badblocks - search a device for bad blocks


SYNOPSIS

       badblocks [ -svwnf ] [ -b block-size ] [ -c blocks_at_once
       ] [ -i input_file ] [ -o output_file ] [ -p  num_passes  ]
       device [ last-block ] [ start-block ]


DESCRIPTION

       badblocks  is  used  to  search for bad blocks on a device
       (usually a disk partition).  device is  the  special  file
       corresponding  to  the device (e.g /dev/hdc1).  last-block
       is the last block to be checked; if it is  not  specified,
       the last block on the device is used as a default.  start-
       block is an optional  parameter  specifying  the  starting
       block  number  for  the  test, which allows the testing to
       start in the middle of the disk.  If it is  not  specified
       the first block on the disk is used as a default.


OPTIONS

       -b block-size
              Specify the size of blocks in bytes.

       -c number of blocks
              is the number of blocks which are tested at a time.
              The default is 16.   Increasing  this  number  will
              increase  the efficiency of badblocks but also will
              increase its memory usage.  Badblocks needs  memory
              proportional  to  the  number  of  blocks tested at
              once, in read-only mode, proportional to twice that
              number  in  read-write  mode,  and  proportional to
              three times that number  in  non-destructive  read-
              write mode.  If you set the number-of-blocks param­
              eter to too  high  a  value,  badblocks  will  exit
              almost  immediately  with  an  out-of-memory  error
              "while allocating buffers".  If you set it too low,
              however,  for  a  non-destructive-write-mode  test,
              then it's possble for  questionable  blocks  on  an
              unreliable  hard  drive to be hidden by the effects
              of the hard disk track buffer.

       -f     Normally, badblocks will refuse to do a  read/write
              or  a  non-destructive  test  on  a device which is
              mounted, since this can cause the system to  poten­
              tially  crash.   This  can be overriden using the -
              flag, but this should not be done under normal cir­
              cumstances.   The  only time when this option might
              be safe is if the /etc/mtab file is incorrect,  and
              the device really isn't mounted.

       -i input_file
              Read  a  list of already existing known bad blocks.
              Badblocks will skip testing these blocks since they
              are known to be bad.  If input_file is specified as

              Blocks listed in this list will be omitted from the
              list of new bad blocks  produced  on  the  standard
              output  or  in  the  output file.  The -b option of
              dumpe2fs(8) can be used to  retrieve  the  list  of
              blocks currently marked bad on an existing filesys­
              tem, in a format suitable for use with this option.

       -o output_file
              Write the list of bad blocks to the specified file.
              Without this option, badblocks displays the list on
              its  standard  output.   The format of this file is
              suitable for use by the -l option in  e2fsck(8)  or
              mke2fs(8).

       -p num_passes
              Repeat  scanning  the  disk  until there are no new
              blocks discovered in num_passes  consecutive  scans
              of  the disk.  Default is 0, meaning badblocks will
              exit after the first pass.

       -n     Use non-destructive read-write  mode.   By  default
              only  a  non-destructive  read-only  test  is done.
              This option  must  not  be  combined  with  the  -w
              option, as they are mutually exclusive.

       -s     Show  the  progress  of the scan by writing out the
              block numbers as they are checked.

       -v     Verbose mode.

       -w     Use write-mode test. With  this  option,  badblocks
              scans  for  bad  blocks  by  writing  some patterns
              (0xaa, 0x55, 0xff, 0x00)  on  every  block  of  the
              device,  reading every block and comparing the con­
              tents.  This option may not be compiled with the -n
              option, as they are mutually exclusive.


WARNING

       Never  use the -w option on an device containing an exist­
       ing file system.  This option erases data!  If you want to
       do  write-mode testing on an existing file system, use the
       -n option instead.  It is slower,  but  it  will  preserve
       your data.


AUTHOR

       badblocks  was written by Remy Card <Remy.Card@linux.org>.
       Current maintainer is Theodore Ts'o  <tytso@alum.mit.edu>.
       Non-destructive read/write test implemented by David Beat­
       tie <dbeattie@softhome.net>.


AVAILABILITY

       badblocks is part of the e2fsprogs package and  is  avail­
       able from http://e2fsprogs.sourceforge.net.

       e2fsck(8), mke2fs(8)


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