Comandos de la terminal/dd

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[rrc@Llawyr ComandosDeLaTerminal]$ dd --help
Usage: dd [OPERAND]...
  or:  dd OPTION
Copy a file, converting and formatting according to the operands.

  bs=BYTES        read and write up to BYTES bytes at a time
  cbs=BYTES       convert BYTES bytes at a time
  conv=CONVS      convert the file as per the comma separated symbol list
  count=N         copy only N input blocks
  ibs=BYTES       read up to BYTES bytes at a time (default: 512)
  if=FILE         read from FILE instead of stdin
  iflag=FLAGS     read as per the comma separated symbol list
  obs=BYTES       write BYTES bytes at a time (default: 512)
  of=FILE         write to FILE instead of stdout
  oflag=FLAGS     write as per the comma separated symbol list
  seek=N          skip N obs-sized blocks at start of output
  skip=N          skip N ibs-sized blocks at start of input
  status=WHICH    WHICH info to suppress outputting to stderr;
                  'noxfer' suppresses transfer stats, 'none' suppresses all

N and BYTES may be followed by the following multiplicative suffixes:
c =1, w =2, b =512, kB =1000, K =1024, MB =1000*1000, M =1024*1024, xM =M
GB =1000*1000*1000, G =1024*1024*1024, and so on for T, P, E, Z, Y.

Each CONV symbol may be:

  ascii     from EBCDIC to ASCII
  ebcdic    from ASCII to EBCDIC
  ibm       from ASCII to alternate EBCDIC
  block     pad newline-terminated records with spaces to cbs-size
  unblock   replace trailing spaces in cbs-size records with newline
  lcase     change upper case to lower case
  ucase     change lower case to upper case
  sparse    try to seek rather than write the output for NUL input blocks
  swab      swap every pair of input bytes
  sync      pad every input block with NULs to ibs-size; when used
            with block or unblock, pad with spaces rather than NULs
  excl      fail if the output file already exists
  nocreat   do not create the output file
  notrunc   do not truncate the output file
  noerror   continue after read errors
  fdatasync  physically write output file data before finishing
  fsync     likewise, but also write metadata

Each FLAG symbol may be:

  append    append mode (makes sense only for output; conv=notrunc suggested)
  direct    use direct I/O for data
  directory  fail unless a directory
  dsync     use synchronized I/O for data
  sync      likewise, but also for metadata
  fullblock  accumulate full blocks of input (iflag only)
  nonblock  use non-blocking I/O
  noatime   do not update access time
  nocache   discard cached data
  noctty    do not assign controlling terminal from file
  nofollow  do not follow symlinks
  count_bytes  treat 'count=N' as a byte count (iflag only)
  skip_bytes  treat 'skip=N' as a byte count (iflag only)
  seek_bytes  treat 'seek=N' as a byte count (oflag only)

Sending a USR1 signal to a running 'dd' process makes it
print I/O statistics to standard error and then resume copying.

  $ dd if=/dev/zero of=/dev/null& pid=$!
  $ kill -USR1 $pid; sleep 1; kill $pid
  18335302+0 records in
  18335302+0 records out
  9387674624 bytes (9.4 GB) copied, 34.6279 seconds, 271 MB/s

Options are:

      --help     display this help and exit
      --version  output version information and exit

Report dd bugs to
GNU coreutils home page: <>
General help using GNU software: <>
For complete documentation, run: info coreutils 'dd invocation'

[rrc@Llawyr ComandosDeLaTerminal]$ dd --version
dd (coreutils) 8.21
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Paul Rubin, David MacKenzie, and Stuart Kemp.

Respaldar el MBR con dd:

MBR Tomaño Total

    446 + 64 + 2 = 512


    446 bytes - Bootstrap.
    64 bytes - Tabla de Partición.
    2 bytes - Firma.

512 vs 446 Bytes

    Usa 446 bytes para sobre escribir o restorar tu /dev/XYZ MBR código de boot solo con los contenidos de tu archive de MBR.DD.
    Usa 512 bytes para sobre escribir o restorar tu /dev/XYZ con el MBR total que tiene Código de boot, la  Tabla de Partición y la firma.

dd comando para copiar MBR (entre solo dos discos con particiones identicales)

    dd if=/dev/sda of=/dev/sdb bs=512 count=1
El comando va a copiar 512 bytes (MBR) de sda a sdb. SOLO sirve si los discos tienen particiones identicales.

dd comando para dos discos de particiones de diferentes tomaños

    dd if=/dev/sda of=/tmp/mbrsda.bak bs=512 count=1
para restorar el imagen a cualquier sdb:
    dd if=/tmp/mbrsda.bak of=/dev/sdb bs=446 count=1

dd comando para creatr un boot USB de un ISO hybrido imagen
    dd bs=5M if=NombreDelImage.iso of=/dev/sdx
Debe asegurar que la lave USB NO está monteado

Para vaciar y limpiar un MBR:
  dd if=/dev/zero of=/dev/hda bs=512 count=1