UDP --
User Datagram Protocol, a protocol at the same layer as
TCP, but without acknowledgment of transmission
and therefore unreliable.
UFS --
The Unified FileSystem, a derivative
of the 4.2 BSD file system. It offers file
hardening, supports large and fragmented block allocations for
files, and distributed inode and free block management.
Additionally, it supports quotas.
ulimit --
A value that limits the maximum file size that can be created on
the system.
umask --
A permissions
mask
that controls the
permissions
assigned to new
files
you create.
You can set your
umask(2)
from the
command line
or in one of
your
shell
startup files.
universal address --
(programming)
A machine-independent representation of a network address.
UNIX --
An operating system originally developed at Bell Laboratories, after
which several different versions were developed. UNIX supports
multiuser and multitasking operation and provides software tools
that make it advantageous as an environment for software
development.
UNIX command line --
A line in a UNIX window on which you can enter commands
to communicate with the UNIX operating system.
UNIX mode --
By installing a filesystem on a NetWare server in UNIX mode, the filesystem
supports the semantics of a normal UNIX filesystem when you access it.
For example, you can use chown and chmod to change file
permissions, and you can use filenames that are case-sensitive and longer than
the standard 8.3 character file naming convention used by DOS.
emini).
unsharing --
Making a shared local resource unavailable to remote systems.
upgrade installation --
A nondestructive installation where one release of the operating
system replaces an earlier release. Upgrade installations preserve user data.
upstream --
(programming)
In a stream, the direction from driver to stream head.
URL --
Uniform Resource Locator.
This is a network extension to the
standard filename concept. Not only can you
point to a file in a directory,
but that file and that directory can exist
on any machine accessible via your network.
URLs can point to queries, documents stored
within databases, or the results
of other types of commands. For example:
http: //systemname.caldera.com/filename.html
In this example, http: signifies how to get a document, systemname.caldera.com signifies where to get it, and filename.html signifies what to get.
user --
Any person who interacts directly with a computer system.
user account --
The records a UNIX system keeps for each user on the
system.
user ID --
(programming)
A user ID is an integer value, usually
associated with a login name, that the system uses
to identify owners of files and directories.
The user ID of a process becomes the owner
of files created by the process
and by descendent processes. See also
fork(2).
user name --
The name by which a user is known in a UNIX operating system.
user space --
(programming)
The part of the
operating system
where programs that do not have
direct access to the kernel structures and services execute.
The UNIX operating system
is divided into two major areas: the user program and the
kernel.
Drivers execute in the kernel,
and the user programs that interact with
drivers generally execute in the user program area.
This space is also referred to as user data area.
utility --
1. A program that is part of the operating system.
2. (programming) A software tool of general programming usefulness
built-in to FMLI,
such as fmlgrep or message
which can be used inside backquoted expressions, and which is
executed when the
backquoted expression
is evaluated.
A built-in utility has a performance advantage over a shell
utility in that it does not fork a new process.
UUCP (UNIX-to-UNIX Copy) --
The group of networking commands and protocols used to transfer files, do
remote execution, and log in to remote systems. This is the original UNIX
system networking package and is used primarily today for serial
communications (modem and direct connections).