Monday, December 31, 2012

How to use VNC to view a remote system

VNC is a free 3rd party program that allows a remote login, similar to Remote Desktop in Windows or Daemonware. One nice thing about VNC, is that it's multi-platform. It works on Windows, UNIX, BSD, Linux and MAC. The down side to using VNC is that it's insecure, but you can wrap it in a SSH tunnel. Most of my experience with VNC is on Solaris and Red Hat. Most of the examples below are from a Solaris server.

To see if any VNC sessions is running on your server run the command below. # ps -ef|grep vnc
If you have a session running it will look like this. rich 15137 14170  0 Nov 24 ?    0:00  vncconfig -iconic
rich  538  8833   0 Nov 24 ?    7:34  Xvnc :1 -desktop server:1 (rich) -auth /home/rich/.Xauthority -geometry 1900

To start a basic VNC server session just type vncserver. # vncserver After you run this command you will get a session ID number. For example the first user of VNC server will get session number 1. When you connect to the session from a remote computer you use the hostname:1.

You will also need to set the VNC password to connect the session. # vncpasswd This sets the password for your account.

If you want more options, check the these popular options below. For screen size use -geometry widthxhight. If the computer you are connecting from doesn't have VNC Viewer installed then, you can use the -httpd option to connect using a web browser.  # vncserver :3 -geometry 800x600 -http

VNC is installed on MACs and you can turn on the VNC server by going to System Preferences -->  Sharing. Select Remote Management and then click Computer settings. In the drop down select VNC viewers may control screen with password. Then put in desired password in box.

The xstartup file controls the desktop you get. Uncomment lines 4 & 5 to get a gnome desktop.

Sometimes you need to shutdown the VNC session your using. # vncserver -kill :#Replace # with the session number VNC gave you.

Now that you have started the VNC server you will want to connect to use it. From a UNIX or Linux  you run the following command. vncviewer hostname:1 # vncviewer server1:1
If you are using VNC from a Windows PC, then there is a VNC viewer application.

Warning: If you auto-mount your home directory. Beware that different operating systems have different setting in the xstartup file. All VNC sessions use the same xstartup file, so changes made by you or the VNC program will effect the VNC experience. I ran into an issue when I tried to use the gnome desktop on both a RHEL & Solaris 10 servers. When I got the gnome desktop working for RHEL the gnome desktop was unusable with Solaris 10. The best way to get around this is to use different accounts or different windowing programs on different operating systems.

Important VNC files
$HOME/.vnc/xstartup -- The file that controls them all. This is the main config file used for the session on VNC server.

$HOME/.vnc/passwd -- The VNC password file

$HOME/.vnc/host:display#.log -- The log file for Xvnc and applications started in xstartup

$HOME/.vnc/ -- Identifies the Xvnc process ID, used by the -kill option.

Package list for Solaris 10
SUNWxvnc                VNC Server
SUNWvncviewer       VNC Viewer