x11vnc

$ x11vnc -loop -rfbauth ~/.vnc/passwd

-loop (restarting the x11vnc process whenever it terminates)

$ x11vnc -bg -reopen -forever -rfbauth ~/.vnc/passwd

-bg - is running on the background
-reopen - after you will log in and the x11vnc will be terminated this swich renew x11vnc connection
-forever - after you close vnc client the x11vnc server won't close but keep "running"

Authentication
create password file

-storepasswd pass file (default file is ~/.vnc/passwd)

use authentication on RFB protocol

-rfbauth passwd-file

References :
hykang's blog: x11vnc指令教學 
[xubuntu] X11vnc as boot loaded service

forward vnc to rdp(3389) using xrdp

// 安裝
# apt-get install tightvncserver
# apt-get install xrdp


// 啟動 vncserver
$ vncserver -geometry 1024x768  // it will set password




// 連結 RDP
$ rdesktop localhost

vnc server on CentOS

# yum install vnc-server

# useradd -m user1
# passwd user1

# su - user1
$ vncpasswd // it will create ~/.vnc/passwd

# vi /etc/sysconfig/vncservers

VNCSERVERS="1:user1 2:user2"
VNCSERVERARGS[1]="-geometry 800x600"
VNCSERVERARGS[2]="-geometry 640x480"

# /etc/init.d/vncserver start

$ vi ~/.vnc/xstartup
客製化啟動 x

# /etc/init.d/vncserver restart



Reference :
HowTos/VNC-Server - CentOS Wiki