T-U

tar

A command, short for Tape ARchive, used to archive all the files together into a single file.

TCP

One of the two standard protocols at the Transport layer of the TCP/IP protocol stack. The other is User Datagram Protocol (UDP). TCP provides connection-oriented, reliable data delivery service.

TCP/IP

A suite of network communications protocols that consists of five layers: Application, Transport, Internet, Network Interface, and Physical. These layers can be mapped to the seven layers of the OSI model.

tmpfs

A memory-based file system that maps the /tmp directory on the hard disk to the memory. As a result, the applications (such as compiler and database management system products) that use the /tmp directory for storing and retrieving their data improve performance.

touch

A command used to create an empty file.

track

Concentric circles on a disk platter to store data.

Transmission Control Protocol

See TCP.

udf

Universal disk format; a format file system used to store information on digital versatile disk or digital video disk (DVD).

UDP

User Datagram Protocol; one of the two standard protocols at the Transport layer of the TCP/IP protocol stack used to provide connectionless, unreliable data delivery service. The other protocol is TCP, which provides connection-oriented, reliable data delivery service.

UFS

UNIX file system; a file system based on the traditional UNIX file system known as the BSD fast file system, the default for Solaris.

ufsboot

The secondary boot program located in the UFS file system on the default boot device. This program, loaded by the primary boot program bootblk, loads the kernel into the memory.

ufsdump

A utility used to hack up files.

ufsrestore

A utility used to restore file systems that are backed up using the ufsdump command.

UID

User ID; the required unique integer associated with a user name. The numbers from 0 to 99 are reserved for system accounts. Regular users should be assigned UIDs from 100 to 60,000, but they can go as high as the largest 32-bit signed positive number: 2147483647.

umask

Defines the permissions on newly created files.

umount

A command used to unmount a mounted file system or a remote resource.

umountall

A command used to unmount all file systems specified in the /etc/vfstab file.

universal disk format

See udf.

UNIX file system

See UFS.

useradd

A command used to create a new user account.

User Datagram Protocol

See UDP.

userdel

A command used to delete a user account from the system.

user ID

See UID.

usermod

A command used to modify existing user accounts.