Digital Internals

How to Disconnect a Remote Desktop Session

2010-07-27T08:59:55Z

Have you ever come across the error message “The terminal server has exceeded the maximum number of allowed connections” while trying to login to a Windows machine as an administrator?

The error message is displayed as Windows only allows two remote terminal services sessions for an administrator. Sometimes the error message is displayed even though there is only a single active session. The other session could be an hanging session that could have been disconnected in an abrupt manner.

If the Windows server is part of domain, just open the Terminal Services Manager to remove the invalid sessions. If the server is not part of a domain, you will need to connect to the machine locally or via telnet or ssh. Once logged in, run the following command to list the sessions:

c:\> query session
 SESSIONNAME       USERNAME                 ID  STATE   TYPE        DEVICE
>console                                     0  Conn    wdcon
 rdp-tcp                                 65536  Listen  rdpwd
                   Administrator             2  Disc    rdpwd
 rdp-tcp#3         administrator             3  Active  rdpwd

Do you notice that the session with an ID number of 2 is disconnected ?

We can now proceed to remove that session.

c:\> reset session 2

The offending session should now be closed. You can run the query command again to confirm that the session has been closed.

Disable Javascript No Right Click Restriction

2010-04-27T14:15:26Z

There are a number of sites that disable the right-mouse clicks to with the intention to prevent the theft of their web page content. A no right click restriction is implemented by manipulating the event objects in JavaScript.

All the scripts that I have seen, disable access to the browser context menu that is activated by a right-click. The main objective is to prevent the users from selecting the ‘View Page Source’ option in the context menu. But many people do not realise that the page source can be viewed by other means.

In Firefox, the keyboard shortcut, Ctrl-U, will open the page source window. Alternatively, there is also a ‘Page Source’ option under the ‘View’ menu in Firefox.

One way to disable the no right click restriction is to totally disable JavaScript. But this may interfere with the navigation of the site.

Another way is to run the following JavaScript code from the browser’s address bar and hit enter.

javascript:void(document.onmousedown=null);void(document.onclick=null);void(document.oncontextmenu=null)

Screensaver That Mimics The Blue Screen of Death

2010-03-29T10:40:57Z

Are you bored with your typical screen saver? If yes, read on…

The most feared color in the Windows world is blue! The Blue Screen of Death (BSOD) will pop up usually after encountering a critical system error in the Windows NT line of operating systems.

There is a BlueScreen screensaver from Sysinternals that not only authentically mimics a BSOD, but will simulate startup screens seen during a system boot.

Bluescreen’s BSOD and system start screen is obtained from your system configuration. I have been using it for a very long time and it has managed to fool even advanced Windows system administrators.

Download your Bluescreen screensaver here, and start scaring your friends and colleagues! Installation instructions can be found on the download page.

How to Confirm That Someone Has Blocked You on Facebook

2010-04-03T04:25:30Z

If you are not aware yet, every Facebook account has a privacy option to block users based on their name or e-mail address. Once you block someone, you cut all ties with them, including friendship, comments, etc. They will not be able to interact with you nor be able to search for you on Facebook.

Before trying to confirm if someone has blocked you on Facebook, let’s see how to block someone in Facebook.

Blocking Someone on Facebook

Logon to Facebook and goto ‘Block List’ under ‘Privacy Settings’
Search for the user to block based on the name or e-mail address< and click on the 'Block' link for the person you want to block

Confirm If Someone Has Blocked You on Facebook

Create another Facebook account using a new e-mail address
Search for the user you believe has blocked you using his/her name or e-mail address
If that person’s Facebook profile appears in the search result, they have most probably added you to their block list

If your search result does not return any result,the account could have been deactivated or the associated e-mail address could have been changed.

How to Redirect Output of Command Line Tools to Windows Clipboard

2010-01-17T12:53:08Z

I have recently discovered a new Windows command line tool, called 'clip' that can be used to redirect the output of CLI tools to the Windows Clipboard.

This command is available in Windows Vista but not found in Windows XP. It’s found in the %systemroot%\system32 directory.

To copy the output of a CLI tool to the Windows Clipboard, append ‘| clip’ to the end of the command. To retrieve the output, open Notepad or a text editor and click on ‘Paste’.

Clip can also be used with input redirection operator – ‘<’. To perform the redirection, prepend clip < to the command.

Below are some examples on how the program can be called.

C:\temp> type readmet.txt | clip

C:\temp> clip < readme.txt

I am not sure if such a tool is available in UNIX or Linux. But this feature can be easily emulated by redirecting the output to a file and opening the file in VI or a text editor.

How to Prevent Ubuntu from Setting BIOS Clock to UTC

2009-11-22T15:06:15Z

I have a dual-boot computer that boots Ubuntu and Windows 7. Whenever I boot into Ubuntu, the BIOS clock is automatically set to UTC time, even though my current timezone is UTC+8.

Microsoft Windows on other hand, assumes that the BIOS clock contains the local time. I am not sure if there’s a way to make Windows assume that the BIOS time is set to UTC, but I have found a way to stop Ubuntu from setting the BIOS clock to UTC.

Ubuntu has a variable settings file called rcS in the /etc/default directory. This file contains variables that affect the behaviour of startup scripts. One of the variables is the ‘UTC’ paramater. This parameter is used to govern how the BIOS or hardware clock is intepreted. If it’s set to ‘no’ then the system clock is assumed to be set to local time. If it’s set to ‘yes’ then it’s assumed to be set to UTC time.

To let Ubuntu interpret the system clock as local time, the ‘UTC’ parameter has to be set to ‘no’. To update the parameter in the file, run the following command in a terminal.

ibrahim@anfield:~$ sudo bash
[sudo] password for ibrahim:
root@trafford:~# sed 's/UTC=yes/UTC=no/' /etc/default/rcS > /tmp/rcS
root@trafford:~# mv -f /tmp/rcS /etc/default/rcS

To update the BIOS time to localtime, run hwclock as follows:

root@trafford:~# hwclock --systohc --localtime

How to Initiate Google Talk Group Chat in Pidgin

2009-10-31T14:08:50Z

Google has launched a new Group Chat feature in Google Talk. Even though Google Talk uses the open XML based XMPP protocol for it’s IM service, Pidgin, the open source multi-platform instant messaging client, has yet to support this useful feature.

I have absolutely no clue as to why this feature is not included in Pidgin. I have some of my colleagues on Google Talk and group chat is sometimes a necessary tool to get quick updates from colleagues working from different locations.

As Google Talk is based on a XML protocol, I decided to find out how a group chat is being initiated using Wireshark, a free packet sniffer cum analyzer.

Below is a snippet of a group chat request being sent from the official Google Talk client. Note the string: private-chat-11d12d21-46e5-4359-b0cd-44bc01bb82af@groupchat.google.com

The numbers in the string private-chat-11d12d21-46e5-4359-b0cd-44bc01bb82af@groupchat.google.com looks like a UUID number to me. We now have the necessary info to initiate a Google Talk group chat in Pidgin. Click on ‘Join a chat’ from the Buddies menu in Pidgin. You will get a pop-up window similar to the one below.

Enter the following fields:

Room – private-chat-11d12d21-46e5-4359-b0cd-44bc01bb82af
Server – groupchat.google.com

and click the Join button. You should now have a group chat window opened in Pidgin. You can now start inviting your contacts for a Google Talk group chat on Pidgin.

UNIX Shell Script to Calculate Tomorrow’s Date

2009-10-11T12:09:20Z

A couple of readers, upon reading this article to calculate yesterday’s date in a shell script, have requested for a similar script that can be used to calculate tomorrow’s date.

Even though such a script is quite straight forward to write, many people seem to be have problem with the leap year calculations. Anway, I have managed to come up with a script to help everyone. Read on.

If you are running Linux, it’s highly likely that you have a GNU version of the date command installed. With GNU date, you can get tomorrow’s date quite easily (without the help of any shell script) by running it as follows:

[ibrahim@anfield ~]$ date  -d "+1 day"
Thu Oct  8 06:26:25 PDT 2009

If you are running a commercial UNIX distribution instead of Linux, chances are that the date command will not support the ‘-d’ option. The script below can be used on such platforms to calculate tomorrow’s date instead. Save the following script to a file called tomorrow, chmod to 755 and copy it to a directory in your PATH.

#!/bin/sh

#
# Script to calculate tomorrow's date with custom output date format
#
# Author: ibrahim - www.digitalinternals.com
#

  # default output format
  defaultof="%Y%m%d"

  # check for input format, else use default format,
  # refer to 'man date' for help on format
  of=$defaultof
  [ $# -eq 1 ] && of="$1"

  # get today's date
  y=`date '+%Y'`
  m=`date '+%m'`
  d=`date '+%d'`

  #check for max number of days in current month
  days=31
  if [ $m -eq 4 ] || [ $m -eq 6 ] || [ $m -eq 9 ] || [ $m -eq 11 ] ; then
    days=30
  fi
  # check for leap year if feb
  if [ $m -eq 2 ]; then
    days=28
    leap1=`expr $y % 4`
    leap2=`expr $y % 100`
    leap3=`expr $y % 400`
    if [ $leap1 -eq 0 ] ; then
      if [ $leap2 -gt 0 ] || [ $leap3 -eq 0 ] ; then
        days=29
      fi
    fi
  fi

  # increment date
  if [ $d -eq $days ]; then
    d=1
    m=`expr $m + 1`
    if [ $m -eq 13 ]; then
      m=1
      y=`expr $y + 1`
    fi
  else
    d=`expr $d + 1`
  fi

  date -d "$y-$m-$d" +"$of"

Below are some examples on how the script can be called.

[ibrahim@anfield ~]$ date
Wed Oct  7 06:36:45 PDT 2009

[ibrahim@anfield ~]$ tomorrow
20091008

[ibrahim@anfield ~]$ tomorrow "%c"
Thu 08 Oct 2009 12:00:00 AM PDT

[ibrahim@anfield ~]$ tomorrow "%Y-%m-%d"
2009-10-08

How to Use Google Currency Converter

2009-09-13T07:16:28Z

Are you going on a holiday and need to find out exchange rate of your holiday destination? You will no longer need to search for a site that does currency conversions. Google is able to perform the currency conversion using a simple search query.

All you need to do is to perform a Google search using a special syntax, similar to: 100 SGD in USD.

Google will interpret the query as what is 100 Singapore Dollars in American Dollars. The search will return the currency rate as shown below.

Currency Conversion is one of the many special popular features of Google. At the time of writing, this handy feature is not available in both Yahoo! and Bing search engines.

Free Dynamic DNS with Custom Domain

2009-08-25T19:22:35Z

If you need to administer your home network remotely from office, you will either need to know the public IP address assigned by your ISP or use a service called dynamic DNS, that will map a DNS hostname to your IP address. Dynamic DNS is required as the public IP address assigned by your Internet Service Provider is never fixed for consumer broadband connections.

Dynamic DNS works by running a client program on your home PC or router, that will update the dynamic DNS servers whenever there is a change in the client IP address. This works great, but using a hostname such as foo.dyndns.org is not very pretty. I would rather use my own domain instead. Isn’t myhome.digitalinternals.com much better? But, to achieve this, you will need to allow the dynamic DNS service providers, such as DynDNS to administer your domain records. This is quite an hassle as this is probably managed by your web host. Such services are also not free.

To get around this problem, you will need a domain administrator or a webhost that allows you to add CNAME entries. A CNAME record is essentially a domain alias of another, canonical domain name. To get this working:

Sign up for a dynamic DNS account and register for a free subdomain.
Configure the dynamic DNS client in your router or PC.
Login to your webhost or domain administrator control panel and add a CNAME entry pointing to the dynamic DNS hostname you configured in step 1.

From this point onwards, any DNS lookups to myhome.digitalinternals.com will point to foo.dyndns.org, which in turn will return the dynamic IP address.