The ‘ dd ‘ command is one of the original Unix utilities and should be in everyone’s tool box. It can strip headers, extract parts of binary files and write into the middle of floppy disks; it is used by the Linux kernel Makefiles to make boot images. It can be used to copy and convert magnetic tape formats, convert between ASCII and EBCDIC, swap bytes, and force to upper and lowercase.
# dd –help
full hard disk copy
dd if=/dev/hdx of=/dev/hdy
dd if=/dev/hdx of=/path/to/image
dd if=/dev/hdx | gzip > /path/to/image.gz
dd if=/dev/hdx of=/dev/hdy
dd if=/dev/hdx of=/path/to/image
dd if=/dev/hdx | gzip > /path/to/image.gz
Hdx could be hda, hdb etc. In the second example gzip is used to compress the image if it is really just a backup.
Restore Backup of hard disk copy
dd if=/path/to/image of=/dev/hdx
dd if=/path/to/image of=/dev/hdx
gzip -dc /path/to/image.gz | dd of=/dev/hdx
MBR backup
In order to backup only the first few bytes containing the MBR and the partition table you can use dd as well.
dd if=/dev/hdx of=/path/to/image count=1 bs=512
MBR restore
dd if=/path/to/image of=/dev/hdx
Add “count=1 bs=446” to exclude the partition table from being written to disk. You can manually restore the table.
“All This Information was taken from the other site , just for information to take hard-disk backup , it will be useful to use it with Oracle ”
thank you
Osama mustafa
Technology Geek 