Changing the resolution of a VNC session in linux

Question

I use VNC to connect to a Linux workstation at work   At work I have a 20  monitor that runs at 1600x1200  while at home I use my laptop with its resolution of 1440x900  If I set the vncserver to run at 1440x900 I miss out on a lot of space on my monitor  whereas if I set it to run at 1600x1200 it doesn t fit on the laptop s screen  and I have to scroll it all the time   Is there any good way to resize a VNC session on the fly   My VNC server is RealVNC E4 x  I don t remember the exact version  running on SuSE64

User · Answer

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":

Start a VNC session with a geometry matching the physical display:
```
$ vncserver -geometry 1600x900 :1
```
On the "2560x1600" computer start the VNC viewer (I prefer Remmina) and connect to the remote VNC session:
```
host:5901
```
Once inside the VNC session start up a terminal window.

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.

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

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

In the above xrandr output look for the display name on the second line:
```
VNC-0 connected 1600x900+0+0 0mm x 0mm
```
Bind the new modeline to the current VNC virtual monitor:
```
$ xrandr --addmode VNC-0 "2560x1600_60.00"
```
Use it:
```
$ xrandr -s "2560x1600_60.00"
```

User · Answer

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

User · Answer

Solution by  omiday worked for me in Xvnc TigerVNC 1 1 0  so I condensed it into a single bash function vncsize x y  Use it like this  vncsize 1400 1000  It works for any VNC output name   quot default quot  or  quot VNC-0 quot   function vncsize       local x  1 y  2     local mode     if mode   cvt  quot  x quot   quot  y quot  2 gt  dev null      then         if     mode     quot Modeline       quot             then             local newMode   BASH REMATCH 1     quot                local modeName   newMode                  local newSize     modeName     quot x                    local screen   xrandr -q grep connected cut -d    -f1              xrandr --newmode  newMode             xrandr --addmode  quot  screen quot   quot  modeName quot              xrandr --size  quot   newSize 0  x  newSize 1   quot   amp  amp                  return 0         else             echo  quot Unable to parse modeline for   x  y  from  mode quot              return 2         fi     else         echo  quot    x  y  is not a valid X Y pair quot          return 1     fi

User · Answer

I m not sure about linux  but under windows  tightvnc will detect and adapt to resolution changes on the server    So you should be able to VNC into the workstation  do the equivalent of right-click on desktop  properties  set resolution to whatever  and have your client vnc window resize itself accordingly

User · Answer

Perhaps the most ignorant answer I ve posted but here goes  Use TigerVNC client viewer and check  Resize remote session to local window  under Screen tab of options   I don t know what the      TigerVNC client tells remote vncserver or xrandr or Xvnc or gnome or     but it resizes when I change the TigerVNC Client window   My setup    Tiger VNC Server running on CentOS 6  Hosting GNOME desktop   Works with RHEL 6 6 too  Windows some version with Tiger VNC Client    With this the resolution changes to fit the size of the client window no matter what it is  and it s not zooming  it s actual resolution change  I can see the new resolution in xrandr output    I tried all I could to add a new resolution to the xrandr  but to no avail  always end up with  xrandr  Failed to get size of gamma for output default  error   Versions with which it works for me right now  although I ve not had issues with ANY versions in the past  I just install the latest using yum install gnome-  tigervnc-server and works fine    OS  RHEL 6 6  Santiago  VNC Server  Name          tigervnc-server Arch          x86 64 Version       1 1 0 Release       16 el6    May be this is relevant     xrandr --version xrandr program version       1 4 0 Server reports RandR version 1 4       I start the server using vncserver -geometry 800x600   Xvnc is started by vncserver with following args   usr bin Xvnc  1 -desktop plabb13 sgdcelab sabre com 1  sg219898  -auth  login sg219898  Xauthority  -geometry 800x600 -rfbwait 30000 -rfbauth  login sg219898  vnc passwd -rfbport 5901 -fp catalogue  e tc X11 fontpath d -pn     I m running GNOME  installed using sudo yum install gnome-   Name          gnome-desktop Arch          x86 64 Version       2 28 2 Release       11 el6  Name          gnome-session Arch          x86 64 Version       2 28 0 Release       22 el6  Connect using Tiger 32-bit VNC Client v1 3 1 on Windows 7

User · Answer

Interestingly no one answered this  In TigerVNC  when you are logged into the session  Go to System  gt  Preference  gt  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

User · Answer

I have a simple idea  something like this      bin sh  echo  xrandr --current   grep current   awk   print  8     gt  gt  RES1 echo  xrandr --current   grep current   awk   print  10     gt  gt  RES2 cat RES2   sed -i  s    g  RES2  P1RES   cat RES1  P2RES   cat RES2  rm RES1 RES2 echo   P1RES  x   P2RES   gt  gt  RES RES   cat RES     Play The Game    Finish The Game with Lower Resolution  xrandr -s  RES   Well  I need a better solution for all display devices under Linux and Similars S O

User · Answer

As far as I know there s no way to change the client s resolution just using VNC  as it is just a  monitor mirroring  application   TightVNC however  which is a VNC client and server application  can resize the screen on the client side  i e  making everything a little smaller  similar to image resizing techniques in graphics programs   That should work if you don t use too small font sizes  VNC should theoretically be compatible between different VNC applications

User · Answer

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

User · Answer

Adding to Nathan s  accepted  answer   I wanted to cycle through the list of resolutions but didnt see anything for it   function vncNextRes        xrandr -s      xrandr   grep      sed  s       0-9         1    1    gt   dev null 2 gt  amp 1         xrandr -s 0     It gets the current index  steps to the next one and cycles back to 0 on error  i e  end     EDIT  Modified to match a later version of xrandr      is on end of line and no leading resolution identifier    function vncNextRes        xrandr -s      xrandr 2 gt  dev null   grep -n          sed  s        -2            xrandr -s 0

User · Answer

I think that depends on your window manager   I m a windows user  so this might be a wrong guess  but  Isn t there something called X-Server running on linux machines - at least on ones that might be interesting targets for VNC - that you can connect to with  X-Clients    VNC just takes everything that s on the screen and  tunnels it through your network   If I m not totally wrong then the  X  protocol should give you the chance to use your client s desktop resolution    Give X-Server on Wikipedia a try  that might give you a rough overview

User · Answer

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

User · Answer

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 gt  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 gt  xrandr -s 5   I m using TightVnc viewer as the client and it automatically adapts to the new resolution

User · Answer

On the other hand  if there s a way to   move an existing window from one   X-server to another  that might solve   the problem    I think you can use xmove to move windows between two separate x-servers  So if it works  this should at least give you a way to do what you want albeit not as easily as changing the resolution

User · Answer

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

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

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