In this tutorial, we will learn to install the VNC server & secure VNC server sessions with TLS encryption.
This method has been tested on CentOS 6 & 7 but should work on other versions/OS as well (RHEL, Scientific Linux, etc).

(Recommended Read: Ultimate guide for Securing SSH sessions )

Installing VNC server

Before we install the VNC server on our machines, make sure we have a working GUI. If GUI is not installed on our machine, we can install it by executing the following command,

# yum groupinstall “GNOME Desktop”

Now we will tigervnc as our VNC server, to install it run,

# yum install tigervnc-server

Once VNC server has been installed, we will create a new user to access the server,

# useradd vncuser

& assign it a password for accessing VNC by using the following command,

# vncpasswd vncuser

Now we have a little change in configuration on CentOS 6 & 7, we will first address the CentOS 6 configuration,

CentOS 6

Now we need to edit VNC configuration file,

# vim /etc/sysconfig/vncservers

& add the following lines,

VNCSERVERARGS[1]="-geometry 1024x768"

Save the file & exit. Next, restart the VNC service to implement the changes,

# service vncserver restart

& enable it at boot,

# chkconfig vncserver on

CentOS 7

On CentOS 7, /etc/sysconfig/vncservers file has been changed to /lib/systemd/system/vncserver@.service. We will use this configuration file as the reference, so create a copy of the file,

# cp /lib/systemd/system/vncserver@.service /etc/systemd/system/vncserver@:1.service

Next, we will edit the file to include our created user,

# vim /etc/systemd/system/vncserver@:1.service

& edit the user on the following 2 lines,

ExecStart=/sbin/runuser -l vncuser -c "/usr/bin/vncserver %i"

Save file & exit. Next, restart the service & enable it at boot,

# systemctl restart vncserver@:1.service
# systemctl enable vncserver@:1.service

We now have our VNC server ready & can connect to it from a client machine using the IP address of VNC server. But we before we do that, we will secure our connections with TLS encryption.

Securing the VNC session

To secure VNC server session, we will first configure the encryption method to secure VNC server sessions. We will be using TLS encryption but can also use SSL encryption. Execute the following command to start using TLS encryption on the VNC server,

# vncserver -SecurityTypes=VeNCrypt,TLSVnc

You will be asked to enter a password to access VNC (if using any other user, then the above-mentioned user)

secure vnc server

We can now access the server using the VNC viewer from the client machine, use the following command to start VNC viewer with a secure connection,

# vncviewer -SecurityTypes=VeNCrypt,TLSVnc

here, is the IP address of the VNC server.

secure vnc server

Enter the password & we can then access the server remotely & that too with TLS encryption.

This completes our tutorial, feel free to send your suggestions or queries using the comment box below.

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