Office Protocol
User Datagram Protocol, A Data Communications Model (see UDP)
User directive (Apache), Managing the Swarm
user option (pppd), The PPP Daemon
user setting (smb.config file), Configuring a Samba Server
USERCTL (Linux configuration value), Assigning an Address
UserDir directive (httpd.conf file), Defining Where Things Are Stored
Userid field (sendmail), Defining Mailers
USERID option (xinetd), Controlling Access with xinetd
use_ct_file (sendmail), FEATURE
use_cw_file (sendmail), FEATURE
UUCP protocol, Simple Mail Transfer Protocol
uucpdomain (sendmail database feature), FEATURE
UUCPSMTP macro (sendmail), m4 sendmail Macros