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UDF (Universal Disk Format)

A file system used for storing information on the optical media technology called DVD (Digital Versatile Disc or Digital Video Disc).

UFS (Unix File System)

The default disk-based file system for the Solaris operating environment.

UFS logging

The process of storing file system operations to a log before the transactions are applied to the file system.


The secondary boot program. It locates and loads the two-part kernel. The kernel consists of a two-piece static core called genunix and unix.

Unbundled software package

A Solaris software package is the standard way to deliver bundled and unbundled software. Packages are administered by using the package administration commands, and they are generally identified by a SUNWxxx naming convention when supplied by Sun Microsystems. SUNW is Sun Microsystems' ticker symbol on the stock exchange, hence the SUNW prefix.


Performed on a system that is already running Solaris 2.6, Solaris 7, Solaris 8, or a previous release of Solaris 9. An upgrade will save as many modifications as possible from the previous version of Solaris that is currently running on your system. See also live upgrade.

User ID (UID)

A unique number assigned to each user account. All UIDs must be consistent across the network. The UID is typically a number between 100 and 60,002, but it can go as high as 2,147,483,647.

User initialization file

A shell initialization file is a shell script that runs automatically each time the user logs in. The initialization file will set up the work environment and customize the shell environment for the user. The primary job of the shell initialization file is to define the user's shell environment, such as the search path, environment variables, and windowing environment.

User mask

Controls the default file permissions assigned to the file or directory.

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