how to backup MBR with dd?

[cb88]

how can I backup my MBR with dd and restore it later with dd?

assume that i have a flash drive to save the image to running from the livecd...

[Bruce B]

backup
cd to your flash drive
dd if=/dev/hda of=backup.mbr bs=512 count=1

restore
cd to your flash drive
dd if=backup.mbr of=/dev/hda count=1

[cb88]

so i guess that means dd if=infile and of=outfile bs=512 (512 byte bootsector) count=1 (not sure)

that makes sence thanks

[Bruce B]

so i guess that means dd if=infile and of=outfile bs=512 (512 byte bootsector) count=1 (not sure)

that makes sence thanks

I'm glad it makes sense, because dd doesn't follow Linux conventions for parameters very closely.

In this example count=1 says, "Start at the first sector and take the amount of data defined in bs=, and quit after doing it one time."

In common language it says, "Write (copy) a file containing the first 512 bytes on the first sector of /dev/hda, which happens to be the MBR, and that's because we know in advance where the MBR is located and how big it is."

If count=10 it would start at the first sector and copy 512 bytes sequentially up the sectors ten times. The file size would be 5120 and it would contain more than just the MBR.

[Flash]

Thanks for that explanation Bruce. It demystifies the dd command somewhat.