Changing the resolution of a VNC session in linux [closed]

Question

Real VNC server 4.4 includes support for Xrandr, which allows resizing the VNC. Start the server with:

vncserver -geometry 1600x1200 -randr 1600x1200,1440x900,1024x768

Then resize with:

xrandr -s 1600x1200
xrandr -s 1440x900
xrandr -s 1024x768

Found out that the vnc4server (4.1.1) shipped with Ubuntu (10.04) is patched to also support changing the resolution on the fly via xrandr. Unfortunately the feature was hard to find because it is undocumented. So here it is...

Start the server with multiple 'geometry' instances, like:

vnc4server -geometry 1280x1024 -geometry 800x600

From a terminal in a vncviewer (with: 'allow dymanic desktop resizing' enabled) use xrandr to view the available modes:

xrandr

to change the resulution, for example use:

xrandr -s 800x600

Thats it.

I'm running TigerVNC on my Linux server, which has basic randr support. I just start vncserver without any -randr or multiple -geometry options.

When I run xrandr in a terminal, it displays all the available screen resolutions:

bash> xrandr
 SZ:    Pixels          Physical       Refresh
 0   1920 x 1200   ( 271mm x 203mm )   60
 1   1920 x 1080   ( 271mm x 203mm )   60
 2   1600 x 1200   ( 271mm x 203mm )   60
 3   1680 x 1050   ( 271mm x 203mm )   60
 4   1400 x 1050   ( 271mm x 203mm )   60
 5   1360 x 768    ( 271mm x 203mm )   60
 6   1280 x 1024   ( 271mm x 203mm )   60
 7   1280 x 960    ( 271mm x 203mm )   60
 8   1280 x 800    ( 271mm x 203mm )   60
 9   1280 x 720    ( 271mm x 203mm )   60
*10  1024 x 768    ( 271mm x 203mm )  *60
 11   800 x 600    ( 271mm x 203mm )   60
 12   640 x 480    ( 271mm x 203mm )   60
Current rotation - normal
Current reflection - none
Rotations possible - normal
Reflections possible - none

I can then easily switch to another resolution (f.e. switch to 1360x768):

bash> xrandr -s 5

I'm using TightVnc viewer as the client and it automatically adapts to the new resolution.

I think your best best is to run the VNC server with a different geometry on a different port. I would try based on the man page

$vncserver :0 -geometry 1600x1200
$vncserver :1 -geometry 1440x900

Then you can connect from work to one port and from home to another.

Edit: Then use xmove to move windows between the two x-servers.

As this question comes up first on Google I thought I'd share a solution using TigerVNC which is the default these days.

xrandr allows selecting the display modes (a.k.a resolutions) however due to modelines being hard coded any additional modeline such as "2560x1600" or "1600x900" would need to be added into the code. I think the developers who wrote the code are much smarter and the hard coded list is just a sample of values. It leads to the conclusion that there must be a way to add custom modelines and man xrandr confirms it.

With that background if the goal is to share a VNC session between two computers with the above resolutions and assuming that the VNC server is the computer with the resolution of "1600x900":

1. Start a VNC session with a geometry matching the physical display:

   $ vncserver -geometry 1600x900 :1
   

2. On the "2560x1600" computer start the VNC viewer (I prefer Remmina) and connect to the remote VNC session:

   host:5901
   

3. Once inside the VNC session start up a terminal window.

4. Confirm that the new geometry is available in the VNC session:

   $ xrandr
   Screen 0: minimum 32 x 32, current 1600 x 900, maximum 32768 x 32768
   VNC-0 connected 1600x900+0+0 0mm x 0mm
      1600x900      60.00 +
      1920x1200     60.00  
      1920x1080     60.00  
      1600x1200     60.00  
      1680x1050     60.00  
      1400x1050     60.00  
      1360x768      60.00  
      1280x1024     60.00  
      1280x960      60.00  
      1280x800      60.00  
      1280x720      60.00  
      1024x768      60.00  
      800x600       60.00  
      640x480       60.00  
   

   and you'll notice the screen being quite small.

5. List the modeline (see xrandr article in ArchLinux wiki) for the "2560x1600" resolution:

   $ cvt 2560 1600
   # 2560x1600 59.99 Hz (CVT 4.10MA) hsync: 99.46 kHz; pclk: 348.50 MHz
   Modeline "2560x1600_60.00"  348.50  2560 2760 3032 3504  1600 1603 1609 1658 -hsync +vsync
   

   or if the monitor is old get the GTF timings:

   $ gtf 2560 1600 60
   # 2560x1600 @ 60.00 Hz (GTF) hsync: 99.36 kHz; pclk: 348.16 MHz
   Modeline "2560x1600_60.00"  348.16  2560 2752 3032 3504  1600 1601 1604 1656 -HSync +Vsync
   

6. Add the new modeline to the current VNC session:

   $ xrandr --newmode "2560x1600_60.00"  348.16  2560 2752 3032 3504  1600 1601 1604 1656 -HSync +Vsync
   

7. In the above xrandr output look for the display name on the second line:

   VNC-0 connected 1600x900+0+0 0mm x 0mm
   

8. Bind the new modeline to the current VNC virtual monitor:

   $ xrandr --addmode VNC-0 "2560x1600_60.00"
   

9. Use it:

   $ xrandr -s "2560x1600_60.00"
   

Interestingly no one answered this. In TigerVNC, when you are logged into the session. Go to System > Preference > Display from the top menu bar ( I was using Cent OS as my remote Server). Click on the resolution drop down, there are various settings available including 1080p. Select the one that you like. It will change on the fly.

Make sure you Apply the new setting when a dialog is prompted. Otherwise it will revert back to the previous setting just like in Windows

Guys this is really simple.

login via ssh into your pi

execute

vncserver -geometry 1200x1600

This will generate a new session :1

connect with your vnc client at ipaddress:1

Thats it.