T-X

TCP/IP (Transmission Control Protocol/Internet Protocol): TCP/IP is a suite of communications protocols for internetwork communication. It is primarily used as the communication system for the Internet.
Telnet: A terminal emulation program that allows you to connect to remote computers. RHEL includes the Kerberos version of the Telnet server, as configured through the /etc/xinetd.d/krb5-telnet configuration file.
tmpwatch: The tmpwatch command removes files that have not been accessed in a specified number of hours. The default daily tmpwatch script checks files in the /tmp and /var/tmp directories.
umask: The umask command defines default permissions for newly created files.
user ID (UID): Every Linux user has a user ID, as defined in /etc/passwd.
usermod: The usermod command modifies different settings in /etc/passwd, such as expiration date and additional groups.
Very Secure FTP (vsFTP): The Very Secure FTP service is the default FTP server for RHEL.
vgcreate: The vgcreate command creates a volume group (VG) from one or more physical volumes (PVs) for Logical Volume Manager (LVM).
vgdisplay: The vgdisplay command specifies current configuration information for volume groups (VGs).
vgextend: The vgextend command allows you to increase the extents or space allocated to a volume group (VG).
vi: The vi editor is a basic Linux text editor. While other editors are more popular, vi may be the only editor you have available in certain rescue environments.
virtual hosts: You can configure multiple Web sites on a single Apache server by configuring a number of virtual hosts in your /etc/httpd/conf/httpd.conf configuration file.
virtualization: Virtualization is an abstraction of computer resources; most often associated with platform virtualization, in which you can include one or more virtual machines on a physical system. Two options for virtualization are VMware and Xen.
VMware: VMware is a proprietary system with virtualization products freely available to all. With snapshots, it can help you test a system with less risk. I've written much of this book with RHEL installed on a VMware Server.
volume group (VG): A collection of physical volumes (PVs) in Logical Volume Manager (LVM).
window manager: The window manager is a special type of X client that controls how other X clients appear on your display.
WINS (Windows Internet Name Service): WINS provides name resolution on Microsoft networks; it can be activated on Samba.
X client: An X client is an application that uses the X server services to display output.
X Display: The X Display is a console and a virtual window. By default, there are six virtual text consoles configured with Linux; the X Display is associated with virtual console number seven.
X server: The X server is the part of the X Window System that runs on your desktop. The X server draws images on your screen, takes input from your keyboard and mouse, and controls access to your display.
X Window System: The GUI for Linux is also known as the X Window. Unlike other applications, the X Window System is a layered application.
Xen: Xen is the native virtualization technology to RHEL. It requires the use of a custom Xen kernel and can support virtual machines in paravirtualized and fully hardware virtualized modes.
xhost: The xhost command can be used to allow other hosts to access your X server. In other words, you can configure remote X clients to send their display to the local X server.
xinetd daemon: The xinetd "super-server" daemon controls connections to servers in the /etc/xinetd.d directory such as the rsync and Kerberos Telnet servers.
X.org: The X.org server is the default X server for RHEL.