command dd

info

1. dd command copies a file

   1. converting the format of the data in the process

   2. according to the operands specified

operands

1. bs read and write bytes at a time

   1. ibs read bytes at a time (default 512)

   2. obs write bytes at a time (default 512)

2. cbs convert bytes at a time

3. conv comma separated symbol list

   1. ascii from ebcdic to ascii

   2. ebcdic from ascii to ebcdic

   3. ibm from ascii to alternate ebcdic

   4. block unblock lcase nocreat excl notrunc ucase swab noerror sync fdatasync fsync

4. count copy only input blocks

5. if read from file instead of stdin

6. of write to file instead of stdout

demo

1. from computerhope

   1. create a iso disc image from cd

       $ dd if=/dev/sr0 of=/home/hope/example.iso bs=2048 conv=noerror,sync
      

   2. create an img file of /dev/sda hard drive

       $ dd if=/dev/sda of=~/disk1.img
      
       # restore that image
       $ dd if=disk1.img of/dev/sda
      

   3. copy contents

       $ dd if=/dev/sda of=/dev/sdb
      

2. from tuxgarage

   1. create a startup usb from a hybrid image

       # !!!!!
       # warning: make sure to set the correct device path
       # as this process will delete all data
       # that was on the specified device previously
      
       # !!!!!
       # don't include an integer for the usb drive
       # e.g. `/dev/sdx1` as it would refer to
       # `the existing partition` on the drive
       # not the drive itself
      
       $ dd if=~/Desktop/ubuntu-15.04-desktop-amd64.iso of=/dev/sdx oflag=direct =1048576
      
       # figure out the target usb drive path
       $ fdisk -l
      

3. from osxdaily

   1. convert a dmg file to iso

       $ hdiutil convert imagefile.img -format UDTO -o converted.iso
      

   2. convert an iso to dmg

       $ hdiutil convert converted.iso -format UDRW -o imagefile.img