This simple and brief tutorial will show you how to backup live CD or DVD to iso image on Ubuntu Linux using dd command.

dd is a command on Unix and Unix-like operating systems whose primary purpose is to convert and copy a file. On Unix, device drivers for hardware (such as hard disks) and special device files (such as /dev/zero and /dev/random) appear in the file system just like normal files; dd can also read from (and in some cases write to) these files. As a result, dd can be used for tasks such as backing up the boot sector of a hard drive, and obtaining fixed amount of random data.

To make iso image out of CD or DVD:

Insert your live CD or DVD into computer, then you can check the device name by running below command:

df -lh

You’ll get a similar output. The last line tells the device name /dev/sr0 and mount point /media/handbook/CD-Rom

Filesystem Size Used Avail Use% Mounted on
/dev/sda6 92G 47G 41G 54% /
none 4.0K 0 4.0K 0% /sys/fs/cgroup
udev 870M 4.0K 870M 1% /dev
tmpfs 176M 980K 175M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 878M 3.5M 874M 1% /run/shm
none 100M 56K 100M 1% /run/user
/dev/sr0 807M 807M 0 100% /media/handbook/CD-Rom

Now, use below command to create iso from it:

dd if=/dev/sr0 of=~/backup.iso bs=1000000 count=512 &&sync

Here if reads from file /dev/sr0, of write to file backup.iso, ~/ means user home directory. The value of ‘bs’ means read and write up to 1000000 bytes at a time.

For more, run:

man dd