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Archive for January, 2005
VNC over SSH, Part2: a quick HowTo on PuTTY
VNC over SSH, Part2: a quick HowTo on PuTTY
For those who like to use GUI based SSH client on Windows, here is a quick HowTo on establishing a SSH tunel for VNC using PuTTY. If you prefer command line, you can also try ssh under Cygwin.
This quick note is intended to supplement what I found on the Internet, which is http://pigtail.net/LRP/vnc It has good information that also covers NAT/firewall configuration you may need to do for establishing a SSH tunnel. For further information on PuTTY, pleasee the offical documentation at http://www.chiark.greenend.org.uk/~sgtatham/putty/docs.html
Disclaimer: These instructions are provided AS-IS. Try them at your own risk. For support, try online forums, which will be much faster than what I can do.
Before you get started, please make sure you have the latest version of PuTTY. At the time of writing, the current version is 0.56. You can get the latest binary form http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
Once you downloaded the binary, you can just execute the exe file and you see the image below (Figure 1). Replace the SSH_SERVER_HOST with the appropriate target host name or IP address of the machine running SSH server. If you do not have a SSH server running, see my original VNC over SSH piece.
Figure1
In my previous piece, I didn’t cover proxy configuration on SSH client. In PuTTY, there is an easy to use GUI that allows you to define yoru proxy server information. Please see Figure 2 below. Specify your proxy configuration in this section if you have one.
Figure 2
The next step is to specify tunnel configuration. The changes I done here are described below and shown in Figure 3:
- Check “Enable X11 forwarding”
- Enter “localhost:0″ for “X display location”
- Enter “5900″ for “Source port” (Note: Make sure you don’t already have a VNC server running at this port. Specify a different port if you already have a VNC server running at this port.)
- Enter “localhost:5900″ for “Destination”
- Click “Add” button. You should see “L5900 localhost:5900″ listed as shown below.
If you want to access another VNC Server in a private net through the gateway/firewall running SSH server, you can change the “Destination” to the host name/IP of that VNC Server. i.e. my_vnc_server:5900)
Figure 3
Before you establish a SSH tunnel, make sure you go back to the “Session” panel and save your configuration. (See Figure 1) I specified “myconnection” and “myconnection2″ as session names.
Once you saved your configuration, you can click on “Open” button. A terminal window will pop up asking for your user name and password. Enter the user name and password for the SSH server. After you successfully login, run your favorite VNC viewer, specify localhost:5900 (or whatever you specified in “Soruce port” in PuTTY. You should get a pop up asking for your VNC password.
VNC over SSH, a quick HowTo
VNC over SSH, a quick HowTo
I know this area is well documented. However, I still have to search through forums to find the missing information. So, to show my appreciation, I wanted to put this quick notes together. This is very rough. Feedbacks are welcome.
Disclaimer: This instruction is provided AS-IS. Try them at your own risk. For support, try online forums, which will be much faster than what I can do.
What it is?
For VNC, please see http://www.realvnc.com/
For SSH, please see http://www.openssh.com/
Where do I get the software?
For VNC, you can get it from http://www.realvnc.com. If you use Linux, you may already have it. Just do a which command to verify.
For SSH, I assume it is already installed. It is available out-of-box for Solaris 9 or better and Red Hat Linux. For windows client, use PUTTY http://www.chiark.greenend.org.uk/~sgtatham/putty/
How do I install VNC?
For VNC, If you download the software from realvnc.com, you can either follow the installation instruction by running the installation script. What I did for Solaris distribution was keeping all files in a user home directory to avoid using the root account. Make sure you update your PATH environment variable so that the user you want to use to run VNC server have access to it.
How do I configure the VNC Server?
For VNC on RedHat Enterprise Linux 4 beta 2, this is what I did:
-
su to root
-
Un-comment the following lines in /etc/sysconfig/vncservers
VNCSERVERS=”1:myusername”
VNCSERVERARGS[1]=”-geometry 800×600″ -
su to user you will use for connecting to VNC server
-
Run the vncpasswd command to set the password.
-
Restart VNC Server. Ex: /etc/init.d/sshd restart
For VNC on Solaris, here is what I did:
-
In order for VNC to work correctly with SSH, change AllowTcpForwarding parameter to yes in /etc/ssh/sshd_config. Ex: AllowTcpForwarding yes
-
To start VNC server:
-
su to the user that has access to VNC software (if you installed in a user home directory) or use a user of your choice.
-
Run vncserver -geometry 800×600
-
How do I establish a SSH tunnel?
Below is the command format that I used to establish a SSH tonnel between my client machien and the SSH server machine. Replace SSH_SERVER with the appropriate host name or IP. Replace USER_NAME with the appropriate user name.
/bin/ssh SSH_SERVER -l USER_NAME -L 5901:localhost:5901 -N -f
The above command will drop to background (due to -f option) and you should have your prompt back. Sometimes you may need to change localhost with an IP address, i.e. 127.0.0.1 If you setup your VNC server other than 5901, adjust this command accordingly. To find out which port your VNC server is open at, see VNC server log in .ssh directory in your user home directory on the server side.
How do I verify that the SSH tunnel is valid?
One way to verify the tunnel is to telnet localhost 5901. You should see a RFB… line.
What if I am behind a proxy server?
Check with your network administrator for socks proxy server information. SSH comand can be configured to use a socks proxy server. The one that I used is specific to my environment and therefore it is useless for public sharing at this time. At least I can say that I used -o option to add proxy information.
How to I use VNC over a SSH tunnel?
Just point your VNC client (vncviewer) to localhost:1 or localhost:5901. Then you should be asked to enter a password. If you get an error, check if the tunnel is valid (see above). You can also double check the port number that the VNC server listens.
What if I want to connect to a VNC server that is within a private net protected by a gateway running SSHD?
SSH can also do forwarding, try the following command:
/bin/ssh SSH_SERVER -l USER_NAME -L 5901:MY_VNC_SERVER_HOST:5901 -N -f
Change localhost in the -L option to the IP/host name of your VNC server.
Comments or Suggestions? Please feel free to leave me one!
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Introduction to Data Communications
http://www.techbooksforfree.com/intro_to_data_com/toc.html
Mount option in Linux
The most universal file system format is fat32 (vfat). By default, a Linux system may mount the partition as root that will prevent regular user from writing to the partition. To work around that, add “user” option in the mount entry in the /etc/fstab file.
A Telnet Trick
To get out of a telnet session, press Control + close bracket, then enter “quit” to quit the telnet session.
Oracle links
http://www.fors.com/orasupp/rdbms/misc/423_1.HTM
http://www.dbazine.com/oracle.shtml
