How to Run a remote Linux desktop in Windows

There are only two pieces of software necessary:

1)x11vnc: Installed on the Linux machine to use as the VNC server.

2) TightVNC: Installed on the Windows machine to use as the VNC client.

Installing the windows software is straight forward for most users. Just download the installer and double click. For many Windows users, the installation of the Linux software might not be as straight-forward.
Of course the Linux installation will depend upon your distribution. But basically all you have to do is follow these steps:
1. Open up your Add/Remove Software tool (such as Synaptic, Ubuntu Software Center, gnome-packagekit, etc)
2. Search for "x11vnc" (no quotes)
3. Select the results for installation.
4. Click Apply to install.
Now, if you are more comfortable with the command line you can install the Linux software like so:
1. Open up a terminal window.
2. Issue a command like sudo apt-get install x11vnc (this will depend upon the distribution you use).
Once all of the software is installed, you are ready to go.


The Linux side
This is really quite easy. All you need to do is start the x11vnc server. If you look at the manual page for x11vnc (issue the command man x11vnc) you will see numerous options available for the server. One of those options you might want to consider is the -forever option. If you don't add this option to the command your x11vnc server will die as soon as the client quits the session.
So the command you will want to run, from the terminal, is:
x11vnc -forever
You will notice you do not get your prompt back. Even if you add the & character, x11vnc will not return you your prompt. Because of this, you might want to consider adding a line like x11vnc -forever to the end of your /etc/rc.local file. This will ensure your x11vnc server is started at boot.


The Windows side
Now it's time to connect. You've already installed TightVNC on the Windows machine so go to the Start menu and fire up TightVNC. When you open the tool up a small window will appear that allows you to enter an address for the connection as well as open up the Options window.

Read more »

What are the layers in OSI model?

The OSI model consists of seven layers, as follows (working from the bottom up):

Physical layer: This is the layer where the network hardware operates. Rules for this layer govern the
types of connectors used, what types of signaling techniques carry data across the network, and the
types of cable or other networking media that the physical, tangible part of the network uses. In some
sense, this is the only part of the OSI model that you can see and touch.

Data Link layer: This layer handles communication with the network hardware. For outbound
messages, the Data Link layer enables the conversion of the bits that computers use to represent data
into equivalent signals needed to move data across the network. For inbound messages, it reverses
the process by enabling the conversion of signals into their equivalent bits. The Data Link layer is also
where low-level hardware addresses for individual network interface cards (NICs) and other devices
are handled.


Network layer: This layer routes messages between senders and receivers, which means that it also
handles translation between human-readable network addresses and computer-readable network
addresses (which are not the same as the hardware addresses that the Data Link layer handles).
Each message that passes through this layer includes the sender's and the receiver's addresses to
identify the parties involved. The Network layer moves data from sender to receiver when they aren't
both attached to the same cable segment.

Transport layer: This layer chops up large messages into so-called Protocol Data Units (PDUs), or
packets, and sends them across a network. It also puts PDUs back together to reconstitute messages
upon receipt. The Transport layer can also include data integrity checks by adding a bit pattern to each
message based on a mathematical calculation before sending. This same calculation is repeated by
the sender, and the result is compared to the value calculated beforehand. If both values agree, the
Transport layer assumes that the transmission was accurate and correct; if they don't agree, the
Transport layer requests that the PDU be resent. This integrity function is optional; therefore, some
Transport layer protocols include an integrity check and others don't.

Session layer: This layer sets up ongoing network conversations (called sessions) between sender
and receiver. This kind of ongoing connection makes it easier for computers to exchange large
amounts of data, or to maintain a connection when data moves regularly between both parties to a
session. Therefore, the Session layer handles session setup (which is like dialing a phone), session
maintenance (which is like having a phone conversation), and session termination, or teardown (which
is like ending a phone conversation and then hanging up the phone).

Presentation layer: This layer converts data for network delivery. The assumption that drives this
activity is that the sender and the receiver may not share a common set of data types, formats, or
representations. Therefore, the Presentation layer converts data from formats created by the sender
into a generic format for network transit, and then converts that generic form into a format specific to
the receiver upon delivery. This conversion process allows programmers on both sides of the network
connection to assume generic formats for network data, and to handle the details necessary to deliver
that data to a specific client more easily.


Application layer: This layer's name is something of a misnomer. It doesn't refer to the application or
service that seeks to send or receive data across a network. Rather, it refers to an interface between
the protocol stack and applications or system services. The Application layer defines the methods by
which applications or system services can request network access and by which they can obtain
access to incoming data from the network.

Read more »

What are the tools used in Active Directory?

Active Directory Domains and Trusts:

• Implementing trusts
• Raising domain/forest functional levels
• Adding user logon suffixes

Active Directory Sites and Services:

• Configuring intrasite/intersite replication
• Configuring global catalog
• Creation of sites, site links, subnets.
• Scheduling replication

Active Directory Users and Computers:

• Managing users/groups
• Managing computers.
• Managing OUs
• Managing Group Policy (Domain Level)
• Managing Operations masters.
• Raising domain functional level.

Domain controller security policy:

• Set account, audit and password policies
• Set user rights
• Permissions or policies Pertains only to the DC where you set.

Domain security policy:

• Set account, audit and password policies
• Set user rights
• Permissions or policies pertain to the DC as well as to all the domains within.

Read more »

How to remove Active Directory?

Safe removal of A.D.
>Start >run >dcpromo

Forceful removal of A.D
>Start >run > dcpromo / forceremoval

Read more »

What are the main features of Active Directory?

1. Fully integrated security system with the help of Kerberos.
2. Easy administration using group policy.
3. Scalable to any size n/w
4. Flexible (install/uninstall)
5. Extensible (modify the schema)
New features in Server 2003
6. Rename computer name & Domain names.
7. Cross –forest trust relationship.
8. Site-to-Site replication is faster.

Read more »