Linux system VNC Configuration

VNC Overview

VNC (Virtual network Computing) is an abbreviation for a computer that is virtualized. VNC is an excellent remote control tool software developed by the prestigious European Research Laboratory at T. VNC is a free, open source software based on UNIX and Linux operating systems that is powerful, efficient and practical, with performance comparable to any remote control software in Windows or MAC. In Linux, VNC consists of the following four commands: VNCSERVER,VNCVIEWER,VNCPASSWD, and Vncconnect. In most cases, only two of these commands are required: Vncserver and Vncviewer. At the moment, the original/T version is no longer in use, as more significant improvements have been made in the branching versions, such as RealVNC, VNC tight and UltraVNC. Real VNC is currently the most active and powerful mainstream application.

RealVNC Official website: http://www.realvnc.com/

Tight VNC official website: http://www.tightvnc.com/

ULTRAVNC official website: http://www.uvnc.com/

VNC principle

The VNC system consists of a client, a server, and a protocol. The purpose of VNC's server is to share the screen of the machine it is running on, and the server passively allows the client to control it. The VNC client (or Viewer) observes the control server and interacts with the server. The VNC protocol Protocol (RFB) is a simple protocol that transmits the original image of the server to the client (a square lattice of data on an X, y location) and the client transmits the event message to the server.

The server sends a small square frame cache to the client, in the simplest case, the VNC protocol uses a lot of bandwidth, so a variety of methods are invented to reduce the expense of communication, for example, there are various coding methods to determine the most efficient way to transmit these lattice blocks.

The protocol allows the client and the server to protocol which encoding is used, the simplest encoding, which is supported by most clients and the server, is the original encoding of the scanned data from left to right pixels, and when the original fullscreen is sent, only the changed block area is sent. This code works very well with only a small number of screen changes between when scrolling (like mouse keys moving on the desktop, or hitting text at the cursor), but if a lot of pixels change bandwidth at the same time it will increase very high, like dragging a window or watching a full-screen video.

VNC uses TCP ports 5900 through 5906 by default, while Java's VNC clients use 5800 to 5806. A server can connect a client with "listening mode" in 5500 ports, one of the benefits of using a listening mode is that the server does not need to set up a firewall.

VNC on Unix is called Xvnc and plays two roles, it is x server for the X Window System application, and it is a VNC server program for the VNC client.

1. Verify that VNC is installed
   By default, the Red Hat Enterprise Linux Installer installs the VNC service on the system.
   Verify that the VNC service is installed and view the installed VNC version
   [Email protected] ~]# rpm-q vnc-server
   Vnc-server-4.1.2-9.el5
   [Email protected] ~]#
   
   If the system is not installed, you can find the RPM installation package vnc-server-4.1.2-9.el5.x86_64.rpm of the VNC service under the server directory of the operating system installation disk, the installation command is as follows
   rpm-ivh/mnt/server/vnc-server-4.1.2-9.el5.x86_64.rpm
   
   2. Start the VNC service
   Use the Vncserver command to start the VNC service, the command format is "Vncserver: Desktop Number", where "desktop number" as a "number" means, each user needs to occupy 1 desktop
   Start a desktop with a number of 1 for example, below
   [Email protected] ~]# vncserver:1
   
   You'll require a password to access your desktops.
   
   Password:
   Verify:
   Xauth:creating new Authority file/root/. Xauthority
   
   New ' testdb:1 (root) ' Desktop is testdb:1
   
   Creating default startup script. /root/.vnc/xstartup
   Starting applications specified In/root/.vnc/xstartup
   Log file Is/root/.vnc/testdb:1.log
   
   During the execution of the above command, because it is the first time to execute, you need to enter a password, this password is encrypted in the user's home directory in the. VNC subdirectory (/ROOT/.VNC/PASSWD), and the user's home directory in the. VNC subdirectory automatically establishes the Xstartup profile ( /root/.vnc/xstartup), the configuration information from the file is read every time the VND service is started.
   There is also a "testdb:1.pid" file under the btw:/root/.vnc/directory that records the process number that corresponds to the acquired operating system after VNC is started, which is used to accurately locate the process number when the VNC service is stopped.
   
   The relationship between the port number used by the 3.VNC service and the desktop number
   The port number used by the VNC service is related to the desktop number, and VNC uses the TCP port starting with 5900, the corresponding relationship is as follows
   The desktop number is "1"----port number is 5901
   The desktop number is "2"----port number is 5902
   The desktop number is "3"----port number is 5903
   ......
   The Java-based VNC client Web service TCP port starts at 5800 and is related to the desktop number, which corresponds to the following
   The desktop number is "1"----port number is 5801
   The desktop number is "2"----port number is 5802
   The desktop number is "3"----port number is 5803
   ......
   Based on the above introduction, if Linux turned on the firewall function, you need to manually open the appropriate port to open the desktop number "1" the corresponding port as an example, the command is as follows
   [[email protected] ~]# iptables-i input-p TCP--dport 5901-j ACCEPT
   [[email protected] ~]# iptables-i input-p TCP--dport 5801-j ACCEPT
   
   4. Test VNC Service
   The first method is to use the VNC viewer software Landing test, the operation process is as follows
   Launch the VNC viewer software---server input "144.194.192.183:1"-click "OK"-Password enter the login password-click "OK" to log into the X-window graphical desktop environment--& Gt Test success
   The second method is to use a Web browser (such as Firefox,ie,safari) to log on to the test, the following procedures
   Address bar Input http://144.194.192.183:5801/--the VNC viewer for Java (this tool is a VNC client program written in Java) interface, while jumping out of the VNC Viewer dialog box, enter "144.194.192.183:1" click "OK"--Password Enter the login password-click "OK" Login to X-window graphical desktop environment-Test success
   (Note: VNC Viewer for Java requires JRE support, if the page cannot be displayed, indicating that no JRE is installed, you can download the latest JRE to http://java.sun.com/javase/downloads/index_jdk5.jsp here for installation)
   
   5. Configure the VNC graphical desktop environment for the KDE or GNOME desktop environment
   If you are configured according to my method above, landing on the desktop after the effect is very simple, only one shell to use, this is why? How can I see a cute and beautiful KDE or GNOME desktop environment? Answer as follows
   It's so ugly because the VNC service uses the TWM graphical desktop environment by default and can be modified in the VNC configuration file Xstartup, first look at this configuration file
   [Email protected] ~]# Vi/root/.vnc/xstartup
   #!/bin/sh
   
   # Uncomment the following-lines for normal desktop:
   # unset Session_manager
   # EXEC/ETC/X11/XINIT/XINITRC
   
   [-x/etc/vnc/xstartup] && Exec/etc/vnc/xstartup
   [-R $HOME/. Xresources] && Xrdb $HOME/. Xresources
   Xsetroot-solid Grey
   Vncconfig-iconic &
   Xterm-geometry 80x24+10+10-ls-title "$VNCDESKTOP Desktop" &
   TWM &
   
   Change the last line of this xstartup file to "Startkde &", and then restart the Vncserver service to log in to the KDE desktop environment
   Change the last line of this xstartup file to "Gnome-session &", and then restart the Vncserver service to log in to the GNOME desktop environment
   
   How to restart the Vncserver service:
   [Email protected] ~]# vncserver-kill:1
   [Email protected] ~]# vncserver:1
   
   6. Configure multiple Desktops
   You can use the following method to start VNC for multiple desktops
   Vncserver:1
   Vncserver:2
   Vncserver:3
   ......
   However, this method of manual startup will expire after the server restarts, so here's how to get the system to automatically manage VNC for multiple desktops by adding information that needs to be managed automatically to the/etc/sysconfig/vncservers configuration file. The following is the example of a desktop 1 root user Desktop 2 for an Oracle User:
   Format: vncservers= "desktop number: User name to use Desktop number: User name used"
   [Email protected] ~]# vi/etc/sysconfig/vncservers
   vncservers= "1:root 2:oracle"
   vncserverargs[1]= "-geometry 1024x768"
   vncserverargs[2]= "-geometry 1024x768"
   
   7. Modify the password for VNC access
   Using the command vncpasswd to modify the VNC password for different users, it is important to note that if VNC is configured with different users, it needs to be modified separately to the respective user, for example, in my experiment, the root user and Oracle user need to modify the process as follows:
   [Email protected] ~]# VNCPASSWD
   Password:
   Verify:
   [Email protected] ~]#
   
   8. Start and stop the VNC service
   1) Start the VNC service command
   [[email protected] ~]#/etc/init.d/vncserver start
   Starting VNC Server:1:root
   New ' testdb:1 (root) ' Desktop is testdb:1
   
   Starting applications specified In/root/.vnc/xstartup
   Log file Is/root/.vnc/testdb:1.log
   
   2:oracle
   New ' Testdb:2 (Oracle) ' Desktop is Testdb:2
   
   Starting applications specified In/home/oracle/.vnc/xstartup
   Log file Is/home/oracle/.vnc/testdb:2.log
   
   [OK]
   2) Stop the VNC service command
   [[email protected] ~]#/etc/init.d/vncserver stop
   Shutting down VNC server:1:root 2:oracle [OK]
   
   3) Restart the VNC service command
   [Email protected] ~]#/etc/init.d/vncserver restart
   Shutting down VNC server:1:root 2:oracle [OK]
   Starting VNC Server:1:root
   New ' testdb:1 (root) ' Desktop is testdb:1
   
   Starting applications specified In/root/.vnc/xstartup
   Log file Is/root/.vnc/testdb:1.log
   
   2:oracle
   New ' Testdb:2 (Oracle) ' Desktop is Testdb:2
   
   Starting applications specified In/home/oracle/.vnc/xstartup
   Log file Is/home/oracle/.vnc/testdb:2.log
   
   [OK]
   
   4) Set up VNC service to load automatically with system boot
   The first method: Use the "NTSYSV" command to start the graphical service configurator, add an asterisk before the Vncserver service, click OK, and the configuration is complete.
   The second method: use "Chkconfig" in the command-line mode of operation, command using the following (predict Chkconfig detailed use method please self-help man a bit)
   [Email protected] ~]# chkconfig vncserver on
   [Email protected] ~]# chkconfig--list vncserver
   Vncserver 0:off 1:off 2:on 3:on 4:on 5:on 6:off
   
   9. Summary
   The detailed configuration method of VNC has been finished, hoping to be helpful to everyone. VNC is very lightweight and convenient for remotely invoking a graphical interface, making use of it!
   
   
   

Linux system VNC Configuration