Ddrescue: Ddrescue  is data recovery tool that copy data from one file or block device (hard disc, cdrom etc) and help out you to save data from crashed partition. It has decent ability to read the data and if it fails it will go on with the next possible sectors, where tools like dd will fail. If the copying process is interrupted by the user it is possible to continue at any position later. It can copy backwards too.

Install first the dd_rescue or ddrescue

If you are using RedHat/Fedora Core Linux, type the following command:

# yum -y install ddrescue

If you are using Debian Linux:# apt-get install ddrescue
Or directly download ddrescue from official GNU Web site. http://www.gnu.org/software/ddrescue/ddrescue.html

Make sure that Debian install ddrescue binary as /bin/dd_rescue and other distribution as /usr/bin/ddrescue

To make exact copy of /dev/sda (damaged) to /dev/sdb (make sure sdb is empty) you need to type following command:

# ddrescue /dev/hda /dev/hdb

Your further step is to run fsck on /dev/sdb partition to recover/save data. Remember do not touch originally damaged /dev/sda. If this procedure fails you can send your disk to professional data recovery service. For example if /home (user data) is on /dev/sda2, you need to run a command on /dev/sdb2:
# fsck /dev/sdb2
Once fsck run, mount /dev/sdb2 somewhere and see if you can access data:
# mount /dev/sdb2 /mnt/data
Now it is time to take backup using tar command.
ddrescue command supports many options. Just to remind you, Don’t forget to read man page:
# man ddrescue OR # man dd_rescue

* IPv4:  Internet Protocol version 4 (IPv4) is widely used by most of the Internet servers and personal computers. This uses 32 bits to assign a network address as defined by the four octets of an IP address up to 255.255.255.255. Which is the representation of four 8 bit numbers thus totaling 32 bits.

* IPv6: Internet Protocol version 6 (IPv6) uses a 128 bit address and thus billions of potential addresses. The protocol regularly upgraded to include new quality of service features and security. Linux supports both IPv6 but IPv4.

* TCP/IP: (Transmission Control Protocol/Internet Protocol) uses a client – server model for communications. The protocol defines the data packets transmitted, re-transmission. data integrity verification (error detection bytes), connection and acknowledgement protocol.

* TCP/IP time to live (TTL): This is a counting system to determine how long a packet is valid before it reaches its destination. Each time a TCP/IP packet passes through a router it will decrease its TTL count. After the count reaches zero the packet is dropped by the router. This ensures that delinquent routing and looping aimless packets will not flood the network.

* MAC Address: (media access control) is the network card address used for communication between other network devices on the subnet. This info is not routable. The ARP table maps TCP/IP address (global internet) to the local hardware on the local network. Use the command /sbin/ifconfig to view both the IP address and the MAC address. The MAC address distinctively recognizes each node of a network and is used by the Ethernet protocol.

* OSI 7 Layer Model: The ISO (International Standards Organization) has defined the OSI (Open Systems Interconnection) model for current networking protocols.

* Full Duplex:  Full Duplex allow sending and receiving of packets instantaneously. Most modern modems support full duplex.

* Half Duplex: Allows the sending and receiving of packets in one direction at a time only.

SHOUTcast consists of a client-server model, however you should not run it as root because it can prone to security issue, instead you should create a shoutcast user:

How do we install shoutcast?

1.) Login to root through SSH on the server.
2.) adduser shoutcast
3.) passwd shoutcast
Login as the new shoutcast user, or you can su to the user.

su shoutcast

Download shoutcast from nullsoft:
1. http://www.shoutcast.com/downloads/sc1-9-2/shoutcast-1-9-2-linux-glibc6.tar.gz
Lets extract shoutcast:
2. tar -zxvf shoutcast-1-9-2-linux-glibc6.tar.gz
Lets tidy up the directory:
3. rm -rf shoutcast-1-9-2-linux-glibc6.tar.gz
mv shoutcast-1-9-2-linux-glibc6 shoutcast
cd shoutcast
Shoutcast has now been installed!

configure shoutcast on following step;

Now edit the configuration file.
pico sc_serv.conf
or you can use vi which I prefer, a bit more advanced to use.
vi sc_serv.conf
You can set some important configureation options. Change these settings in the file:
MaxUser
Password
PortBase
uncomment AdminPassword and set an admin password.

Now going through the settings, you can change them to what you want or you can save and start shoutcast and it will work now.
to save crtl+x (if using pico) or :wq if using vi
Now you can start shoutcast here;

./sc_serv sc_serv.conf

How to transfer data with rsync;

To take back up or transfer data of one or more folder here is the guideline by which you can do it using command rsync. A folder of which you want to take back up is called as source directory and folder where you are taking the backup is called as destination folder.
Let’s assume that you have two folders. First one is backup_source and another is backup_destination.
backup_source is a folder of which you have to take backup into folder backup_destination.
run the simple command to accomplish the task.
rsync -ave backup_source/ backup_destination/
This is simple way from which you can take backup.
Now let us understand the options use in command
1)-a, –archive archive mode; same as -rlptgoD (no -H)
Instead of using several options like -rlptgoD, you can use just a option which is equivalent to the said options.
-r, –recursive recurse into directories
-l, –links copy symlinks as symlinks
-p, –perms preserve permissions
-t, –times preserve times
-g, –group preserve group
-o, –owner preserve owner (super-user only)
-D same as –devices –specials
2)-v, –verbose increase verbosity
3)-e, –rsh=COMMAND specify the remote shell to use

Use the following command especially if you want to take backup from another machine over secure shell.
rsync -ave ssh username@anothermachine/backup_source/ backup_destination