Connect to a linux box to see the remote screen using VNC through ssh tunnel

remotevnc.sh

#!/usr/bin/env bash
#
# Script to connect to remote machine via ssh and export X11 via vnc using a ssh tunnel
#
# Author: Jose Riguera <jriguera@gmail.com> December 2009
# License: GNU General Public License v2 or later
#
# x11vnc must be installed on remote host
# xvnc4viewer must be installed on local host
#
### Config options

SSHOPTIONS="-oConnectTimeout=3 -f"
VNCDISPLAY=":0"
VNCBASEPORT=5900
VNCCOMMAND="x11vnc -safer -localhost -nopw -once -bg"
VNCVIEWER="xvnc4viewer -Shared -LowColourLevel 2"

###

PROGRAM=$(basename "$0")
PROGRAM_DIR=$(cd $(dirname "$0"); pwd)
PROGRAM_FULLPATH="$PROGRAM_DIR/$PROGRAM"
PROGRAM_CONF="${PROGRAM_DIR}/${PROGRAM%%.*}.conf"
PROGRAM_LOG="/tmp/${PROGRAM%%.*}-$(date +%F-%H-%M).log"
LOG="/dev/null"

###

# Avoid be interrupted by child or keyboard
trap "echo" SIGINT SIGSEGV SIGQUIT
set +e

# All variables have to be defined!
# set -o nounset

# Print a message and exit with error
die() {
    logger -i -t "$PROGRAM" -p local0.notice -- "ERROR: $@"
    echo "$PROGRAM ERROR: $@"
    exit 1
}

# Logs a message with error
logg() {
    logger -i -p local0.notice -t "$PROGRAM" -- "$@" 
    echo "$PROGRAM: $@" >>${LOG}
}

# Logs and Print a message with error
perror() {
    logg $@
    echo "$PROGRAM: $@"
}


help() {
    cat <<EOF
Usage:
    $PROGRAM [-c <file>] [-l [<file>]] [-n] user@machine [display]

Launch a VNC command via ssh on remote machine.

    -c <file>   Config file. Default config file is ${PROGRAM_CONF}
    -l [<file>] Log file that stores stdout messages. Default log is ${PROGRAM_LOG}
    -n          Don't launch xvncviewer. The conexion will be waiting 120 seconds. 
    [display]	X11 display on remote machine in order to connect a VNC session. 
		Default value is ":0" and will be tunneled trough 5900 port on local
		machine. A value of ":1" will be mapped to 5901 port and so on, like
		the VNC protocol defines.
EOF
}


do_sshcmd() {
    local cmd="$1"
    local host="$2"
    local sshoptions="$3"

    local cmd_status=0
    local cmd_ssh="ssh $sshoptions $host $cmd"

    #echo "$cmd_ssh"
    logg "[ $(date +%F-%H-%M) ] -> [($host):$cmd_ssh]"
	$cmd_ssh 1>>${LOG} 2>>${LOG} 
    cmd_status=$?
    logg "[ $(date +%F-%H-%M) ] -> [($host):$cmd_ssh]: exit=$cmd_status" 
    return $cmd_status
}


do_process() {
    local machine="$1"
    local vncdisplay="$2"
    local launchvnc=$3

    local status=0
    local vncdesktop="localhost:0"
    local port=0
    local vnccommand="$VNCCOMMAND -display $vncdisplay"

    echo "Launching VNC on remote machine ..."
    do_sshcmd "$vnccommand" "$machine" "$SSHOPTIONS"
    sleep 5
    vncdesktop=$(cat ${LOG} | grep "The VNC desktop is:" | cut -d":" -f 3 )
    vncport=$(echo "$VNCBASEPORT + $vncdesktop" | bc)
    echo "The VNC desktop is: localhost:$vncdesktop" 
    echo "Setting ssh tunel on port $vncport ..."
    do_sshcmd "sleep 120" "$machine" "$SSHOPTIONS -L $vncport:localhost:$vncport"
    if [ $launchvnc = 1 ]; then
        echo "Launching vncviewer localhost:$vncdesktop ... "
        echo "Press F8 for options ..."
        $VNCVIEWER localhost:$vncdesktop >> ${LOG} 2>&1
    else
        echo "Waiting 120 seconds for connections on port $vncport (localhost:$vncdesktop) ..."
        sleep 120
    fi
    status=$?
    echo "Closing connections ..."
    wait
    return $status
}


########


#  Main Program
MACHINE=NONE
COMPONENT=none
DO=0
LOG2FILE=1
LAUNCHVNC=1
while [ $# -gt 0 ]; do
    case "$1" in
    -c) [ ! -z "$2" ] || die "The $1 switch requires the name of a config file!"
        arg_confile="$2"
        shift
    ;;
    -l) if [ ! -z "$2" ]; then
            if echo "$2" | grep -q "\." ; then
                arg_log="$2"
                shift
            fi
        fi
        LOG2FILE=1
    ;;
    -n) LAUNCHVNC=0
    ;;
    -h) help; exit 0
    ;;
    --) shift; break
    ;;
    -*) echo "$PROGRAM: Unknown argument $1"
        help; exit 0
    ;;
    *@*)
        MACHINE="$1"
        if [ ! -z "$2" ]; then
            COMPONENT="$2"
            shift
        fi
        DO=1
    ;;
    esac
    shift
done
# [ $DO = 0 ] && help && exit 0

# Configuration file
PROGRAM_CONF=${arg_confile:-$PROGRAM_CONF}
[ -f "$PROGRAM_CONF" ] && . "$PROGRAM_CONF"

# Logs
if [ $LOG2FILE = 1 ]; then
    PROGRAM_LOG=${arg_log:-$PROGRAM_LOG}
    echo "--- $PROGRAM_FULLPATH $PROGRAM_OPTS (at $(date))" >> $PROGRAM_LOG
    LOG=$PROGRAM_LOG
fi

# Settings
[ "X$COMPONENT" != "Xnone" ] && VNCDISPLAY="$COMPONENT"

# Main function
do_process "$MACHINE" "$VNCDISPLAY" $LAUNCHVNC
rvalue=$?

exit $rvalue

#EOF