Showing posts from February, 2014

Converting from linear to logarithmic scale

A simple function useful to plot a logarithmic scale. Just provide it with the min and max values of the scale and the value you want to convert - and you'll get in return a value as it should be positioned on a logarithmic scale in the given range.
public double toLogScale(double min, double max,double val) { double logmin = Math.log(min); double logmax = Math.log(max); double logscale = (Math.log(val)-logmin) / (logmax-logmin); return min+(max-min)*logscale; }

Ubuntu desktop in the cloud accessible with VNC

To create a Ubuntu desktop on Amazon EC2 that can be accessed by VNC I did the following steps:

1. Create 64-bit Ubuntu server instance
2. Install ubuntu desktop:

sudo apt-get install ubuntu-desktop

3. Install x11vnc

sudo apt-get install x11vnc

4. Install xvfb

sudo apt-get install xvfb

5. Configure x11vnc

sudo nano /etc/init/x11vnc.conf
start on login-session-start script /usr/bin/x11vnc -xkb -auth /var/run/lightdm/root/:0 -noxrecord -noxfixes -noxdamage -rfbauth /etc/x11vnc.pass -forever -bg -rfbport 5900 -o /var/log/x11vnc.log end script
And you should also set a password for your vnc sessions:

sudo x11vnc -storepasswd /etc/x11vnc.pass
6. Configure X server to use xvfb:

(Add the xserver-command line)

sudo nano /etc/lightdm/lightdm.conf
[SeatDefaults] greeter-session=unity-greeter user-session=ubuntu xserver-command=/etc/X11/xinit/xserverrc
(Replace the exec line)

sudo nano /etc/X11/xinit/xserverrc #!/bin/sh #exec /usr/bin/X -nolisten tcp "$@" exec Xv…