Remote control a Linux desktop using VNC

  Last modified on Monday 08 December 2014

Raspberry Pi is a less-than-$50 credit card sized computer that delivers all the power and flexibility of Linux, tools to start programming, and the opportunity to explore electronics courtesy of the onboard GPIO pins. There is an active community of Pi enthusiasts and plenty of resources to help you get started. I think this plucky little device has real potential as a home server!

One of the features I really like about the Pi is that the operating system runs off an SD card. Protecting the device's firmware from being mucked up makes it very easy to experiment with different Linux releases and configurations without any fear of bricking the device. I currently run Raspbian Linux - the default recommendation - on a SanDisk 32GB microSD with adapter but there is an active and growing list of alternatives.

The Pi has connectors for attaching an ethernet cable, USB peripherals such as keyboards and mice, and a monitor or TV permitting the device to serve as a complete standalone desktop computer. An alternative to dedicating input devices and a display to the Pi is to access the device via another computer using Virtual Networking Computing. VNC allows remote control of the Pi by transmitting all the display, keyboard, and mouse events to another computer.

To configure a VNC server and client:

0. Server

VNC enables a connection to a remote device display using two different methods: control an existing remote desktop attached to a physical display on a device running a VNC server (example: x11vnc); use a VNC server on the remote device to create a new desktop (example: tightvnc) for display on the VNC client device. This second option is what I configure to enable running the Pi as a headless device (no attached display or peripherals).

Temporary access to a display and USB input devices makes the inital configuration of the Pi and VNC an easier task. The alternative is connecting to the Pi using SSH.

Open or access a console on the Pi and install tightvncserver:

$ sudo apt-get update
$ sudo apt-get install tightvncserver

The first time the VNC server is launched it will prompt the user to create a password to permit access to the desktop:

$ vncserver
You will require a password to access your desktops.

Password:
Warning: password truncated to the length of 8.
Verify:
Would you like to enter a view-only password (y/n)? n
xauth:  file /home/USERNAME/.Xauthority does not exist

New 'X' desktop is HOSTNAME:1

Creating default startup script /home/USERNAME/.vnc/xstartup
Starting applications specified in /home/USRNAME/.vnc/xstartup
Log file is /home/USERNAME/.vnc/HOSTNAME:1.log

Default port on which vncserver runs is :1 which corresponds to the TCP port on which the server is running (5900+n = port number)... therefore the first instance is running on 5901. Running vncserver a second time will create a second instance running on the next free port, i.e :2 or 5902.

1. Client

Install a VNC client to connect with the newly-accessible remote Pi (example: xtightvncviewer is available for multiple platforms). On my Debian-powered laptop I install the ssvnc (Unix only) client:

$ sudo apt-get update
$ sudo apt-get install ssvnc

Start the client and connect to the Pi by supplying its ADDRESS:VNC_DESKTOP and the VNC desktop password:

SSVNC

... and use it with the ssh option since I already run openssh-server on the Pi and have it setup for ssh key authentication.

VNC

When finished with the session just close the VNC client window and use the -kill switch on the Pi to shut down the VNC server:

$ vncserver -kill :1

2. Optimize

On the Pi create myVNCserver with desired vncserver settings and place in ~/bin:

#!/bin/sh
vncserver -geometry 1800x1000 -depth 24 -dpi 96

Note that -geometry can be set to whatever is desired

With this setup VNC can be started and halted on demand. To have VNC auto-start at boot consult the Pi documentation for a sample /etc/init.d script. Since I plan to run my Pi as a headless server and rarely access the desktop I will just start VNC when I need it.

VNC does not use the Pi graphics processor and its memory allocation can be altered to assign more RAM to the CPU for running applications.

The desktop that vncserver puts up is controlled by ~/.vnc/xstartup. To load the lightweight Openbox window manager as an alternative to the default LXDE desktop environment, comment out the /etc/X11/Xsession line and replace with:

exec ck-launch-session openbox-session

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