Posts tagged mbr

dd Howto and some MBR tricks

posted on 2014-05-09 19:00:18

dd is used to "convert and copy files" under linux.

Basic Stuff

Read: Use it for disk images. I.e. put an .ISO on an USB stick. Or copy whole HDD's. Or create ISO's.

# use 'mount' to find out where the stick is mounted

# copy iso onto usb stick
dd if=<isoname>.iso of=/dev/sdX

# create an iso
dd if=/dev/cdrom of=/home/<username>/Desktop/<isoname>.iso

# wipe clean
dd if=/dev/zero of=/dev/sdX

# make a file of 100 random bytes
dd if=/dev/urandom of=/home/<username>/my.random bs=1 count=100

That was it with the usual suspects. Now onto more serious stuff.

Serious Stuff

# PRO: create image from one host and stream to the other
#on target host
netcat -l -p 1234 | dd of=/dev/hdc bs=16065b
#on source host (where the ISO will be created and streamed)
dd if=/dev/hda bs=16065b | netcat <targethost-IP> 1234

#or use this:
# from remote to local
rsh 192.168.xx.yy "dd if=/dev/sda ibs=4096 conv=notrunc,noerror" | dd of=/dev/sda obs=4096
# or from local to remote
dd if=/dev/sda ibs=4096 conv=notrunc,noerror | (rsh 192.168.xx.yy dd of=/dev/sda obs=4096)

In the above you may use ssh, or rsh. Do as you please. Of course you may use different IP's.

And now...

Very Serious Stuff

# PRO: show your MBR
dd if=/dev/sda count=1 | hexdump -C

# PRO: back up MBR
dd if=/dev/sda of=mbr.bin count=1

    #put this on a floppy you make with
    dd if=boot.img of=/dev/fd0
    #along with dd. Boot from the floppy and
    dd if=mbr.bin of=/dev/sda count=1
    #will restore the MBR.


# PRO: command to read your BIOS and all interfaces
dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8

on decrypting an MBR

Use file. Just do it:

dd if=/dev/sda of=mbr.bin
file mbr.bin

will give you something like this:

mbr.bin: x86 boot sector; partition 1: ID=0xee, starthead 0, startsector 1, 234441647 sectors, extended partition table (last)\011, code offset 0x0

which is easily read and understandable.

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