Monday, December 12, 2011

Backup an entire hard disk using dd command

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

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

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  

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