The Virtualization Cookbook for SLES 10 SP2 - z/VM - IBM

► Rerun the same scp commands:
# time scp -c 3des-cbc /tmp/testdata.txt localhost:/dev/null
Password:
testdata.txt 100% 200MB 66.7MB/s 00:03
real 0m5.890s
user 0m1.542s
sys 0m0.558s
# time scp -c aes128-cbc /tmp/testdata.txt localhost:/dev/null
Password:
testdata.txt 100% 200MB 66.7MB/s 00:03
real 0m6.287s
user 0m0.993s
sys 0m0.541s
# time scp /tmp/testdata.txt localhost:/dev/null
Password:
testdata.txt 100% 200MB 66.7MB/s 00:03
real 0m4.839s
user 0m0.996s
sys 0m0.548s
► Delete the test file:
# rm /tmp/testdata.txt
You should see an improved througput.
13.9 The X Window System
For many years UNIX-like operating systems have been using the X Window System
(commonly just “X”). This system was designed to provide client/server,
hardware-independent and network-enabled graphical environment. The current version is
X11 which is widely used on UNIX and Linux platforms.
Confusion often arises among new X users regarding the concept of client and server,
because client and server are defined from an application point of view where other protocols
such as SSH, Telnet and FTP they are defined from an end user point of view. In X the server
runs on the hardware with the mouse, keyboard and monitor (usually a workstation or a
desktop), while the client runs on the UNIX or Linux server. Many Linux desktop users don’t
recognize this difference because they often run both the server and client on their desktop.
It is a common practice to connect from a PC (SSH client) to remote Linux (SSH server) and
then run an X application. It runs on remote Linux (X client) and displays on local PC (X
server).
The X communication protocol by its nature is not secure at all. For this reason it is often used
together with SSH protocol, which tunnels X11 traffic using encrypted (and thus secure)
communications.
X11 itself provides the ability to display graphics on raster display, nothing more. If the user
wants to be able to move, resize and otherwise manage windows, a window manager is
needed. There are many window managers available; some are lightweight while some are
more robust. So using a window manager is a good idea because it provides functionality
which one expects from a GUI.
216 The Virtualization Cookbook for RHEL 6