لطفا منتظر باشید ...
When to Run a GUI Access
Server
GUI access servers are most useful when a
computer's primary function is to provide workstation-like functions to
multiple or remote users. For instance, a company with a dozen employees might
purchase one high-powered central system and a dozen much less powerful
computers that function as GUI terminals for the central computer. This central
system could host applications like StarOffice, The GIMP, KMail, and so on. Individuals
would sit at the less-powerful systems, log into the central system, and run
their applications remotely. Compared to an environment in which individuals
sit at workstations that run their programs, this configuration offers several
advantages, including: Central software
administration To add, delete, or upgrade an
application, you need only modify the configuration on a single computer. (For
many applications, an alternative is to use NFS to store applications on a file
server, but run those programs on individual users' workstations.) Simpler workstation
configuration The workstations or other
dedicated systems at which users sit can be very simple, both in terms of
hardware and software. These systems will therefore require little in the way
of routine maintenance and software updates. In some cases, you can handle
these in a centralized manner, as well, if you use some variety of network boot
protocol for the workstations. In fact, you can use a device known as an X terminal, which is
a very simple computer that supports X and has little computing power of its
own. Central hardware
upgrades If new or updated applications need
hardware upgrades, a central server strategy allows you to perform upgrades on
a single system, which can be simpler than upgrading a dozen or more computers.
On the other hand, this also makes your workplace quite vulnerable to failure
of the central system's hardware. This system must also have much more capable
hardware than would any single workstation. Central storage It's usually easier to back up a single system than an entire
network of computers, so this approach can simplify data backups. Depending
upon the client systems you use, they may require no backups, or they could use
simple backups of a default configuration that would probably fit on a single
CD-R. Central user accounts Using a single system permits centralized maintenance of user
accounts. Users may need accounts on only one computer, which can greatly
simplify network configuration. (Depending upon the access terminals' types and
configuration, though, users may need accounts on them, as well.) Users can sit
at any computer, log in, and be greeted by their own desktops and user
preferences. This feature also means that you can easily replace any
individual's computer, since it contains little or nothing in the way of
customizations. Another way to attain this goal is to use a centralized login
server protocol such as Kerberos (described in
Authenticating Users via Kerberos).Of course, a network configured in this way
has its drawbacks, as well. Most importantly, the reliance upon a single
computer means that if that system goes down, all the other computers become
effectively useless. If you decide to configure a network in this way, you
should be particularly diligent about backing up the central system, and have
spare parts on hand in case of a failure. You might even want to configure a
computer as a backup, ready to take over the primary system's duties on a
moment's notice.Even if you aren't configuring a large
network for which you want to use a central system to handle all normal user
logins, you might want to use a GUI login tool to allow smaller-scale or
peer-to-peer logins. All your users might have their own workstations, for
instance, but if they occasionally need to do work from remote locations, those
workstations can be configured to accept remote accesses, allowing a user to
work from another user's workstation, from home, or from some other location.Remote GUI access tools are most often used
on a local network. Because GUI displays transfer a great deal of data, the use
of these protocols across the Internet at large often results in a sluggish
display. Indeed, even on a local network with 100 Mbps hardware, GUI
protocols are noticeably slower than local GUI displays, although the speed on
a local network is usually acceptable. As with text-based remote access tools,
GUI tools provide users with full login privileges, and a password must be
exchanged, so there are security risks to running such protocols. (The VNC
tools encrypt passwords but not regular data, reducing risks slightly. Using
SSH for the initial login allows you to encrypt the password and all session data.)
